Oil Flow to Go

Engines are expensive. Helping them last is important for every race team and finding extra horsepower is always a gift that keeps on giving. For horsepower and longevity, the oil system pumps black gold through the veins of your car while facing extremely demanding conditions. Dry sump pumps are the heart of many race engines and understanding a few basics will allow the heart of your car to extend the life of your engine while maximizing power.

A Remote Oil Filter Mount allows teams to locate the oil filter nearly anywhere. A mount that rotates will compensate for bars that run on an angle so you can keep the filter level.

AC Nutter is an engine builder that builds high horsepower engines that have won numerous championships. AC has earned his reputation as a top builder through hard work and self learned creativity. Nutter engines include many ideas developed by AC through his years of hands on experience with top race teams. To support his Nutter engines, AC felt he could help his teams by designing and manufacturing his own dry sump pumps. The combination of being an engine builder and a pump manufacture gives him a unique perspective in understanding how to feed engines with oil properly.

What are your thoughts on a dry sump venting system?

Nutter:

With a dry sump, the vent system must be designed to allow the engine to breath. A proper vent system prevents leaks and keeps precious oil in the car. Too often, tracks are oiled down due to venting system problems. With a three stage pump, it is a good idea to vent the engine valve covers along with the oil tank. You can use breathers on the valve covers or run a line from the valve cover to the tank and use the same vent for both the engine and the dry sump tank. I agree with AC and from my experience vent systems experience less trouble when you run a #12 line from the valve cover back to the tank and let the system breath with a vent back at the dry sump tank.

If you need to vent your engine at the valve cover, a breather kit can easily be welded at a location that allows teams to install the engine without impacting chassis bars.
Nutter:

With a 4 stage dry sump pump, only the tank needs to be vented due to the added vacuum created by the additional stage. Utilizing a small baffled breather tank, with a vent on the top, nearly eliminates venting issues. Be sure to mount the breather tank as high as possible and as far to the left as you can. Connect the dry sump tank to your breather with quality hose. G force will help force oil that collects in the vent tank back down into the dry sump tank. With the breather tank mounted high, there is enough line length to allow gravity to keep the line clear so air can pass through easily. Be sure to avoid any droops in the vent hose to prevent oil from pooling in a low spot. Pooled up oil in a line can prevent the block the vent creating an oil mess that can potentially take you out of a race.

A good Oil Filter Cutter allows you to quickly cut open paper style filters. A quick inspection allows teams to find particles and debris that may indicate a serious engine problem. Paper filters are excellent at filtering out fine particles and are often used in conjucntion with cleanable mesh style filters.

With a dry sump – what do you recommend for line sizes?

Nutter:

The line size question is a big one with many variables and lots of diffenent answers. The most common system would be #12 lines from the pan to the pump. #12 is used to feed oil to the engine with a #16 line to provide a free flow of oil to the tank. Often, I think a #10 line from the pan to the pump is a better way as it provides more overall vacuum and improved performance.

How many stages do you need in a dry sump pump?

Nutter:

My first answer is to let your engine builder decide. Most engines that require a dry sump are in the high end category and your engine builder will understand all the variables that apply to your type of racing. Rules come into play as well and an experienced engine builder can design a dry sump package that meets the needs or your rules, race series and budget. On the surface, this seems like an easy question but there is much to consider and your engine builder will have a philosophy that creates an oiling system that meets the needs of your engine package and series requirements.

A three stage pump supplies ample oil to the engine. A four stage pump creates more vacuum. The added vacuum moves oil away from the rotating crankshaft assembly, producing more horespower.

For a general answer, a three stage dry sump system works as well as a four stage system when it comes to prolonging engine life. 3 stages are plenty adequate to provide a steady supply of fresh oil to the engine. 3 stages obviously saves cost over additional stages as the pump cost is less and the car plumbing is simplified. Your team saves the work and the expense of added lines and AN fittings – those things add up in the cost column.

However, four or more stages will create more horsepower. 3 stages supply oil to your engine just fine – the added stages create vacuum in the oil pan and crank case area. Vacuum causes the oil to lie down in the pan to be efficiently picked up by the dry sump pump scavenging system. With the excess oil pulled down in the pan, oil is not picked up by the rotating crank and rods that spin at high RPM. Reducing the amount of oil that gets wrapped around the rotating assembly, results in horsepower gains. The engine can simply spin more freely.

Oil splashing around the pan and onto the rotating assembly robs horsepower. A fourth dry sump stage creates vacuum and reduces the amount of oil that splashes around inside your engine allowing the rotating assembly to rotate freely. Oil is thick and viscous. If the crank assembly has to beat its way through a pig pool of oil it will have to work harder. The beating action reduces oil life and can cause unwanted foaming. Basically, it is easier to walk down the street than it is to walk neck deep in a swimming pool. By removing oil from the pan, by utilizing vacuum created by the dry sump pump, you will find gains in horsepower. In our testing, we have found as much as 12 additional horsepower with a 4 stage dry sump pump as the rotating assembly can spin without having to fight through a pool of oil in the bottom of the pan.

Creating 8 to 12 inches of vacuum is all that is required to keep the rotating assembly free of excess oil. If your engine runs low tension oil rings you might need 18 inches of vacuum, or more, to keep oil away from the rotating assembly. Your engine builder can assist in making decisions. Something as simple as changing oil ring tension has an effect on the dry sump pump system and the vacuum needs are completely different depending on the ring design you run. Customers will experience less engine trouble if they recognize that a high performance engine is a package and even small changes can be interrelated – one thing affects another and each change needs to be thought completely through.

What do you consider in a dry sump system?

Nutter:

When using dry sump pumps you need to consider the entire oil system. Just a few considerations are dry sump reserve tank size, vent tank type and size, number of stages needed, plumbing line sizes and more. Pan design is a very important element. When it comes to oil pan designs, you want to use a pan that is as wide and deep as possible.

A Dry Sump Breather Tank should be mounted high so oil can easily flow back to the tank. Lines should be routed free of droops so oil can't pool up and plug the venting system. This tank has a drain valve in the bottom so teams can verify that oil is not backing up in the oil system.
Scavenge filtering and engine oil filters must be considered. I prefer oil filters without a bypass. The dry sump pump mounting and drive system varies from car to car and choices must be made that ensure that your dry sump pump is mounted securely with a drive system that will perform 100% of the time. Nearly every dry sump pump on the market is of good quality. I recommend that teams purchase what they can afford and design an overall system that mates up with their rules while placing emphasis on their individual budget. It does little good to install a system that you can’t afford to maintain. In general, the more you spend on a dry sump pump then the more expensive it is going to be to maintain.

What to your recommend for oil filtering?

Nutter:

Paper filters clean oil just fine. Cleanable filters provide the added benefit of allowing you to easily check your engine for debris. Early identification of particles in the filter can save big money on repairs. I like a 60 micron filter with no bypass. If the filter plugs, the oil pressure will drop and your gauge will warn you that there is a problem. The same warning gauge has no way of telling you that dirt is going through the engine so a bypass is a not something I use on my engines.

For the scavenge filter I like a 60 micron filter for the initial start up on a new engine. After a proper warm up, I install a 100 micron scavenge filter before he car goes out on the track.

What about dry sump servicing?

Nutter:

Anytime you freshen or repair the engine you should service the pump. Dry sump pumps are designed so that there is not much that goes wrong. Basically, go through the pump whenever you go through the engine so that you can make sure that the pump was not damaged by a past engine problem. If you have just freshened your engine, then of course you want to protect your investment by ensuring the pump is up to spec.

What about engine oil?

Nutter:

One thing I believe in is that on most engines I like to use thin oils. You should certainly consult with your engine builder but, for my stuff 20 weight oil is most common and 30 weight is the absolute maximum.

Butcher:

By thinking out your dry sump system, you can increase your engine life and find more horsepower. The investment pays off in less rebuilds and improved performance. If your rules allow it then a dry sump pump is highly recommended. Quality oil can be thin and a vent system that supplies clean air to your engine will help your car to flow straight to the front.

