Three Link Lessons

Have you ever driven a fork lift or other hot rod that had the steer wheel in that back instead of the front? Rear steer rigs turn quickly and the term “push” just would never apply. Understanding your three link suspension can give you adjustment tools to help you roll through the center of the turn or help to hook you up on exit.

In general your static rear setting should be dead square. In your shop you need to spend the needed time to ensure that your rear end is exactly square. Once your rear end is square it helps to record the measurement from a brake rotor to the frame as well as from the trailing arm brackets to the frame both left and right. Keeping these measurements on hand will allow you to make track changes with the confidence that you are maintaining a square rear end setting.

All of my shop set ups include a rear end that is absolutely square. It is always my goal to maintain a square rear end and use all the other adjustments to find the right set up. I always feel that changing the square is a crutch that can create late race handling problems and potentially make your late race tires under perform.

Clamp on aluminum trailing arm brackets allow you to set the trailing arm angles to help your car turn through the center. You can arrange your three link set up for over steer or under steer through chassis roll. Experienced crew chiefs use the three link set up as part of their set up package.


While I try to avoid messing with the rear end square it is an amazingly effective adjustment. Drivers always provide instant feedback and a rear end square adjustment is felt instantly. If you have a car that is loose in that condition must be fixed. Drivers can adjust their line for a center push or exit loose but entry loose means you simply have to lift sooner.

If you toe in your trailing arms at the front you can use the J-Bar to help over steer the rear end to cure a push in the middle. In this example, mounting the frame side of the J-Bar higher than the pinion side moves the rear end housing to the left as the chassis rolls. As the housing moves left the RR trailing arm gets longer and the RR tire moves back helping the car to turn.

If I have exhausted my reasonable loose in adjustment ideas I might choose to shorten the RR trailing arm an 1/8” to help cure the loose in condition. Often moving the RR ahead cures the loose in condition but you run the risk that the fix is short term. It is possible that you could get a late race center push or the loose in condition could return after the tires heat up and wear a bit. Experience at a given track plays a big role here.

On some days it seems that the push in the center won’t go away. Again, I try to avoid messing with the rear end square and go through all of my other ideas before moving away from square. To place this concept in perspective I would say 95% of the races I have ever been around in involved a square rear end. I would say I got a nice handling improvement about half the time that I moved the rear end and saw some or little improvement the other half. Hey, sometimes you miss the set up and it is what it is.

If the car has a push in the center then I might shorten the LR trailing arm 1/8”. It would be rare that I would recommend going more than an 1/8” and really I will stick with the thought that square is best 95% of the time – maybe even 98%.

You can think out your rear link set up and by understanding how and when the car rolls you can use the trailing arms to help dial in your set up. When using trailing arm angles to help your set up it pays to truly understand the movements at each section of the corner as well as think about any drawbacks that rear steer or under steer might create.

To help the car turn through rear steer you can run the RR trailing arm uphill a ½”- 1” at the front. As the car rolls the RR trailing arm will push the rear end housing back on that side. The uphill RR trailing arm adds anti-squat to the car which helps forward bite under acceleration so I like to run some uphill angle in the RR trailing arm. Maybe a ½” up is a starting point.

To really add over steer at the rear end housing you can mount the front pivot point of the RR trailing arm towards the center of the car. With the trailing arms toed in at the front you can use the J-Bar mounting angle to help steer the rear end through roll. If you run the frame side of the J-bar is higher than the pinion side the rear end housing moves left through roll. As the housing moves left the RR trailing arm gets longer and pushes the RR tire back producing rear steer that will help the car turn.

If you want the rear end housing to under steer then mounting the RR trailing arm level and perpendicular to the rear end housing will produce the desired result. As the car rolls the RR Trailing are will shorten pulling the RR tire ahead.

When it comes to trailing arms I try to avoid linkage arrangements that go though center under roll. In other words – if the trailing arm starts on an uphill angle I do not want it to go past level and then head downhill. If the travel was enough to create a down hill angle under full roll I would make an adjustment as this can make the care unstable. I want to avoid having the RR tire to move back and avoid having the trailing arm travel through level which would cause the RR to begin moving forward.

Typically, I like run the LR trailing arm up hill about ¾” to 1”. There is much debate on this but I like to have a little anti-squat in the car to promote bite under acceleration. If you run a high amount of wedge then level may be a better idea. Since the left side is lifting in the corner the angle increases and the LR trailing arm shortens and keeps moving in the same direction. Again, when it comes to trailing arms I try to avoid linkage arrangements that go though center under roll as going through center can create an unstable car.

Mounting the LR trailing arm with the inner pivots towards the center of the car coupled with the J-Bar running downhill from the pinion to the frame will pull move the LR tire back during roll promoting under steer.

By thinking out the trailing arm angles in conjunction with the J-Bar angle you can guide the rear end housing on the path that helps your set up through the turn. Running the J-Bar higher on the frame side will push the rear end housing to the left through roll. If you run the frame side lower or level the rear end housing will move right through roll. Using the J-Bar mounting angle to in conjunction with trailing arm angles both up and down and left to right gives you another tool in your arsenal helping you to achieve faster lap times.

A slotted pinion mount allows you to quickly set the J-Bar angle. Running the J-Bar higher on the frame side as compared to the pinion side moves the rear end to the left through chassis roll. Understanding how the rear end moves gives you adjustment options to dial in your set up for added speed.

Using trailing arm brackets with multiple trailing are mounting holes gives you additional adjustment options. The clamp type aluminum brackets allow you to mount the trailing arm left to right mounting location where ever you want. You can fine tune the trailing arm location and trailing arm toe settings by using spacers to set the left/right angle to meet your needs.

I recommend running the top link with a fair amount of anti-squat built into the adjustment and a downhill angle of around 4 to 7 degrees. If you run a track where the car is tough to hook up you can get some added bite to the LR under acceleration if you mount the top link closer to the LR wheel. If a track you run is consistently tight then mounting the top link closer to the RR will free the car up under acceleration.

A top link mount that is slotted will allow for ultimate fine tuning of your top link anti-squat settings. Top link mounts with multiple holes also work well. Adjusting the anti-squat for your car, driver and track can maximize exit grip getting your team to the finish line first.