Go Forward – Move Ahead
Jeff Butcher

10/1/11

Keeping It Cool

As cars go faster, air openings feed engines with an ever decreasing amount of air. Watching Bobby Allison slide his Penske Matador through the turns on a half mile or at Daytona was cool – the engine had plenty of air for cooling and the Matador nose could double as a snow plow during a heavy Michigan winter. In those days, the front opening on the car was so big you could use a racecar grill for a BBQ cook top that would hold enough steaks to feed the entire Allison clan.

Adjustable radiator mounting brackets allow for quick experimentation. The roll bar clamp on brackets lets teams adjust the mounting angle quickly. Down force and radiator surface area can be optimized in seconds. Over time, teams can identify the optimal mounting position utilizing hardware that is designed to promote easy adjustment.

Going back in time, stock cars were built to bump, grind and to slide around - aero down force was reserved for Formula 1 and Indy. Dents in the fenders had little effect on speed. Today, an 1/8” variation on a stock car front fender width can take the car from loose to an aero push with the slightest of bumps. Grill of today perform only one hot dog at a time.

A Penske Matador, with an Allison at the wheel, could actually use muscle to power on to victory lane. Cars that rely down force are required to baby their way around the track and the grill opening feeds a finely metered amount of air to the radiator. While old school was more fun, it seems we are stuck with finding more aero advantage and driver muscle is reserved for Sharpie’s and autograph lines.

Since it seems unlikely that stock car grills will be coming out of ’55 Chevy’s anytime soon, teams face the challenge of keeping the engine at optimal operating temperature while maintaining an anorexic grill opening. The optimal grill shape - thin with nothing other than well placed tape directs air precisely. You would think stock cars were getting ready for the Red Carpet and Hollywood Paparazzi verses lining up for the starting grid.

When it comes to the coolant system, proper radiator mounting is an area where cooling can be maximized and speed can be gained. From experience, with plenty of room for debate depending on the car type and track, 7 degrees of forward mounting angle at the top of the radiator increases the radiator surface area while producing additional front down force. Air ducting from the grill opening needs to be tightly sealed and shaped properly to provide maximum cool air while traveling through a minimum space.

Radiator duct panels should be wide and flat (nearly parallel to the ground) at the bottom. Extending the bottom panel of the radiator duct work out at the nose piece is a “semi-legal cheat” that helps seal the nose area of the car with a “belly pan” that is disguised as radiator duct work.

Often, teams build the grill duct work the same width as the radiator. By extending the width of the bottom panel at the front of the car, you can gain some down force by using the bottom sheet metal radiator duct panel, at the nose piece, wider than the radiator. The duct work sides can still seal at the grill opening extending back to the radiator. Proper radiator duct shape enhances air movement for efficient cooling. “Stretching” the bottom panel outside of the grill width gains you a few inches of belly pan and it is likely that it won’t be noticed by the competition and often gets through tech without issue.

At the nose, the top panel of the radiator duct work should start nearly parallel to the ground with a few degrees of upward angle for the first 6” or so to reduce lift. The top panel transition, after the first 6” or so, should smoothly round up to the top of the radiator producing maximum cooling while producing extra down force. Working the ducting shape in your favor can provide for better down force numbers while improving cooling efficiency.

Since reliance on aero for handling is here to stay, then teams must find ways to manage consistent and controllable engine temperatures while striving for the minimum front end air opening. A variety of options are available to keep things cool in the heat of battle. Like all things in racing, finding many small areas of advantage works much better than hoping for a fix that comes from a single magic source.

IR pyrometers can help teams to identify hot spots providing an opportunity to direct air through duct work to critical areas in the cooling system. Isolating potential hot spots with an IR pyrometer can display areas where more air flow or improved radiator duct shapes will help to drop water temperatures.

An Infrared Pyrometer can be utilized to instantly measure cooling system adjustments. As teams experiment with their coolant system efforts, the IR pyrometer can be used to spot check multiple system locations with precision. Improvements can be recorded and experiments that have a detrimental effect can be quickly rectified by taking multiple measurements with an IR pyrometer.

When experimenting with radiator ducting shapes an IR pyrometer can help you determine if you are making gains. Assuming you are at the same track, with the same outside ambient temperature, you can take an IR reading on piece of sheet metal that is temporarily mounted behind the radiator and in front of the engine. The is plenty of room for error with this method but, if you can repeat the number of laps, time it takes to get to the car, outside air temps and as many variables as possible then you can find improvements over time by taking an IR reading on your test sheet metal and compare temperature changes based on the changes you make.

Examples of cut and try items for improved cooling are radiator mounting angle, radiator duct shapes, grill tape and more. Since short track racers have limited engineering and testing time of Cup teams, it may take weeks to learn which experiments are producing positive results. Still, gains can be found if you are willing to cut and try and spend more time than your competition.

Freeze plug adaptors allow racers to tap the water system, changing flow as needed. With the right hardware water flow can be managed to meet any requirement.

Quality water temperature gauges will provide you great information relating to the average temperature of your coolant. If the IR pyrometer helps you to identify a hot spot in the engine compartment then directing air precisely can help to lower the overall under hood temperature created by outside forces. Saving money on a water temp gauge may seem like a good idea but to produce long lasting horsepower your team must work with your engine builder to identify operating temperatures that produce maximum horsepower. Accuracy is needed to monitor temps to create the ultimate horsepower available.

Locating your water temp gauge probe in the ideal position can help your team to find the “ideal” measuring location. Temperature Tee’s can be installed in line in selected water hoses helping you to measure how your innovative ideas relating to water temperature are performing. For testing purposes, more than one water temp gauge can be installed and your team can use multiple Temp Tee fittings in line on various hoses. Multiple water temp gauges can be used for testing so your team can get take measurements of the water system at critical locations. By checking your water temps in strategic locations, your team can visually see how water treatment ideas are working out.

Temperature Tee's come in a variety of line sizes and allow water temp gauge probes to be located in nearly any location in the cooling system. Successful teams experiment by connecting multiple Temperature Tee's in several locations. Using  multiple water temp gauges at key system locations can help you to sort out coolant system issues.

Some engine builders route engine water to manage temperatures at precise locations. Freeze plug adaptors provide easy access to tap into the water system and hoses can be easily installed to route water as needed.

Coolant additives can help the longevity of your cooling system components. Anti corrosives and lubricating properties can be a big benefit and even save money over the long haul. Water cooling claims made by additive manufactures should be considered by each customer and their specific needs – a well designed system is needed and simply pouring in an additive will do little to fix a system that is designed poorly.

Ported Water Outlet fittings, at the intake manifold, are another area where the coolant system can be easily tapped to improve water flow. Adding a Thermo Spacer provides a clean mounting location for water temp senders right at the engine intake – temps taken as water enters your engine provide a great way to verify if your water cooling efforts are headed in the right direction. The additional ports, in Ported Water Outlet Fittings, allow racers to direct water flow to meet nearly any requirement.

Ported Water Outlet fittings can be located right at the intake manifold and are a reliable place to monitor cooling system improvements. Extra ports allow for a quick tap of the water system to directing needed coolant in a simple fashion. An O-ring seal ensures that your system stays water tight.

On cool nights, more grill tape may be needed to get your engine up to operating temp. Heat is horsepower and I can think of many early spring nights where the grill opening was nearly sealed off completely. The added front down force made the car faster as long the corresponding amount of rear down force was added. Down force nearly always wins out over aero drag on short tracks.

A water expansion tank with a Billet Cap Flange has the muscle to perform. Utilizing high pressure lines and quality water coolant components allows teams to run maximum cap pressures. A Billet cap connections ensures a perfect seal as compared to stamped aluminum cap flanges that can fail under pressure.

Optimizing horsepower, by keeping the water temperature in heat range that creates the most horsepower, is managed on a race by race basis. Tape, jetting, fans and the like are tailored based on the conditions that vary each week – sometimes each hour.

A Thermo Spacer, used at the intake manifold, provides easy access to the water system. Creativity can be maximized while maintaining a clean and professional installation. O-Rings keep the water in your engine so your team can focus on making more power.

Competition gets tougher every week and teams that strive to find the smallest gains win more often. I deal with Cup teams that have custom parts made that save only 1 gram of weight. As short track racers, we often think of saving pounds at a time. Cup teams use the finest resolution possible and think in terms of saving a single gram. Over time, the single grams saved pile up and the result is a car that is as light as possible. The same philosophy applies to the cooling system. The teams that strive to explore cooling system improvements will beat the heat and their teams will run consistently hot.

Go Forward – Move Ahead

Jeff Butcher

8/1/11

Proper Tire Prep & Purge

If you are into skinning cats, you will find that there are more ways to get racecars around corners than there are cats to skin. On the other hand, skins on racecars are what connect your secret set up to the ground. More adhesion at the contact patch creates long lasting speed. Balancing the grip at all 4 corners produces a fast car and any talk of skins can be limited to tires – you can leave the cat lady alone. Maintaining desired tire size is critical when it comes to being catty enough to win.

Managing tires can be a daunting task. Keeping good notes and having the proper tools for measuring and purging saves valuable time and is often the difference that gets your team the big win.

Bias Ply tires (radials are a different animal) require constant care to minimize variables. Maintaining the desired size and air pressure is an art. With a little care and a repeatable routine, tire sizes can be managed preventing erratic growth changes. Prevention and a dedicated tire specialist is often the team component that keeps your car in the front. Maintaining a consistent approach to tire preparation is what allows you to land on all fours regardless of track conditions.

The goal is to keep the tires the tires sized properly avoiding unpredictable growth. Variables can be controlled or at least reduced. Starting with tires that are manufactured to the desired size is a best practice. Attempting to change a tire size by artificially stretching it with added air pressure is a sure way to produce false sizing numbers that change at the first heat cycle. A good racecar goes to junk if stagger changes in an unpredictable fashion.

Using a tire roller helps to measure stagger (roll out) quickly making quick work out of your tire stack adjustments.

For bias ply tires my general rule of thumb is to use a maximum of 2 pounds of pressure to increase or decrease the size of the right size tires from my optimal pressure. Any pressure beyond 2 pounds, above or below, the ideal right side tire pressure changes the spring rate, camber temps, and tire foot print potentially reducing speed. For left side pressures, I might allow a 3 pound variance but since we tend to run such low pressures on the left side use caution to avoid crossing over the minimum pressure line. Buy the tires at the right size. Spend the time to remount tires that are the correct size.

A 1/4" Stagger tape, used with a tire roller, gives you price readings. Be sure that your tape remains exactly straight and true on the tire.

There is debate on how much bias ply pressure variance you can utilize to get to your optimal stagger. For this article we are focusing on bias ply – it is well known the radial tires are extremely sensitive to pressure changes and even quarter pound pressure adjustments can be dramatic with radials.

Dave Juarez, the tire specialist at Gene Price Motorsports for the #26 Greg Pursley driven K&N Pro Series West team says, “with bias ply I can get away with 3 to 5 pounds of added pressure without adverse affect. For qualifying, 5 added pounds frees up the car and helps to build heat quickly”.

Growing tires is a bit of a myth. Sure, you can change the size with more pressure but making a tire bigger by stretching it only gains a small amount and that growth is often inconsistent. Dave Juarez says, “filling a tire to 50 PSI and letting it sit in the hot sun can make it stretch. Generally, a heat cycle is needed to keep the tire at the desired size”.

A common mistake I have seen with bias ply tires is that teams over fill tires to “stretch” them in an effort to grow the tires to get more stagger. These teams overfill the tires and then quickly drain the air down to race or practice pressure and take a measurement. This method always ends up with false size readings. As soon as the tire heats up, the artificial “stretched” reading disappears and the tire shrinks back to near its original size. You might grow the tire a fractional amount but if you were counting on the extra stagger to get through the center you can be assured that the tire size will change at race temperature.

2 pounds of variance is okay to get stagger, 2 more PSI in the rights and 2 less PSI in the works fine but any more pressure change than that and you are fighting evil with evil.

I have seen all kinds of tricks to change tire sizes. Over filling tires and bouncing them like a basketball to gain size. I have seen teams run too much air pressure in practice to help grow tires with a heat cycle – go too far and you risk cooking cooks the tire center. I have seen teams try to shrink left side draining them of air after a heat cycle and then dousing them with cold water. This method can harden the tire and rarely has much sizing benefit. It is tough to change once a tire is manufactured. Adding pressure or dropping pressure will get you a size change but really the size is determined at the time of manufacture.

Juarez says, “I have bounced tires also but it is a desperate last resort. You might be stretching the center of the tire but I wonder what is happening to the contact patch? It is hard to stretch a tire at the side walls. I still think you get what you get and after one or two heat cycles just count on tires being about that you originally measured. I have had tires stretch or even shrink during a race but it is out of your control. Just be very consistent with the way you prep your tires and you get a pretty good feel for what they are going to do”.

Dave Juarez states, “if you get a heat cycle on a tire and quickly drain the hot air and replace it with cold nitrogen the second the car comes off the track you can make the tire a little smaller or at least keep it from growing more”. Dave continues, “Adding nitrogen to a hot tire can help it to grow but not all that much”.

I never had any luck stretching tires on my Saturday night racing. I like to put 30 psi in the lefts and 50 in the rights and leave them for 30 minutes to let them get a set when they are new. After you put a heat cycle in them you get what you get. You can make them bigger or smaller with air pressure but you need the right size tire with the right pressure to be fast”.

Using nitrogen instead of compressed air helps with consistency. Nitrogen is nearly moisture free and air from a compressor contains moisture. You get moisture in the actual air but you can also get a lot of vapor from the compressor tank and lines. Moisture inside the tires creates added heat expansion and if any tire contains more moisture than the others in the set then stagger changes unpredictably.

Purging air out of your tires and replacing it with nitrogen will remove moisture resulting in consistent stagger throughout the race. This purge tool has a slide collar to "dump" air quickly through fast flow ports that can be used when your tire specialist is attending to the tire. The collar slides to the closed position and a bleed valve prevents air and unwanted atmospheric moisture filled air from re-entering the tire during the purging process allowing your specialist to work on many tires at once. Top teams use multiple purge tools. The purge tool clips on the Schrader valve and automatically adjusts your tire to nearly any pressure allowing your crew to multitask with confidence.

Nitrogen works well. Top teams have used Argon in their tires to further reduce moisture content. Argon and medical grade nitrogen produce such a small moisture reduction benefit that it is not worth the added cost. Dave Juarez states, “I have tried Argon and some other types of Nitrogen. Medical Grade Nitrogen was believed to be the preferred type but I did some research and found out that the only reason it is classified as “Medical” is the way in which the tanks are cleaned and filled. The chemical make-up is the same so there is no advantage within the tire”. Basically, Dave thinks standard nitrogen is a good economical choice.

Clipping on a purge tool to several tires allows tire specialists to replace moisture filled air with clean and moisture free nitrogen in record time. This purge tool clips on and can be set to very low PSI, preventing atmospheric pressure from re-entering the tire. The clip-on feature allows the tire specialist to set race pressures by adjusting the bleed valve, from very low, to maximum race pressures. Top teams have several purge tools clipped onto multiple sets of tires. On hot days, the clip on feature, allows teams to automatically bleed off pressure created by heat build up from the sun.

,Keeping water out of the tire during the mounting process is a big deal. If you are not careful you can get a bunch of mounting soap and water in one tire and half as much in another. Using WD 40 for mounting tires prevents moisture. WD stands for water displacement. The WD 40 lube is slippery enough to mount the tire and you can keep the tire sized right by avoiding using water all together”.