Top link mounting ears with multiple holes or slots will give you more room for adjustability. You can choose mounting ears that have the adjustment holes offset behind the center line of the rear end housing which will add more anti-squat under acceleration. Keep in mind that anti-squat only takes advantage of the available grip through the use of mechanical leverage. Excessive amounts can cause a loose in condition or wheel hop. Occasionally the driver might report that the front wheels feel light under acceleration at the late apex point – if so you should dial back the top link angle and anti-squat for driver feel.

As a general guideline – more anti-squat in your three link suspension works best if you run low amounts of wedge. As wedge numbers increase then you should consider lower amounts of anti-squat. Again, you can make adjustments based on your set up. I prefer low amounts of wedge in an asphalt late model and most of the races that landed my teams in victory lane had 49% to 53% of diagonal. Based on those lower wedge settings I would run a fair amount of anti-squat. Typically, I would run the LR trailing arm up an inch on the front. By using the trailing arm with plenty of angle I could reduce the angle in the top link creating a more stable entry while maintaining the anti-squat I desired. If you run 60% diagonal then running the top link and trailing arm closer to level is a good starting point.

Using your three link suspension to dial in your car is a viable adjustment option that can be performed quickly right at the track. The teams that experiment with the proper three link set up can find the set up that launches their car off the corner with more acceleration to get to the checker first.

Go Forward – Move Ahead
Jeff Butcher
JOES Racing Products
09/01/09
http://www.joesracing.com/

Driver Performance

A fresh driver that is fitted comfortably to the car will have more energy to beat the competition during those long summer races. Paired with a fast car the driver that prepares to win can place himself above the crowd in simple fashion.

The first step is to ensure that your driver is comfortable in the seat. It may take a few tries and some extra fabrication but the effort is well worth it come lap 125. Seat position is extremely important and spending the time complete with ample driver feedback is essential. Pedals should be within easy reach to allow for a relaxed leg position. Shifters should be ergonomically located with radio switches in easy reach.

Mounting the steering wheel as close to the chest as possible will prevent back strain and keep your driver up on the wheel for the entire race. A larger steering wheel creates more leverage so I always recommend the largest steering wheel that will fit past your driver’s mid-section. Utilizing an adjustable steering column allows the driver to adjust steering position right from the seat allowing for fine tuning and ultimate driver comfort.

Using an adjustable steering column mount will allow the driver to adjust the steering column with a quick adjustment right from the seat, allowing for optimal driver comfort.

Using the largest steering wheel possible will increase leverage and make the car easier to turn late in the race. Mounting the steering wheel as close as possible to the driver's chest relieves pressure off the lower back.

A large drink holder will provide needed liquid helping to keep your driver in good condition throughout the event. A drink holder with a bite valve prevents siphoning so that a cool drink is available the entire night. Be sure that the drink canister is thoroughly cleaned after each event verses leaving un-used sports drink sitting in the container all week.

Be sure to clean the drink holder after each race verses letting liquid become rancid during the week.

Head rests and leg supports should be fitted to keep the driver relaxed. Care should be taken and an exit route should not be hampered by cockpit amenities. Vision is a top priority and easy access to mirrors will help your driver to see at critical moments. Side mirrors and wide view rear view mirrors are needed to increase driver awareness. Some people debate the side view mirror. In my view there is zero debate – you absolutely need a side view mirror.

Mounting the pedals so that the driver's legs stay relaxed will relieve fatigue and give the driver the energy to stay up on the wheel for the entire night.

Driver preparation begins with exercise and a pre-race meal habit that is designed for performance. Good nutrition is a full time project and eating right only on race day comes up short as compared to a proven meal regiment.

Daily hydration would include 80 ounces per day of water or sports drink. Competition hydration should start at least 48 hours before race day. On the evening before race day drink 16 ounces of your favorite sports drink before bedtime.

Eating quality food and skipping the fast food line will help you and your crew to stay sharp. Making a shopping list and a quick trip to the grocery store will put reasonable nutrition at your finger tips.

On race morning drink another 16 ounces of sports drink or water. If it is a day race drink an additional 16 ounces 2 hours prior to the event. For night races drink 16 ounces of sports drink 2 hours before the event and add and additional 16 ounces in the middle of the day. To assist in the hydration process, drink the liquid in large gulps verses sips.

During the event it is important to maintain hydration. 4 to 8 ounces should be consumed every 20 minutes. During the race a sports drink with a carbohydrate component will help maintain energy from green to checker.

Post race hydration is an important element helping the driver to recover and proper post race hydration starts a healthy cycle for the following week. With in an hour after the race drivers should drink 24 ounces of water or sports drink and continue through out the week with ample liquid intake. Drivers that sweat excessive amounts should replenish with 24 ounces of liquid for every pound lost during competition.

Caffeinated beverages should be avoided in the 48 hours before a race. Alcohol should be avoided in the 48 hours before race day as well. Cool water is absorbed by the body more efficiently than warm water – somewhere around 55 degrees seems to work best.

Proper race nutrition will help keep your driver in winning position. Foods high in carbohydrate provide the needed energy for endurance. The science states that carbohydrates fuel muscles and they breakdown it smaller sugars providing the energy for optimal performance. The sugars glucose, fructose and galactose are stored in the body. These sugar stores prevent muscle tissue breakdown during competition.

Energy bars, energy drinks and fruit are a good source of carbohydrates. Pasta, rice and bread contain needed carbohydrates and racers looking for an edge should load up 48 hours prior to grueling races. On race day a solid meal 4 hours before the race will provide valuable energy and give the body time to reap the benefits. A complete meal should be followed up with a sports drink one hour before the race.

Eating food high in protein completes the racers diet. Foods such as Beef, chicken, fish, milk, cheese, peanut butter and eggs are the choice of top racers. Champion racers eat a balanced diet of high protein foods to stay sharp. Protein repairs and rebuilds muscle fiber and assists in carbohydrate storage.

Fat is a needed ingredient in the sports diet but fatty foods should be avoided on race day as the body takes a long time to covert fat into energy. While tempting, racers should avoid donuts, burgers, meats, fries, chips and candy bars on race day. The fat content takes the body a long time to digest and the slow digestion diverts energy at game time.

Racers should stick with proven foods on race day. Each body is different and experimenting with a new food routine on race day or even the day before could lead to nausea and discomfort at the worst time. All athletes should pay attention to their bodies and only eat foods that they know will agree with their system.