I have seen all kinds of devices that claim to eliminate moisture in tires. The goal is to maintain consistent growth. The practical goal is to have the tires grow in concert with each other so that set size is predictable. I once had a guy that wanted me to build and market a $60,000.00 dollar vacuum chamber to pull the moisture from each tire. The reality is that there is moisture in the tire rubber. The moisture inside the rubber is part of the manufacturing process and is a needed element for tire performance. Taking care of your tires is good but a $60,000.00 vacuum chamber gains you about zero in performance yet costs you a ton. I wish I was joking but there are folks that think a $60,000.00 dollar machine would be a good deal for short track racers. I am embarrassed to even admit I know about such a machine.

Using a top quality pressure gauge fine tunes your stagger with optimal pressure. This gauge comes complete with an angled chrome chuck and a ball chuck ensuring it works in every application. You always have the right gauge and can avoid worrying about being committed to one style of chuck. Racers can change out the chuck in thirty seconds as, for this gauge, the chuck threads on so teams can change as needed.

Juarez says, “I have used air dryers, desiccant moisture removers, clean nitrogen and so on but the most benefit is gained by having a consistent plan”. Depending on conditions, I purge the tires with nitrogen a minimum of 2 times but generally would prefer to use a humidity gauge and purge the tires as dry as possible. Usually it is 4-5 purges that are needed to purge down to a “zero” state – well near zero”. Dave continues, “If I am mounting the tire, I use the least amount of tire “soap” or mounting medium. When I seat the bead I use compressed air that goes through a dryer first”. Dave goes on, “you can create some stagger starting your right side air pressures slightly higher than “recommended” during your initial practice run on stickers but only if scuffs are allowed by your series on pit stops. When you run slightly higher right side pressures, the heat cycle in the tire will “hold” a bit more stagger.

Personally (Jeff Butcher), my goal in managing tires is to work with the tires and not against them. For short track cars and sticker tires I always put 20 PSI in the lefts and 30 PSI in the rights – I made sure the guys at the tire truck didn’t over inflate them from my numbers as I wanted the tires to be in their natural state every week without crazy air pressures that produced variables. In my experience, consistency allowed for predictability. Artificially growing tires was a sure way to have the stagger change during race conditions. I did make sure water was kept out of the tires and I used standard nitrogen, medical grade simply was a cost item that didn’t equal the value. I purged the tires 2 times as that seemed to be the point where the most benefit was gained. Purging more than 2 times gained a little but it takes time and our hauler had a limit on how many heavy nitrogen bottles it could carry. We had a nitrogen sponsor but 2 times seemed to remove most of the moisture. Consistently purging 2 times each week was a “routine”.

I think the mistake that is made by many teams is that cold measurements, taken after stretching “tricks”, create dramatic size changes that disappear during/after a heat cycle. The tires are what they are based on how they were manufactured and to think you can stretch the sidewall seems like a “mental stretch” to me. Really, you would have to break down the side wall cords to grow a tire so in my view, high using high air pressures with the goal of making a tire bigger simply ballooned out the center of the tire for a short while and any stretch is a mirage.

Matching sets, especially when you have multiple new sets, is part of the art performed a tire specialist. Dave Juarez states, “In a perfect world, the left sides would all be the same and the “average” would come from the right side tires”. Dave continues, “I try to match sets so you could switch left sides to add or deduct stagger on pit stops. I tend to lean toward using my Right Side tires to add or subtract stagger since the Right Side Tires take most of the load during a race. Most often, the 2-tire stop is right sides so having the option to switch tires around coupled with adding/removing air pressure is critical to handling and performance after a stop”.

Dave thinks, “Most of the pressures and tire sizing depends on your application or set-up. Most drivers can’t tell the difference in 1/8” of static stagger. During a run when the air pressure builds, the associated stagger change and air increase will have the greatest effect on handling. Pay closest attention to your “set” choices based on the set-up and handling of the car. If the Crew Chief and Driver are on the same page, it is far easier to “follow” and “manage” your available set options which is a big help in selecting sets for the race and qualifying. Nowadays, it is more important to keep your “brand” or serial numbers as close together as possible so your tire inventory comes out of the same batch creating added consistency.

Communication between the driver and crew is important and using different tire sizes to dial in the car can get you to the front. A well chosen stagger change can be huge. Making sure you know what tire sizes are on the car at all times helps you select the best set of rights or lefts.

Dave Juarez, “I like to use a tire roller and I trust a tape measure more for precision. I will measure along the tire shoulder when the tire is on the ground when needed and easily get accurate and repeatable results. I also need a stagger tool as in our series we are not allowed to jack up the car post qualifying”.

A billet CNC machined tire caliper gets you an accurate tire size readings quickly without the need to jack up the car. Many race series impound the car after qualifying making a precision tire caliper invaluable.

I like a tape measure because it is a little more accurate. Adding a tire roller just makes the measuring process so much easier. Being consistent and using a quality tire pressure gauge improves speed. Take tons of notes on your tire sets, and keep the inside of every tire as dry as possible. Experience is invaluable and the more knowledge you can gain the faster your team will run. Tires are everything so have a tire specialist on your team that is detailed and thorough

A quality tire specialist helps any team win. Tire experts are the hardest working people in the pits and need to react precisely to split-second decisions made by demanding crew chiefs. Top Cup Crew Chief, Shane Wilson, relies on Robert Osaki, flying him around the country for special events. Robert is well known for being the nicest person on the planet and is regarded as one of the best tire specialists in the business. Here, he is shown helping Gene Price Motorsports get their rubber to the road at Infineon Raceway in California.

Tires are a big investment for any team and a good tire guy is invaluable. Just think about the last pit stop on a big TV race and how the tire guy can mess up the fastest car on the track by handing the tire changer the wrong size tire or one with incorrect air pressure? Managing and massaging tires is an art. Robert Osaki, is known as one of the best tire guys in the business. Top teams such as Gene Price Motorsports and Kevin Harvick Industries fly Rob around the country, at great expense, because they can trust that he knows his tire stack inside and out. Rob’s knowledge, care and experience make him an asset to any team. To win races, your team needs a tire specialist that treats each tire like family. Find a cat like Robert Osaki and your car will always go on all fours.

Go Forward – Move Ahead
Jeff Butcher
7/1/11

Power Steering

Before racing power steering, caster was utilized to help cars turn left. Manual steering provided great feel but required Popeye forearms to get through the corners. Many drivers of today might fall out of the seat if it were not for the utilization of advanced power steering systems. It is clear that many drivers have extended their careers due to the power assist.

Serpentine belt drive power steering pumps are more durable. Today's advanced power steering systems are a giant leap forward compared to designs of the past. These advanced systems increase horsepower by utilizing smaller light weight pulleys and lighter belts. Serpentine belts eliminate slippage that can occur in V-Belt systems. New advanced power steering packages maximize flow and are more efficient resulting in marked improvements on the horsepower dyno sheet.

 Through technological advances, driver feel is optimized by advanced power steering systems and caster is now used as a chassis tuning tool. Steering effort relies on the precision built into the power steering system independent of chassis and caster settings.

Power steering pumps, and components, are precision instruments that are built with the latest manufacturing technology. Close tolerances are a requirement for power steering systems to perform. To sort through the intricate details, and variety of power steering application options, we sought out racing power steering experts CJ Jones of Jones Racing Products and Michael Deppa of KRC Power Steering. Both companies utilize advanced power steering systems. The differing philosophies of these manufacturers offer racers a variety of successful power steering package choices.

What are the recent advancements made relating to racing power steering systems?

Michael Deppa:
Coil bind set ups, wide soft compound tires, high amounts of caster and fast steering boxes place more demand on the power steering system. Faster racks, small ratio steering boxes or quicker steering boxes often require more volume feeding the servo. Aggressive front end geometry and high banked tracks can place high amounts of load on the wheels. Faster rack-and-pinions require more volume to fill the slave cylinder due to the quicker cylinder stroke. Manufacturing advancements allow for managed pressure relief settings, in the pump, even at the high pressure.

Pavement late models, on semi-banked tracks, often create around 600 PSI of pressure in the middle of the corner, while Modifieds at Bristol create 1500 PSI – Dirt cars can see the same 1500 PSI. Hardware has changed to meet the new pressure challenges and changeable flow valves allow pump volume to be adjusted throughout a large range for precision tuning in varying applications.

CJ Jones:
Through research and testing, our team discovered that power steering pump performance relied on building systems with a solid foundation which allows the pump’s internals to provide excellent fluid control, pressure and flow curves along a wide RPM range. . Machined CNC Aluminum construction, manufactured with exacting tolerances, provides the rigid platform required for the best performance. A solid foundation allows the internal pump components, and flow controls, to provide optimal fluid management and pressure stability. Fluid flow curves, throughout the RPM range, can be specifically tailored due to the rigidity engineered into the CNC machined housing.

Our extensive testing illustrated that matching pumps with integrated fluid reservoirs created optional solutions for the racing market. An integrated fluid reservoir simplifies installation and is more cost effective. Removing the remote tank eliminates four fittings and two hoses. Overall system performance is enhanced, and restriction is reduced, due to the elimination of unnecessary hoses and fittings. Integration ensures fluid feed, at the source, providing advantages as compared to remote reservoir designs. The performance of the entire system is enhanced; there is never a possibility of the pump struggling to get fluid from the remote tank source.

An integrated reservoir tank eliminates hoses and fittings increasing flow characteristics. With the tank mounted right at the pump fluid is ready available to feed the pump reducing cavitation.

Explain your thoughts on power steering fluid.

CJ Jones:
We tested all the available fluids and our group felt improvements could be made by producing a synthetic fluid designed for the racing market. Synthetic handles extreme temperatures nicely resulting in steering consistency throughout the fluid temperature range. A confident steering feel, from race start to finish, is obtained due to the performance of our proprietary synthetic fluid. Foam free and crystal clear synthetic fluid eliminates cavitation during full operating temperature even on long green flag runs.

Clear power steering fluid helps the team to keep a watchful eye on the stability of the system with just a quick glance at the fluid itself. Racers are able to spot any type of contamination in the fluid, helping to catch any problems with the rack, steering box or hoses. Catching one of these problems will protect the rest of the system.

Weekly fluid inspection should be standard practice and a complete flush and fluid change is recommended 2 to 3 times a year. If you run more than once a week, or often run in long events, then increasing the fluid change schedule is recommended. Racers should adapt their schedule based on their usage but 1500 to 2000 laps is a reasonable guide for synthetic fluid replacement based on a standard weekly Saturday night type schedule. Contaminated, debris filled or burnt fluid should be replaced immediately.

Whether you choose a full synthetic fluid or a petroleum based fluid, utilizing clear fluid provides the opportunity for system checks with a quick glance. Clear fluid that is discolored gives teams a heads up in identifying potential problems in the power steering system. Hose issues or other problems are quickly resolved when clear fluid suddenly becomes discolored. Purchasing small bottles for top offs and large bottles for full system fills ensures efficient use of your fluid.

 Michael Deppa:
We like petroleum based fluid as it is incompressible and safe for internal system components. Low viscosity petroleum based fluids flow through the passages of the pump with a constant density through pressure change. Petroleum based fluids cool nicely and are readily available. Fluid issues, such as boiling, give racers an opportunity to inspect the entire system. Corrections can be made right at the problem source that is creating the fluid boiling point.

Pavement cars sealed off tighter for aerodynamic purposes may benefit from a cooler. Lower fluid temperatures provide fluid integrity but generally a cooler is not mandatory. If a cooler is used, the best place to mount a cooler is in front of the radiator so the ducting forces the clean cool air through the cooler.

We recommend the fluid be changed roughly two to three times a year in most racing applications, but it should be changed immediately, along with a thorough flush, if the fluid is discolored or smells burnt. It also should be changed more often if you race more than once a week on a regular basis. Before every race we recommend checking the power steering fluid level. Using clear fluid as a diagnostic tool makes it simple to spot problems and discoloration.

Other weekly maintenance includes checking your belts and pulleys for wear, checking belt tension, clearing pulleys of debris, and inspecting your hoses and fittings for any leaks.

How do you determine pulley sizes for power steering systems?

Michael Deppa:
For racing applications you should ensure you do not over spin pumps at RPM levels above the pump rating. Special caution should be utilized with an OEM pump to avoid excessive RPM. Manufacturing pumps, specifically for racing, allows for increased RPM’s in the 9000 range.

To determine the correct power steering pump pulley size, you should consider that most constant flow vane-style power steering pumps achieve maximum flow rate at 1500 RPM at the pump. A well designed pump will flow at a constant rate from 1500 RPM of pump speed on up. Over spinning the pump will not increase the flow rate of the pump. We recommend turning our pumps, on most engine set-ups, at around 4,000 to 5,000 RPM of pump speed. In some instances, such as dry-sump mounted pumps, the pump may not be spinning fast enough at low engine RPMs to get maximum flow out of the pump. This may cause the steering to feel tight in the pits. The key is to make sure the best feel is found at race speeds. Racers can go online for the pulley RPM formula or consult or techs for specific information to ensure all variables are taken into account.

CJ Jones:
We recommend that racers identify power steering, pulleys and mounting hardware based on the engine RPM range and the accessories on their car. Power steering pulley size is used to fine tune the pump speed for optimal pressure and flow curves. Ensuring a cool running pump, that is mounted properly, is obtained by utilizing the vast array of configurations available. A call to our techs can help teams to achieve the best system for their application. Equal effort can be placed in improving existing systems for maximum performance even if a team is enhancing their existing system verses starting from scratch. Regardless of the scenario, expert tech support can make dramatic improvements in power steering performance.

Why are serpentine belt systems better?

Michael Deppa:
Serpentine belts are capable of withstanding higher RPM’s without the belt stretch that can be seen with V-Belt systems. V-belt stretch causes slippage and rapid pulley wear. The Serpentine belt structure requires less material, thus the belt itself is lighter. Serpentine belts provide greater grip to the pulley allowing smaller pulleys to be used. Pulleys can be made in smaller diameters reducing rotating weight adding horsepower and acceleration. With appropriate tension, Serpentine belts last longer and coupled with smaller pulleys the long term cost savings are significant.

CJ Jones:
We searched for alternatives to V-belts over 30 years ago and found serpentine systems improved the drive of accessories at optimal RPM. Serpentine pulleys offer multiple light weight ratios that are more reliable at the high RPM found in racing. The variety of pulley options reduces belt induced horsepower loss. The serpentine concept increases reliability and is a superior alternative to V-Belt designs. Serpentine reliability and longevity are a dramatic improvement over V-Belt systems.

How do you determine the correct pump for a given application?

Michael Deppa:
A major consideration is identifying how the pump is to be mounted. Will the belt drive be on the front of the engine or off the bell-housing? Will the power steering pump drive off the dry sump pump or cam shaft? Once the pump is mounted, the last step is to fine tune the pumps flow rate to the application. Standard flow rates work in a majority of applications but differences in rack-and-pinions, steering boxes or steering gears may require simple flow valve changes to optimize the flow rate to the steering system. 1600psi of pressure relief is the highest safe rating we recommend. We can adjust the relief valve from 1000-1600psi. Other considerations relate to the tank – will it be pump mounted or remotely mounted?

Power Steering Pump manufacturers have developed a variety of mounting options to suit nearly any application. Consulting your power steering company of choice will provide you with many problem solving mounting options.

Explain the advantages of a pump designed for racing as compared to past or stock designs?

Michael Deppa:
GM Saginaw pumps are built for mass production with low cost at the major factor.

Designing a racing pump from the ground up allowed for input from industry expert Tony Woodward. The evolution of pumps specifically designed for racing allows for the use of superior materials and very tight tolerances. Diameters can be held to tolerances of 1 micron. Honing and hard coat processes create longer lasting better performing pumps that go beyond the technical abilities of a stock Saginaw style pump. Improved manufacturing processes provide greater power assist when you need it. Efficiency improvements result in temperature drops of 30 degrees or more illustrating the advances of modern technology.