Eating right just on race day will not produce competition results. A solid routine starts early in the week and peaks on race day. Exercise will assist the body in converting food into energy and a fit driver will excel regardless of the conditions. Helping your driver to be healthy is as important as the winning set up. Keeping your driver up on the wheel for 200 laps will create more wins. Really, the entire crew will be more efficient if they prepare their bodies with as much effort as they place on the racecar.

Below is a loose meal plan that has been tailored to be practical for racers. Olympic athletes follow a strict diet that would simply be too hard to follow for most racers and their teams. The suggestions below are designed to be obtainable for the racing crowd.


Sunday (Recovery Day)

Breakfast - Eggs, non fat milk and English muffin w/peanut butter

Lunch - Tuna sandwich, celery, pretzels

Dinner - Flank steak, red potatoes, peas, salad, apple juice

Monday

Breakfast - Grapefruit, whole grain cereal, non fat milk, cheese stick

Lunch – Turkey sandwich, oven baked Tostitos, apple

Dinner – Boneless/skinless chicken breast, pasta, string beans, salad


Tuesday
Breakfast – Oatmeal, low fat cheese, non fat milk, orange

Lunch – Roast beef sandwich, pretzels, yogurt

Dinner – Fish, brown rice, broccoli, mixed green salad, V-8 juice


Wednesday

Breakfast – Eggs, English muffin, orange

Lunch – Burrito, apple, V-8 juice

Dinner – Boneless/skinless chicken, corn, pasta, salad, juice

Thursday

Breakfast - Cream of Wheat, strawberries, toast with peanut butter, orange juice

Lunch – Burger, grapes, sports drink

Dinner - Pork chop, brown rice, peas, salad w/shrimp, apple juice

Friday

Breakfast – Eggs, toast with peanut butter, grapefruit, V-8 Juice

Lunch – Chicken salad sandwich, apple, pretzels, sports drink

Dinner – Spaghetti with tomato and meat sauce, garlic bread, cauliflower, salad, water

Saturday (Race Day!) - Recommended competition day food suggestions per the American Dietetic Association:

4 hours prior to the race

Fresh fruit
Fruit and/or vegetable juice
Bread
Pasta with tomato sauce
Baked Potato
Energy Bars
Cereal with low fat milk
Low fat Yogurt
Toast with peanut butter, lean meat or low fat cheese
30 oz of a sports drink

2 hours prior to the race

Fresh fruit
Fruit or vegetable juice
Breads
Low fat yogurt
Sports drink

1 hour prior to the race

Fresh fruit
Fruit or vegetable drinks
12 oz of energy drink

Within 1 hour after the race

Energy bar
Sports drink
Fruit

Within 2 hours after race

A complete meal

Between meal Snack ideas:

Fruit (Blueberries, apples, oranges, bananas, grapes, strawberries, raspberries, peaches), celery, pretzels, oven baked chips, soft corn tortillas with non fat cheese, low fat low sodium crackers with peanut butter, low fat yogurt, whole grain cereal with non fat milk, peanuts, almonds, sunflower seeds, non fat cheese sticks, Wheat Thins, Ritz, and Triskets.

A driver and crew that are well fed on a diet other than hot dogs and beer will be able to prepare the car and find ideas to keep the driver comfortable in the car. Proper diet and hydration will allow your team can take advantage of the winning set up by keeping the driver up on the wheel when the competition wears out. Eliminating fast food and replacing high fat foods with a reasonable diet requires simple pre-planning and can be easily adapted by any team. A quick trip to the grocery store will make quick trips to victory lane a repeatable healthy habit.

Go Forward – Move Ahead
Jeff Butcher
JOES Racing Products 8/1/09
http://www.joesracing.com/

Setting The Bar

Evolution in racing has created new set up options. Installing and adjusting your sway bar correctly will help you to achieve repeatable speed. Whether you run a standard 1 1/8” bar or a 2” big bar you team should have a reproducible routine to ensure the bar is loaded as anticipated every time.

Whether you use a standard one-piece bar or a three-piece big bar, your sway bar will work more efficiently if you mount the link that connects to the lower control arm at 90 degrees.

Upon arrival at the track and with your car race ready it really pays to set up your scales on the most level ground you can find. Shim the scale pads if needed and mark the pad location so that you can weigh the car at the track in the same spot. Once the scales are set up, weigh the car and record any difference that might be created due the track ground not being level as compared to your shop set up. By establishing a baseline at the track, you will be able to make adjustments and use your baseline to maintain proper loading of the bar, ride heights and wedge. An established baseline will help to get you back to your desired numbers even after many trackside changes. Check the sway bar at the track, with the car on the scales, and note any difference in preload as compared to when you set the bar in the shop.

With a standard 1-1/8” bar and your car in race ready condition I recommend setting the sway bar on perfectly level ground. Race ready means that the next thing your car does is head right on the track. Full of fuel and everything set. Your shop should have marked places on the floor so that the car is weighed in the same level place each time. Spend the time to make the scale pads are perfectly level in your shop.

Setting the bar on the scales allows you to verify that the wedge is set to the desired number every time. With a standard set up and 1-1/8” bar setting the bar with the driver in the car works best. When the driver is in the car you make your adjustments accounting for the 12 pack of beer and large pizza your driver consumed during the week. Set your ride heights, stagger, air pressure, front to rear balance, and wedge. Be sure the fuel tank is full. If you run high rebound adjustable shocks make sure to open them up for the set up routine or have a set of dummy shocks of the same brand that are used only in the shop for set up purposes.

Personally, with a 1-1/8th inch bar I recommend loading the bar ½%. Many teams choose to run the bar neutral which is just fine. I always felt that the ½% preload helped the driver get into the corner. If your driver is smooth, and your corner transitions are modest, then neutral can help keep the care free in the middle. You can create your own preload setting and adjust as needed at the track but having a routine is the goal.

With a big-bar Mike Leary of Leary Racing Shocks recommends adding wedge to the car by preloading the bar. Leary sets the wedge in the springs and then adds additional wedge with 3-6 turns of preload and sometimes has winning success using 9 turns. There is some debate here as some chassis experts think big bars are too sensitive and they prefer to run them neutral - Chuck Carruthers is in this camp.

With a big 2” bar there is debate on how to establish a set up routine. I see teams that have their crew jump on the front bumper to get it down to the stops where they then set the bar. This may work for some teams but I think there are too many variables for this procedure to be consistent. Even with a big bar set up, I recommend setting the bar at ride height. Mike Leary of Leary Racing Shocks likes to use the big bar to add wedge to the car. Mike recommends setting minimal wedge in the springs and then adding 2 to 4 percent of additional wedge in the bar to reach your desired wedge total.

If you are running a bump stop set up west coast set up guru Chuck Carruthers recommends pulling the springs and letting the car sit down on the stops. Chuck then sets the bar neutral with the car on the stops and with the driver in the car.

The one time it might make sense to have your crew stand on the bumper is when you are running a LF coil bind set up. Setting the bar with the coils bottomed out provides for fixed compression against a solid surface. If you run coil bind in the front, Carruthers recommends loading the bar 3-5 turns once the coils have reached the bind point. Coil bind set ups are really reserved for teams that can afford testing to work out all the bugs.

Using a frame rail slider system to mount the sway bar allows you to move the sliders for perfect sway bar alignment with the lower control arms reducing binding and increasing consistency.

Mounting your sway bar properly is very important. Ensuring that attachment points run 90 degrees and are free from binds helps to keep your car fast. Awkward angles can create binding through travel making car performance unpredictable.

Utilizing bushings to support the sway bar in the bar eyes is a vast improvement over letting the bar grind against old style steel sway bar eyes. Installing slider sway bar mounts on both frame rails allows you to adjust the bar location so that your bar stays lined up even if you switch to different length arms giving you more adjustability in your car. Some sway bar arms have multiple holes to connect to the lower control arm. Shortening the sway bar arm increases the effective bar rate and with the slider bar mounts you can move the entire bar to keep the links 90 degrees for optimal performance.

Using sway bar eye bushings keeps your bar running smoothly and eliminates binding. A swivel eye self adjusts for perfect alignment. This swivel eye is removable allowing the bar to be dropped out the bottom for quick sway bar changes.

Swivel adjustment eyes allow you to use a ratchet to load the bar making for quick and easy adjustments. The swivel system allows you to preload the biggest bars with ease. The swivels prevent binding and self adjust keeping in line with the bar. Quick sway bar changes can be made as the swivel eye unbolts allowing the bar to be dropped out the bottom.

Adding preload to a sway bar effectively increases its rate. If your team feels you need a bigger bar you can wind in some load to see if you are going in the right direction before spending the time to change out the entire bar. Moving the sway bar links just one hole has a profound effect and is another adjustment option.

If your car is a little loose on entry then adding preload to the bar can help to settle it on entry. A bar that is neutral or set slack can, at times, cause a loose entry condition. A quick preload adjustment can be made during practice and your driver can give you an instant report. My feeling is that race teams should do everything in their power to avoid a car that is loose on entry. If your car is tight in the middle the driver can compensate with a different line to help minimize the push. With a loose entry condition the only thing the driver can do is to slow down. Loose entry should be avoided at all costs and in this condition winding turns in your sway bar may be good fix.

Choosing the right bar is difficult. The best way is to consult with your chassis builder and simply watch what your competition is doing. At many tracks it remains to be seen if the new big bar concept is better than the traditional bar set up. Most crew chiefs agree that the big bar set up is good when you hit it. The offsetting factor is that the big bar concept is finicky and you can be out to lunch as soon as the smallest variable is introduced. For less experienced drivers a standard bar set up is going to produce more feel helping them through their learning curve.

Whether you use a standard bar or a big bar establish a routine so that your sway bar is set the same way each and every time. When you preload a sway bar the increase in rate is exponential as you add turns of load. Teams should experiment with the car on the scales and record the wedge number increase with each turn. Charting the wedge change with each turn of preload only takes a few minutes and it will give teams the information they need to make precision changes at the track.

The bottom line is that a smooth operating sway bar that is installed free of binds will make your car faster. The precision parts available today offer an advantage. In the past, one piece sway bars were simply bolted in and taken for granted. Your team can find consistency and extra speed by tuning up your sway bar installation coupled with a sound routine for loading the bar.

Go Forward – Move Ahead

Jeff Butcher
JOES Racing Products, Inc
7/1/09
http://www.joesracing.com/

Short Track Aerodynamics

Short track racers can create more down force than their competition by spending the time to take advantage of the leeway permitted by fiberglass bodies. Corner speed can be improved by the teams that massage the body panels and push the limits of the rules. Depending on your division, there may be significant down force gains due to the lack of templates and/or enforcement. Cup teams have to live with the Car of Tomorrow and have less room than ever to stretch body panels. Short track late model teams have plenty of room to achieve maximum down force.

Down force is your friend. Just about all late models run on tracks that are under a mile in length. Corner speed is enhanced by applying every trick to create down force as drag is of little consequence for short tracks. Occasionally, race teams have asked me if they should lay the rear spoiler down on larger tracks to reduce drag. In general, you want the maximum spoiler angle allowed up to about 75 to 80 degrees on tracks 1 mile and under. More spoiler angle creates down force at the rear wheels helping to launch you off the corner. With the good initial run off the exit the engine horsepower gets your car off to a good start and the added drag on the straight is not worth considering. If more spoiler angle lets you get the throttle to the floor sooner then you will go faster and the effects of drag on the straight are not enough to take away the solid start off the corner.

Keeping your spoiler in the wind with plenty of spoiler supports will add consistent down-force at the rear wheels, helping to launch you off the corner.

Using your rear spoiler for down force is critical. You want to guide air off the roof and down the rear window with a smooth transition to the deck lid. Sometimes bodies have a sharp transition from the rear window to the deck lid area. If your rules allow you want to push up the deck lid to create a smooth transition to the rear window.






A smooth transition from the rear window to the deck lid area will reduce turbulence and allow the air to stick to the deck lid, flowing smoothly over the rear spoiler. Push the rear window up where it meets the deck lid as high as possible.

Fiberglass bodies allow for many options to create down force where you need it. You should consider your goals before mounting a new body. For example; if your car or track has a tendency to be tight (push) then you can help the problem by stacking the body to the front. Moving the body an inch forward is going to increase front down force significantly. If your car or track is consistently loose then setting the body back an inch is the way to go.