A power steering pump designed specifically for racing applications reduces fluid temperatures and increases performance resulting in a smooth steering package.

What other power steering system knowledge would you like to pass on to readers?

Michael Deppa:
Most steering issues we come across on a daily basis are due to plumbing issues. The feed line for remote systems should be no longer than three feet and should be a hose designed specifically for power steering with the correct vacuum rating. Push-lock and braided-stainless hose will not work for a power steering system. Once hot, if oil is pumped through these non rated lines, they can soften and will more easily be sucked shut, starving the pump of fluid.

Remote tanks should be mounted above the pump and care should be taken to ensure the line is insulated from header heat. If the line is routed below the pump, and then enters the pump from above, it can create air pockets in the line creating steering with hard spots and inconsistency.

We check the fluid level with the engine off. Care should be used to prime and bleed the air from the system. Primed and bled properly - the fluid level should not change once the engine is turned on, unless there is a leak in the system. The fluid level should be well above the return line where it enters the side of the tank. If the fluid level is not above the return port, excessive fluid aeration will lead to cavitation.

CJ Jones:
Dyno testing each power steering pump, to verify and document flow and pressure characteristics, improves on track performance allowing for specific tuning for individual drivers. Dyno testing is something we feel very strongly about and we believe every pump should be run on a specialized pump dyno. Continual improvement processes are enhanced through the rigorous daily dyno testing.

Serialization allows baseline numbers to be matched so that Saturday night short track racers, or Super Speedway Cup stars, can maintain the steering feel that is best for their situation utilizing years of technical support experience. Storing documentation allows drivers to repeat the feel desired from the steering system for future needs.

Serializing pumps allows for storage of information that can be pulled up for baseline comparison at anytime.

Jeff Butcher:
Utilizing the correct steering wheel size will help your driver to be fresh at the end. Larger diameters reduce back pain and find the correct "feel" is very driver specific. One driver likes the slightly slower and smoother performance of a large wheel and other drivers like the quick reactions of a small wheel. Small wheels can make it more difficult for drivers to be smooth. Working to find the optimal size for each driver is another tool that can make your stopwatch produce smaller numbers.

Using a top quality steering wheel gives the driver maximum feel and feedback. Quality steering wheels are round where as knock off wheels can be oblong creating an erratic feel. Mounting your steering wheel as close to your chest as possible reduces back strain. The best steering pad available should be a must have item for any team.

Quality power steering systems provide excellent feel and keep drivers up on the wheel for the entire race – there is no need to “ride” to conserve driver energy. Running hard every lap is possible due to the design of a good steering system. To maximize feel, your steering shaft should be mounted solidly with the steering wheel located in a comfortable position.

A rigid steering column mounting system gives your driver reliable and consistent steering feedback. Steering columns that flex or have bent steering shafts create unpredictable steering motions. Using the proper mounting hardware is an easy way to ensure your advanced power steering components are fully utilized.

Mounting the wheel as close to the chest as is reasonable allows more leverage to be applied to the steering system and back strain is reduced. Proper positioning gives the driver more power in the turns they can stay in the seat for the entire race. A racing steering wheel should be paired with a precision machined steering wheel quick disconnect. Close tolerance splines connect the driver to the wheels for ultimate control while providing the safety of a quick release system..

Steering wheel disconnects are a must have safety item. Tight splines transfer feel from the tires directly to your driver for enhanced feel. There are many quick disconnects to chose from and this is an area where the old saying "you get what you pay for" applies.


Each track, car type and driver style presents many variables. Today’s power steering system manufacturers have the resources to offer the correct hardware to maximize the potential of nearly any car. Smooth and dependable steering feel, with proper power assist, promotes better feedback to help drivers dial in set ups. Drivers can utilize the power assist to go the distance better than ever before and taking the time to work with your power steering supplier will help your team to easily turn into victory lane.

Go Forward – Move Ahead
Jeff Butcher

6/1/11

Organizationally Challenged

Fast and Furious at the movie theater is much more fun than acting out the Dukes of Hazard at the track. Enjoying a good movie with popcorn and a soda is fun – disorganization at the track leads to insanity and the increased pressure paints a landscape colored with rash decisions. Advanced technology and the variety of adjustment options, increase the difficulty of recording set up information and track side changes. Speed will be created through pre-planning and organization – Chaos not required.


Good decisions can be made when the air in the pit area is calm and an orchestra of advanced planning moves your crew in perfect harmony. A well guided crew, given the proper organizational tools, will lead you to the winners circle by following a pre-rehearsed program where each team member performs based on a plan that is implemented with precision.

Staying organized is accomplished through prior planning. Slowing down to go faster is the recommended path and investing the time to build documentation as you go will allow you to quickly pull data for future use. All chassis adjustments have value whether they make the car faster or not. The key is to document information in a displayable fashion with reliable people taking detailed notes every step of the way.

A coordinated organizational plan, born in the shop, sets in motion a productive route that gets your race week started on the right path. Detailing the shop set up gives you a baseline to chart changes made during the hectic pace that is inevitable at the track. Being prepared, in advance, gets you through Tech Inspection and out running laps allowing your team to take full advantage of every practice session.

In the shop, a Chassis Prep Checklist ensures that all projects are complete and all bolts are tight. Maintenance items can be checked off one by one so the entire team can visually see what is complete and the group can focus on the remaining items to be completely ready the second you get to the racetrack.

Ray Evernham lived by the mantra that "Luck is when Preparation meets Opportunity". After winning the Brickyard, Ray sent me a brick with the important quote engraved into the brick. The gift was a thank you for being a tiny cog in their championship effort. Ray took the time to thank all that helped their team win and the quotation, etched permanently in red brick, is a daily reminder for me to be prepared on and off the track.

For all of my race teams I invoked a shop rule that stated, “If you bolt it on you tighten it up in race ready condition – every time”. Many times crew members simply hang a part on the car and leave it loose because they plan to take it back off or do other work – even then, I require all parts to be wrench tight. It is too easy to forget and too often parts fall off of cars because someone just hung a part in place instead of taking 5 seconds to use a wrench. It takes little time to tighten up race parts – it takes a ton of time to repair damage after parts fall off. Losing a race due to poor shop practices is easily avoidable.

I know the cars I worked on finished every lap because they were always ready to go. I also know that when I was a hired gun, helping other teams, it seemed there was something loose on the car all too often. If you hang it – tighten it. Make tightening parts a hard and fast rule on your team and you will “save” time and save money. A Chassis Prep Sheet will assist in making sure all items are complete and race ready. It pays to place a reliable person “in charge” of the Chassis Prep Sheet.

Keeping detailed notes at the shop and at the track will help your team to be ready right out of the box. Detailing all changes, even changes that don't work out, will help your team to build their knowledge base producing more valuable use of practice time.

After your car is race ready then bolting in your winning set up is the next priority. A Chassis Set Up Sheet will give you a central location to make notations in the shop that allow you to repeat winning set ups in the future. Done correctly, documenting your set up fully in the shop displays the information for quick review. An organized Chassis Set Up Sheet builds the foundation to grow documentation based on needed track side changes.

Often, in our attempt to find elusive speed, the changes made at the track make the car go slower and sometimes harder to drive – even then it is crucial that changes are documented fully. Over time, the so called adjustment mistakes will clearly display a pattern that allows you and your team to increase your learning curve. Information is always good even when the documentation records negative results.

Be sure to assign a very responsible crew member that you can count on to make notations each time the car hits the track. When a chassis change results in a dramatic improvement it pays to make extensive notes and “flag” such set up victories for quick future reference. Filing your Chassis Set Up Sheets is key as well and it is a giant time saver to have a database of information on file to help prepare your car for a return visit to the same track.

Utilizing a Timing Sheet will provide session lap times that can be quickly reviewed. Often, a car might be blazing fast on lap 1, 2 and 3 but then fall of at the end of a practice session. A short run set up might be great for qualifying and notes will help you to decide. By recording your lap times during each and every session your team can find patterns allowing for discussion and proper decision making. Your Timing Sheet can be stapled to your Chassis Set Up Sheet at the end of a run so you can analyze the changes made and couple the set up information with real time speed information.

In addition to lap times, tire temperature information will allow your team to fill the set up informational database with a complete package of repeatable documentation. Tire Temp Sheets expand your information package - viewed in conjunction with your Chassis Set Up Sheet and your Lap Time Sheets gives your team planning tools to consistently find more speed. Once found, your speed secrets should be written down each and every time in a common format that allows for a sustainable documentation process.

Tire Sheets and accurate tire temps are one of the few "Crystal balls" found in racing. A balanced set up can be obtained by tracking tire temps and making adjustments to find the set up that utilizes all four tires to their maximum capability.

Quality documentation provides a focused format resulting in team discussions that are based on history, facts and real world experience. Writing down your set ups and track side changes, with support of Timing Sheets and Tire Sheets, saves time. The small investment in time for documentation is more efficient in the long run. Creating documentation in real time and “as you go” is the only way. Trying to re-create documentation at a later date leads to errors as our memories fail and important details are forever lost. Slow down to go fast and cultivate the discipline to “construct” your documentation as you go. Waiting until later makes the documentation process a chore – doing it now becomes a good habit that is a required element that fits naturally into your regime allowing for sustainable positive action.

Driver feedback should always be recorded and be a vital component of your documentation process. Make driver feedback notations and record the changes made to the car before it goes out on the track for the next practice session. Staple together your Chassis Set Up Sheet, Timing Sheet and Tire Sheet from each session and you will have instant access to vital information when you need it most.

Over time, your library of available recorded information will become the go to resource and you will establish your own baselines and rule sets. When an “ah ha” moment occurs due to a successful adjustment, be sure to flag those sheets and spend extra time documenting driver feedback. You never know what the future holds and a successful fix to a chassis handling problem today may apply to another track or circumstance. The best documentation evolves with your team and becomes a pivotal tool that participates in the ongoing growth of your orchestrated racing program.

Go Forward – Move Ahead
Jeff Butcher
5/1/11

Master Cylinder Math Explained

Going faster creates a need for stopping faster. Efficient braking is based on choosing the right components and matching the proper combinations will result in a brake system that works in conjunction with the specifics of your car, track and driver style. It is highly recommended that you work with your brake company engineer to assist you in building the right combination to tailor a system for your application. Since pad compound, rotors, calipers and master cylinders all work together in relation to car weight, speed and track characteristics, it makes sense to think of your brake system as a package. Each brake component relates to the other braking variables and an individual change may necessitate the need to reanalyze your entire brake system in your effort to achieve a balanced clamping force on your car.

A Billet Clamp On Reservoir Mount allows you to mount your brake fluid reservoir at a high point resulting in improved brake bleeding. Remote mounting keeps unwanted heat away from your brake fluid.

We contacted long time brake expert Carl Bush from Wilwood engineering to help our readers understand the brake system. While I encourage you to consult your brake company engineer to build the right braking system, I also encourage you to learn how the parts interrelate. With your own knowledge base, education will allow you to better communicate your needs resulting in the best brake system possible.

How do you pick the proper master cylinder?

Carl Bush:
Master cylinders are an integral component in the brake system. They are responsible for sending the correct amount of pressure and balance to the brake calipers. But it must be remembered that they are only one component in a system, and do not function alone. Brake requirements for different types of race cars will vary by component and element. But all systems do carry a common thread. They must allow the driver to stop the car with comfortable leg effort while contributing to the overall handling and performance of the car.

How do master cylinders work?

Carl Bush:
A master cylinder is used to convert force from the brake pedal into the hydraulic pressure that operates the brake calipers. The amount of pressure generated is a function of the force being applied, divided by the master cylinder bore area. A 1” master cylinder has a bore area of .785” inches squared. For every hundred pounds of force applied to the master cylinder piston by the pedal pushrod or balance bar, that master cylinder will generate pressure equal to 100 divided by .785 or 127.4 PSI. By calculating the area in inches squared (bore x bore x .785”) for any master cylinder size, you can calculate how much pressure change would be affected by a bore size change.

A 7/8” bore master cylinder has a bore area of .6” inches squared. If we apply that same 100 pounds of force to the 7/8” master cylinder, using the formula 100 divided by .6, that same 100 pounds of force from the pedal will generate 166.7 PSI. A decrease in master cylinder bore area produced a proportionate increase in line pressure. This line pressure management becomes a key factor in setting brake balance.

Master Cylinder bore size is the element that affects pressure.

Jeff Butcher:
So Carl provides some great information about how master cylinder size works with your leg effort and brake system. How can we use Carl’s master cylinder bore area math to our benefit? Since my articles try to remove some of the engineering speak and present information into layman terms, I will try to expand on the math that Carl is illustrating. If you read all the way through you will see that the math is easy once you get a handle on all of the terminology. By understanding the basics you will have more data to make informed decisions.

Carl explains that a 1” Master Cylinder has a bore area of .785” squared. To get to this number you use the formula for Area which is: Area = 3.14 (Pi) multiplied by the radius squared. So you calculate the radius of 1” bore which is simply half of the diameter which equals .5” (half an inch). The result is that a 1” master cylinder has a radius of half an inch. You then multiply your radius which is a half an inch (.5) by itself so .5” X .5” = .25” or a quarter of an inch. .Multiply .25 X 3.14 (pi) and you arrive at Carl’s .785” area number. Basically, I just repeated what Carl said in an effort to make the math more simple and I bet the barrage of numbers made the calculation more intimidating and confusing? It’s ok – we will get to a simple way to look at the master cylinder math and going through the steps will make the process easier to understand.

Another way to explain Carl’s math uses a 7/8” master cylinder as the example. We will do the calculation and show our work to reinforce the math for calculating bore area.

Bore = 7/8”

7 divided by 8 gets us the decimal equivalent = .875”

The Radius is .875” divided by 2 = .4375”

.4375” Multiplied by .4375” (Squared) = .1914”

.1914” Multiplied by (Pi) 3.14” = .6” - which is the answer Carl explained above.

With the progression towards understanding the math we can do take the steps the easy way. Use Carl’s magic formula of Bore X Bore X .785” (.785 is the magic number that simplifies the above equations as it simply pre-calculates the squared business relating to Pi in advance). So a 7/8” bore is .875” X .875” X .785” = .6” Bore Area. It turns out you can use the number .785” and multiply it by ANY Bore X Bore as the reusable number of.785” is a derivative of Pi and it is a repeatable math number that can be used with any and all bore sizes. So, the complicated math shown relating to Master Cylinder Bore Area can be simplified. Now we have taken another step towards understanding.

Bore X Bore X .785” - you can always use .785” in the equation.

Let’s check with the Easy 1, 2, 3 method:

For an example 7/8” Bore master cylinder the Bore Area math is:

Step 1 – Convert the fraction Bore to a decimal by dividing the bottom number in the fraction into the top number.

7 divided by 8 = .875”. 7/8” is the bore marked on the outside of the master cylinder and .875” is the decimal bore equivalent of 7/8”

Step 2 – Multiply the bore diameter (our example is .875”) by itself which is the same as bore squared.

.875” X .875” = .766”

Step 3 – Multiply the bore squared result from step 2 (.766) by the reusable number (always .785 with every master cylinder size – you can count on .785 to work every time with every master cylinder size).

.875” X .875” = .766

.766 X .785” = .6

.6 is the Bore Area for a 7/8” Master Cylinder!

The EASY 1, 2, 3 Bore Area calculation is right here!