When mounting your body your goal is to have smooth and rounded transitions. If you can imagine airflow and think of air as wanting to stick to or follow your body lines. Sharp inside or outside body angles should be avoided at all costs as they create turbulence disrupting the air flow. Long rounded transitions allow the air to follow along the body and assists air in its natural tendency to follow surfaces.

During the next television Cup race pay attention to how the cars appear to track in comparison to the wall. You can visibly see how the bodies are mounted on an angle as compared to the centerline of the chassis. Engineers have discovered that they can pull the left front over and over hang the right rear quarter panel over the tire. Extending the RR out and keeping it in the wind creates down force on the RR which helps the car be more stable on corner entry. Skewing the RR quarter panel out keeps the spoiler in the wind on corner exit planting the RR for improved acceleration. Over hanging the body at the LF creates added down force on the tire that has the least load. With the front body panels offset to the left the car cuts better though out the turn. With a fiberglass body you can easily move your mounting points and mount your body on an angle for added speed.


Sealing the nose to the ground is paramount to making speed. Eliminating front lift and giving air the right start over the entire body equals more speed. This car has a "down force" body. If your rules allow, the wide panels and extra length are worth the investment.

The main reason a Big Bar Soft Set up works due to today’s bodies – they simply create way more down force than the vintage Camaro fiberglass bodies. If you go to a Sprint Car race on the dirt ask yourself which is faster; a winged Sprint car or a non winged Sprint car. On your late model your fiberglass body has significantly more surface area than a Sprint Car wing. Your assignment is to use the entire body to your advantage.. Sealing the nose piece to the track is the key to your Big Bar Soft Spring set up. Sealing the nose forces all of the air over the body. Any air that leaks under will cause lift and down force is lost. Making an adjustable valance will allow you to keep the nose down on the track with a combination of track conditions and car set ups.


An adjustable front valance will let you drop the nose right on the ground with a quick track adjustment. Getting the nose down for a perfect seal is a high-priority down-force item.

Your body should be a rigid structure at race speed. Any panels that are flapping are slowing you down. Flapping panels create unwanted turbulence and upset the airflow in an unpredictable fashion. If your front windshield and rear window deform in the wind you need to add supports until they are rock solid. Your rear spoiler needs to be solidly mounted and the use of several spoiler supports is a good idea. Fender supports should be used and attached at multiple points on the body to hold panels firmly in place.

If your hood deforms and flaps at speed not only are you losing down force but you are also diverting air away from the cowl intake potentially cutting critical air to the carburetor resulting in a loss of horsepower. Take the time to make sure your body panels are solid in the wind.



Using body braces to hold your body panels in place will give you a rigid foundation for maximum down force and air flow. This nose peice is clost to vertical at the sides. If you can, stretch the nose peice side panels out and let them angle back to the headlight which will make you more downforce.

The nose piece is a critical element. If your rules allow then pull the nose piece out at the front of the tires as far as possible. If allowed stretch the bottom of the nose piece out along the bottom edge. The idea is to create a sleek angle verses having a bulldozer at the leading edge. An angle from the top of the hood to the track equals down force. Even the sides of the nose piece can be stretched out. If the sides are perfectly vertical then you are leaving a few extra pounds of down force on the table. If the nose piece angles out from the headlight down to the bottom edge you create surface area for air to push down on and more speed is found. If your rules enforcement is soft then add a splitter to the lower lip of the nose piece which will add front down force.

The fender wells are another area where attention to detail pays off. You can trim the fender wells at the right side of the car to fit closely to the wheels. On the left you can keep the front edge close to the tire but you must provide ample clearance from the top of the tire extending around the fender opening to the ground. It is critical to leave an escape route for air that gets trapped under the hood. If there is not enough escape area to relieve the air pressure from under your car will see lift and could be unstable at speed.

Exchanging down force for drag on a short track is nearly always a good idea. That said – be sure to avoid any parachutes. Make sure the front side of the wheel wells extends to the outside more than the opening on the backside of the wheel well. Be sure the windshield posts are slightly outside the window posts at the quarter window.

If your rules allow, you can use your body braces for a few extra pounds of down force. As the tires spin at speed they create wind. Placing panels or body braces to catch the wind from spinning tires equals more down force. While small improvements add up for added down force a major gain is found if your rules allow a “down force” body. The extra wide panels and longer length are the source of valuable surface area. More surface area equals more down force. If your competition has a down force body and you have a template body it is truly and unfair advantage.

Finding extra down force is like removing weight from your car – you discover improvements a few pounds at a time. After discovering the big gain areas you can tackle the small areas. A few pounds of down force here and a few there can really add up. Make sure the leading edges of everything on the underside of your car are rounded. Allowing air to move freely under the car adds to the down force numbers. If you can make sure the rear bumper cover is rounded at the bottom edge to allow air out from behind the car.

Go Forward – Move Ahead
Jeff Butcher
Courtesy of JOES Racing Products
5/31/09
http://www.joesracing.com/

A-Arm Science

Rolling through the center of the turn at maximum speed requires a suspension that is free of flex yet moves smoothly with out binding. A-arms have improved dramatically and choosing the correct A-arm will help you to create suspension systems that are faster and more consistent.

There are many things to consider when selecting the A-arm for your car. For dirt cars many racers have utilized arms that split at the bolt in ball joint allowing the a-arm to be opened for installations where the A-arm wraps around the frame mount. The split causes additional flex and high quality versions should be considered. The split A-arm utilizes a bolt in ball joint. Many top teams are switching to low friction screw in ball joints for better performance.

We built this fixture for this test which can apply from 0 to 1500 pounds of force right at the ball joint emulating the conditions seen on your car. We can also set up the fixture to cycle A-arms repeatedly for destructive testing.


Buying an A-arm shaft with simple drilled holes is a less expensive option yet using an A-arm with slots gives you repeatable adjustability. Successful teams keep an inventory of A-arm slugs on hand and pre-measure the caster at each increment in the shop. Pre-measuring lets teams experiment at the track with the confidence that the caster readings will be spot on. Utilizing the slugs creates a precision locating method helping to dial in the set up with quick caster changes right at the track.






Billet A-arm spacers help to maintain your settings when making changes at the track. These tapered shims keep your A-arm shaft straight preventing binds.

Machined A-arm spacers have replaced the days of caster camber washers falling all over the ground. A-arm spacers can be purchased in straight or tapered styles helping to keep A-arm shafts straight eliminating binding.

To further speed the job many teams use a A-arm nut plate that holds the backing nuts allowing use of one ratchet on the front side. Crew members appreciate avoiding the hot headers while holding an end wrench at an awkward angle.


Beyond choosing a slotted version or the basic single hole version, special attention should be paid to the tolerances between the steel A-arm and the shaft. The tolerance is critical as not enough clearance leads to binding and galling. Too much clearance creates unwanted movement and caster change especially under braking. At times excessive clearance can lead to chattering and an unstable car. In dirt applications too much clearance can allow dirt to crawl between the housing and the shaft and the grinding action causes premature wear, sticking and increased friction. Quality A-arm manufactures hold the tolerance for optimal performance.



4 Bearings spread out the load and this version has a machined bearing housing to keep the shaft in perfect alignment for lower friction.

As the suspension rolls and rides over bumps the A-arm is worked up and down continuously. For more consistent performance many teams are going to bearing style A-arms to eliminate friction. Teams are finding that with roller bearing A-arms that they can sometimes run slightly less spring rate due to the reduced friction. A-arms last longer as the bearings prevent the wear created by the steel A-arm tube contacting the shaft. Heat expansion from the headers and brakes can negatively affect standard A-arms if manufacturers do not use proper clearance. Bearing A-arms effectively eliminate the heat issue.



Bearing Style A-arms reduce friction for smooth roll and repeatable performance on the track. This version has a machined bearing housing allowing racers to replace just the steel tube section for quick adjustments or crash repair.

The smooth action of the bearings builds consistent suspension roll and increased corner speed is obtained over a long green flag run. The tight tolerance and low friction of bearing style A-arms eliminates variables allowing crew chiefs to make chassis adjustments with the assurance that the suspension is rolling up and down in a repeatable free flowing fashion. Removing the binding found in less expensive A-arms creates speed as the adjustment decisions are not chasing inconsistencies. Each crew chief decision becomes more effective and every racer should strive to eliminate variables for consistent speed week in and week out. Quality A-arms are powder coated for a premium finish where as less expensive models are spray painted which quickly wears off.

Adjusting the car with A-arm length can be very successful. Shorter RF A-arms create more camber gain and might help you to improve your tire sheet readings. Shortening the RF A-arm moves the front roll center up and to the right. At times the quicker reaction of the RF suspension, due to a shorter A-arm, can improve lap times. Experimenting at your track with A-arm length is just as effective as making a spring change. New A-arms on the market allow you to change the steel A-arm tube section while leaving the shaft bolted to the frame. These new designs speed trackside changes and reduce costs as racers can carry different A-arm tube sections without the added expense of extra shafts.

Big Bar Set Ups generally use longer A-arms than conventional set ups. Camber gain adjustments that line up with your Big Bar Set Up is a critical piece to the puzzle. At times teams jump between a conventional set up and a big bar set up. The A-arms with a bolt on section speeds the A-arm changes that are needed.

Utilizing low friction ball joints with your bearing style A-arm further enhances free movement of the front suspension. Some low friction upper ball joints are adjustable giving racers another adjustment. Fine tuning A-arm angle with the upper ball joint allows for quick roll center adjustments and easy experimentation. Adjustable upper ball joints can be used in conjunction with slotted frame A-Plates. Slotted A-plates allow the inner pivot of the A-arm to be moved up and down and slugs secure the inner pivot in place. The A-Plate slugs are manufactured for precision adjustment in the up/down axis offering another roll center tuning tool.


The weld on this A-arm is suspect. With out a proper weld bead flex and cracking can occur. High quality A-arms use thick wall .095 tubing and are TIG Welded.

Some A-arms flex more than most race teams think. Prominent teams test the flex of new A-arm brands before they end up on their car. Manufactures that use thick wall .095 tubing know the slightly more expensive tubing reduces flex as compared to .083 which is commonly used. TIG welding is another feature that will reduce flex. Poor quality wire feed welds make for limp noodles verses a rigid A-arm system. Be sure to inspect the weld quality before purchasing A-arms for your rocket.



Shaft type has an effect on flex. Choosing lightweight aluminum for the cross shaft comes at a price – aluminum flexes more than steel and racers should consider if the few ounces of saved weight in an aluminum cross shaft is a good trade. Our test results show that the steel shaft attached to a 9.5” A-arm flexes .110” at 600 pounds of force where as the aluminum shaft flexes .150” at the same force.



For this test we used our custom flex testing fixture applying force ranging from 200 lbs to 750 lbs. The dial indicator illustrates the flex difference between top brand A-arms and less expensive imitations.

A-ARM Flex Chart
.

9- ½” Bearing Steel Shaft No Name Brand

Flex at 200lbs = .060, at 400 lbs = .100”, at 600 lbs = .135”, at 750 lbs = .155”
.
9- ½” Bearing Steel Shaft Quality BrandFlex at 200lbs = .040, at 400 lbs = .075”, at 600 lbs = .110”, at 750 lbs = .130”

.

9- ½” Bearing Aluminum Shaft Quality Brand

Flex at 200lbs = .056, at 400 lbs = .105”, at 600 lbs = .160”, at 750 lbs = .200”
.

9- ½” Alum. Shaft (no slot) Quality Brand

Flex at 200lbs = .056, at 400 lbs = .105”, at 600 lbs = .160”, at 750 lbs = .200”

.

9- ½” Steel Shaft (no slot) Quality BrandFlex at 200lbs = .050, at 400 lbs = .075”, at 600 lbs = .110”, at 750 lbs = .130”

.

9- ½” Steel Shaft (no slot) No Name Brand
Flex at 200lbs = .090, at 400 lbs = .125”, at 600 lbs = .185”, at 750 lbs = .225”

Our fixture for this test was designed to apply varying pounds of force. The flex chart shows the movement associated with applying lateral pressure at the ball joint center line. The fixture is rigid and the frame mount is the same as you would see on your car. The goal in building the fixture was to emulate what your A-arms see in your racer.

Teams that reduce friction and flex will take another step forward. Racing continues to evolve and teams demand better pieces to find speed. Luckily manufactures are stepping up to the challenge.