Our example was for a 7/8” master cylinder. Now you can use the bore size on your car and substitute your actual numbers to come up with your Bore Area, front and rear, by following the 1,2,3 calculation above. Now that we have our Bore area numbers of .6 for a 7/8” master cylinder and .785” for a 1” master cylinder what do we do next? Carl states that a smaller master cylinder bore creates more pressure with an equal amount of force. A 1” master cylinder creates 127.4 PSI as compared to a 7/8” master cylinder which is 166.7 PSI based on your foot making 100 pounds of force at the master cylinder. It is important to consider that the smaller cylinder makes more pressure but the smaller bore will move less fluid. More travel will be needed to make up for the reduction in fluid moved by a 7/8” master cylinder as compared to the larger 1”. Carl explains further in the next section.

Utilizing a bolt on caliper mount ensures that your calipers are square to the rotor improving pad wear and braking efficientcy.

How do fluid volume and leverage come into play?

Carl Bush:
While a change in master cylinder bore size affects a pressure change, it also changes the amount of pedal travel realized to add the additional stroke needed to displace enough fluid to move the caliper pistons. This volume ratio plays an important role in the clamping capability of the caliper, and leverage that the driver has to generate that clamping force. The ratio between the caliper and master cylinder is a function of the net effective caliper piston bore area divided by the bore area of the master cylinder. To compare these ratios and do the calculation, you must start with the total piston area of the pistons in one side of one caliper.

A front brake set using four piston calipers with 1.75” diameters will have a net bore area of 4.8” inches squared as each 1.75” diameter piston has an individual bore area of 2.4” inches squared.

(Jeff’s Easy Math works for caliper piston bores too – 1.75” X 1.75” = 3.06” X Reusable Number .785” = 2.40” X 2 Pistons = Carl’s Net Bore Area of 4.8”)

Carl Bush-continued:

By running the formula, the leverage ratio between a 7/8” bore master cylinder and the 1.75” four piston caliper will be equal to:

Effective Caliper Piston Area (4.8) / Master Cylinder Bore Area (7/8 which is .6) =

4.8 / .6 = 8 for an 8:1 ratio.

The driver leverage is then determined by multiplying the Pedal Ratio x the Caliper Piston Bore to Master Cylinder ratio. (Note from Jeff: “The pedal ratio is marked on your pedal assembly when you buy it or use the Pedal Ratio Drawing shown”).

Carl’s Example:

Pedal Ratio (6:1) x (Piston Bore (4.8) / Master Cylinder Ratio (.6) results in (8) = Driver Leverage (48:1)

6 x (4.8 / .6) = 48:1

You can substitute any number of piston bore combinations with master cylinder sizes with any pedal ratio to determine the driver’s actual brake leverage.

For fun Carl has given you the answer to the test with this chart.
Common Caliper Piston Size Diameter / Area

Diameter, Inches 1.12 1.25 1.38 1.62 1.75 1.88 2.00 2.38 2.75 2.94

Area / Piston, Inches Sq .99 1.23 1.48 2.07 2.40 2.76 3.14 4.45 5.94 6.78


Common Master Cylinder Bore Sizes / Area

Diameter, Inches .62 .75 .81 .88 1.00 1.12

Area / Piston, Inches Sq .31 .44 .52 .60 .79 .99

By changing to a 7:1 ratio pedal (from the 6:1 shown in Carl’s Example), the driver would then realize a final ratio of 56:1 with the same caliper and master cylinder (Jeff’s math 7 x (4.8 / .6) = 56:1). Consequently, a 5:1 pedal would only give the driver a 30:1 ratio (Jeff’s math 5 x (4.8 / .6) = 30:1). If we compare the front leverage ratio to the rear leverage ratio on any given car, this tells us the front to rear static bias capability of the car.

Pedal Ratio is determined by dividing length "A" by lenght "B". The amount of force at "F" determines the force to the master cylinders.
Now that we know the math, can you explain a common set up for our readers?

Carl Bush:
A common set up that could be found on a weekly show short track asphalt car is to use the example above with 1.75” piston calipers on the front with a 7/8” bore master cylinder, and a pair of 1.38” piston calipers on the rear with a 1” master cylinder. A 6:1 floor mount pedal ratio is also common. We have already determined that the 1.75 pistons with a 7/8” master cylinder and a 6:1 pedal will give the driver an overall brake leverage of 48:1 on the front. If we use the same formulas with the 1 3/8” piston calipers and 1” master cylinder on the rear, that produces a total driver’s rear leverage ratio of 22.75:1. When we compare the 48:1 ratio in the front, to the 22.75:1 ratio in the rear, we see that the car will be baselined with a front to rear static leverage bias of 67.8%, as long as the balance bar is centered and equal force is being applied to both master cylinders. You can substitute any combination of parts and their sizes to determine the exact influence they will have on the baseline static bias ratio.

Four piston calipers can usually be found with piston sizes from 1.125" to 1.875". The area of two pistons on one side of the caliper determine the calipers influence on clamping capability.


How do we use pressure to determine brake bias?

Carl Bush:
Although racing with a perfectly centered balance bar is the ideal goal, it seldom happens in reality. Besides, one of the advantages in using an adjustable balance bar is having the ability to adjust that leverage to optimize handling and driver comfort on track. Trying to measure the post-race leverage split at the balance bar is difficult and unrealistic. However, using pressure gauges to measure pressure differentials s at any given balance bar setting is relatively simple. The brake gauges will show the actual pressure split in the car based on the balance bar adjustments made by the driver. Those pressures can then be multiplied by the effective caliper piston bore areas to calculate the last on-track static bias settings.

Calipers such as this metric replacement only have one piston on one side. The calculation of their clamping capability still uses the same formula.


Going back to our (common set up) example, if we apply 50 pounds of leg force against a 6:1 pedal, we will generate 300 total pounds of force against the balance bar. If the balance bar is perfectly centered, it will distribute that force equally to each master cylinder. With each master cylinder receiving an equal force amount of 150 pounds, the 7/8” master cylinder should produce 250 PSI (Jeff’s math: 250 PSI comes from 150 divided by .6 which is the 7/8” master cylinder math result) while the rear 1” master cylinder produces 192 PSI (Jeff’s math: 192 PSI comes from 150 divided by .785 which is the 1” master cylinder math result). In practical use of gauges, you can use any level of effort and pressure for your comparisons. The end result will be the same.

When the front pressure of 250 PSI from the 7/8” master cylinder is multiplied by the 4.8” inches of caliper bore area of the front 1.75” piston front calipers, we get a front clamping force of 1200. On the rear, we will have 192 PSI x 2.97” caliper area or 570 pounds of rear caliper clamping force. When comparing the these front to rear clamping force total in the same way you would compare wheel weights for balance, we would see that this car has a total of 1770 pounds of caliper clamping force at these line pressures with 1200 pounds or 67.8 % on the front. It’s that same static bias ratio that was measured using the overall driver leverage ratios.

Now, if every car and driver had the same braking requirements and pedal feel preferences, we would never need to adjust anything. But, every car and every driver are unique and adjustments will get made.

The ratio examples that have been used here are very common in many short track asphalt cars. But your car, for a wide variety of reasons, may have quite different requirements. As a racer or crew chief, you can use these formulas to map the existing brake set up on your own race car, and then make calculated decisions when the desired handling or driver feel isn’t being delivered. The inability to reach the desired bias or driver’s feel of the pedal is the indication you will need to evaluate your component selection and consider possible alternatives. By using the formulas in these examples, you can accurately calculate what affects a component change will make to your existing baseline, and record those final ratios in your records to use for future adjustments and set up for any given track type or conditions.

Jeff Butcher
As you can see, using the experience of you brake manufacturer is very valuable. Still, when you breakdown the math it is not all that hard. By understanding the pressures, bore areas and ratios you can improve your understanding of the brake system. A thorough understanding will help you to make improvements to an existing car or transfer learned knowledge to a new car. Be taking the time to understand the basic math behind the braking system you can calculate and record winning brake set ups. Slowing down to do the math will help you to go fast.

Go forward – Move Ahead.

Jeff Butcher
3/1/11