Go Forward – Move Ahead

Jeff Butcher
Courtesy of JOES Racing Products
5/1/09
http://www.joesracing.com/

Rolling Resistance

Finding speed a little at a time is the way to the front. A few horsepower here, less drag there coupled with a good shock change might add up to half a tenth on a good day. Reducing rolling resistance is one of those speed secrets that works continuously but it is hard to measure in the real world. Still – if your car has less rolling resistance common sense dictates that your race car will be faster.

Cup teams go to great lengths to measure improvements in rolling resistance. Several Cup crews have travelled to a hidden hill to test their ideas relating to reducing rolling resistance. The teams drag the car up to the top of a steep hill and set up to test roll the car down the steep grade to determine how far it will roll with out the help of the motor. They let gravity propel the car until it rolls to a complete stop. Teams test different roll resistance ideas celebrating the smallest improvement in free roll distance.

While your team may not be able to test rolling resistance on a secret hidden hill you can try some of the latest rolling resistance tricks. Running your hubs “wet” with low friction bearings and seals will reduce rolling resistance and increase car speed. You can really feel the difference based on the effort of pushing your car through the pit area. Oil filled hubs are the new rage and coupled with low friction seals you get many benefits. One spin of the hub with your hand is enough to illustrate the reduction in friction.

John Zaretske of JZ Motorsports likes to run oil filled hubs for improved speed. Low friction seals and bearings combined with 85/90 weight gear oil result in hubs that spin freely. John also likes the maintenance aspects of running oil filled hubs. Zaretske says: “Rebuilding and re-greasing standard bearings is an all night job – with oil filled hubs I can quickly drain the oil and inspect the fluid just like I inspect motor oil in a screened filter. Each week, if the hub oil is clean, clear and free from metal particles I just refill with 4 ounces of new fluid and I am ready to race”. John goes on to say: “in the rare event I need to replace my oil filled bearings, the job is much faster because I can just pour in the oil instead of making a time consuming mess packing bearings with old school grease”.

When running the hubs wet it is important to add the right amount of gear oil. 4 to 7 ounces is recommended by the car builers we surveyed and your team should monitor the fill level to ensure proper coating of your bearings. High quality synthetic lube is required.

You can experiment with the right amount of oil if you run your hubs wet. Zaretske recommends 4 ounces but other builders and hub manufactures may have their own recommendation. Our survey of car builders resulted in a recommended hub oil fill range from 4 ounces to 7 ounces utilizing synthetic fluid. As running hubs wet is a new speed secret you should keep an eye out as the fill level recommendations will change based on testing, fluid type and the evolution of manufactures specifications.

Weekly draining and refilling of "wet" hubs is simple. Fresh oil helps your parts and their longevity. Using a locking hub nut will ensure that your hub maintains torque even at lower torque settings.

Chuck Carruthers of Chuck Carruthers Industries says that only 5% of his customers are running hubs wet. Carruthers states: “Using Teflon coated bearings with 4.25 ounces of 50 weight synthetic gear oil gains 6 to 8 coast down horsepower”. Chuck prefers traditional wheel bearings and pays the extra cost for the Teflon coated version. Chuck feels the low friction roller ball style bearings are risky in long races. Carruthers says; “we get plenty of friction reduction from Teflon coated roller bearings and would rather avoid the added wear seen in roller ball bearings”. At Carruthers Industries they are careful and run the minimum amount of hub oil to ensure parts are coated but avoid running too much fluid as excess fluid in the hub can actually add heat. Chuck says “you want enough fluid to coat the bearings but any surplus fluid can foam or even impact how heat transfers and dissipates through the hub”.

Low friction roller bearings or Teflon coated tapered bearings will lower your rolling resistance where you need it most. Roller ball bearings should be inspected often and need continuous maintanance.

With the “wet” system and Teflon coated bearings Chuck recommends running 15 to 20 ft pounds of torque on the front hubs. He advises that you can run less on the rear as the brake heat is less intense. Chuck says 10 to 12 ft pounds on the rear hubs works great. Reduced preload on the bearings reduces rolling resistance creating more speed. Chuck reminds us “be sure to use a locking hub nut to ensure your torque setting stays put from cold to hot”.

We temporarily installed a clear cover to show the fluid level with 4.25 ounces of oil at 2 degrees of negative camber. A quick spin coats the bearings and races evenly.

Carruthers pays attention to detail and has made a special hub adapter for measuring hub torque. Chuck advises: “When our customers are doing their own work we have them torque the hub nut to our recommendations with a good foot pound torque wrench – we give them the setting and they simply torque down the hub nut and lock it down. For the cars that we maintain in our shop we go the extra mile and use a hub adapter that connects to a high quality inch pound torque wrench – the adapter connects to the torque wrench at the hub center. We add oil and give the hub a spin ensuring the hub and seals are lubricated. We then use our inch pound torque wrench with our custom made centering adaptor. We adjust the hub nut until we have 28 inch pounds of drag torque when rotating the hub with the torque adapter at cold temperature. When the hub is hot we know that there is minimal torque on the hub providing for optimal reduction in rolling resistance. At race temp we see about 3 to 4 inch pounds of drag torque with our custom measuring device”. Care should be used with this process as if the specs are not followed exactly you could end up with too little torque resulting in failures. Weekly inspections and pre-race checks are needed when pushing the edge in this fashion.

Rubber seals are the source of friction. You can easily feel the dramatic difference in spin effort from low friction seals as compared to traditional rubber seals. The added expense can be offset if your hubs have a seal retainer system.

While at the 2008 PRI show a confidential source explained the secret testing their team performed relating to floating rotors. Since my confidential source did not want to get fired by his team he wants his name kept out of this article. The secret tests performed by his high profile team revealed that running floating rotors added 6 horsepower on the chassis dyno. Making 6 horsepower due to brake efficiently – seems crazy! The HP gain is due to the floating rotors finding center through out the heat expansion range. The T-nut set up and rotor flange allows for a bit of movement that absorbs rotor warping and isolates it from the hub resulting in less brake pad drag. You get the horsepower gain and the brakes run cooler due to less pad and rotor contact. Drivers report smoother braking with reduced pulsing adding to the efficiency of the braking system. Here we go – a little more speed created by removing unwanted friction.

Using a floating rotor with a T-Nut package allows the rotor to expand through the heat range. The movement allowed by the rotor flange is isolated from the hub resulting in less drag. This hub has a seal retainer system that lets you remove and replace expensive low friction seals with out damage.

Another way to reduce rolling resistance is to square your rear end. There are many thoughts on rear end set ups but I like to keep this simple. I make sure my rear tires run nearly parallel and make sure the rear end is set square in the car. When building a rear end I make sure both tires point straight ahead and then I toe in the RR tire 1/32 of an inch. I figure at speed and under load that the RR will pull back that much and when it counts the rear end is perfectly square. A square rear end will not have any drag as compared to running toe out with the tires dragging all the way around the track. We know Cup teams play around with rear toe settings for aero advantages but for short track racing a square rear end will be more consistent and it will reduce your rolling resistance.

Equally important is the front toe setting. It is common for short track racers to run 1/8th inch or so of toe out and this spec has been around as the standard for a long time. I think the thought process is different now as compared to a few years ago. Today I recommend rethinking the toe out setting in the front end. Our components are simply manufactured better today and there is less free play in the front suspension pieces. A-arms are stronger, racks are better, rod ends, ball joints and tie rods are all built with tighter tolerances. I would recommend running 1/32nd of toe out or even zero toe out in the front. With the tires pointing straight ahead you can find more speed and eliminate tire drag from excessive toe out.

Ackerman should also be considered. Ackerman is sometimes used as a chassis adjustment but the Ackerman effect and additional degrees of steering at the left front tire creates drag. Keep in mind the amount of tire drag you are adding to the car if you have Ackerman toeing out the LF tire as you turn. Excessive Ackerman can sometimes cause a hitch when the driver picks up the throttle. As the power is applied to the rear tires they have to push against and overcome the Ackerman drag on the left front. Depending on the situation the car may break loose or simply not leap off the corner due to the Ackerman drag. Ackerman can be a great adjustment but thinking out the rolling resistance considerations may find you additional speed.

Aerodynamics is another area where rolling resistance gains can be found. Air likes to follow body surfaces and air needs smooth transitions to prevent unwanted turbulence. When ever possible create smooth and rounded body transitions verses letting air fall off of sharp corners or cliffs. When massaging air try to mold the body to allow air to follow surfaces avoiding surprise edges or cliffs.

As race cars have evolved reducing rolling resistance may help make up some of the power limitations created by crate motors, 9:1 compression motors, and carburetor rules. Embracing rolling resistance and massaging your car with a friction free approach may “find” you 15 to 20 new horsepower. If you are running a 400 horsepower crate motor you could end up with a net 5% improvement in power! Even with unlimited horsepower the teams that work hardest on reducing rolling resistance will create horsepower that just might be the nudge you need to get you ahead at the photo finish.

Go Forward – Move Ahead

Jeff Butcher
JOES Racing Products, Inc.
3/31/09
http://www.joesracing.com/

Shock Specialists

Shocks are an important tuning tool that create feel in your car. With the variety of shock brands, components and types partnering up with a shock specialist can help you to navigate through the vast array of component offerings.

To increase our shock knowledge, we have interviewed two successful specialists in the shock field. Mike Naake of Naake Suspension Specialists and Mike Leary of Leary’s Shock Shop offer their suggestions and experience. Both “Mike’s” provide shock hardware, setups and technology to prominent racers across the country and are authorized service centers for many of the major shock brands.

With so many shock choices on the market how can you help racers choose the correct type?
Leary:
It is important to buy the most tunable shock within your track or organization’s rules. If your rules allow for compression and rebound adjustment the additional initial investment will translate into speed. If your rules dictate twin tube designs then the more economical hardware can be maximized through tuning. When rules allow we want our teams to utilize the options that are made available in pressurized mono tube shocks.

Naake:
Rules and budget are part of the equation. We tailor our shock packages to meet the needs of each racer. After a complete interview of each team we determine if pressurized mono tube shocks will work best or if the economics of twin tube shocks meet their needs. Once the shock type is selected we continue the interview to learn more about the goals of each team and build packages based on their input. Understanding driver tendencies and track characteristics allow us to tune shocks for more speed.

What is the racer benefit for partnering up with a shock specialist?

Naake:
Drivers and Crew Chiefs can communicate what they want the car to do and we can create an option based on the feedback. We can customize and offer a linear/digressive piston, digressive linear piston, double digressive piston, and another piston designed specifically for rough race tracks. Our knowledge is based on feedback from many teams and the information base gained over the entire group would be impossible to gain within a single team.

Leary:
With shock manufactures offering ever expanding part options for their shocks i.e.: pistons, shim stacks, shafts with different bleed options, etc, it is almost impossible for the racer to stay on top of his shock program. As shock specialists we are continuously being educated on latest product offerings from the shock companies we support. Racers also benefit from our experience – we are testing all the time and the knowledge gained by working with several teams helps us to understand the changes needed for each individual team. Our shock dyno runs full time creating unique shock packages even for teams competing at the same track.

What is a Mono tube shock?

Naake:
There are two types of late model/sprint car mono-tube shocks, emulsion and De Carbon style. An emulsion shock is typically a mono tube shock with gas and oil in the same chamber. The oil and gas mix creating foam. This is not a desirable situation in any hydrologic system, especially a racing shock absorber. Christian Bourcier de Carbon invented the mono-tube pressurized gas shock absorber. A De Carbon style shock absorber has a dividing piston that separates the nitrogen and oil. De Carbon mono tube shocks with gas pressure and a dividing piston perform better than twin tube shocks. Mono tube shocks cost more to manufacture yet the added expense results in better and more consistent performance.

Naake uses this photo to illustrate the base valve action on the mono tube compression stroke. As the shaft displaces the shock oil the base valve smoothly opens to allow for the shaft volume. Shim stacks can be seen flexing to meter the precise amount of shock oil.

The Naake mono tube rebound stroke photo illustrates shock oil flow and you can see the internal forces and valving action. The mono tube gas separating piston is clearly shown at the top of the shock.
What is a Twin tube shock?

Naake:Many tracks and weekly racing series’ rules require a twin tube shock. They do this to keep the racers’ costs down. A twin tube shock has an inner tube that the piston runs in. At the bottom of the inner tube is a base valve. The function of the base-valve is to make 30%-40% of the compression force and replenish the oil in the inner tube on the rebound stroke. If a base valve is not performing with enough force in a twin tube shock that could result in cavitation or what we call in a twin tube design “dumping”. Dumping is when too much oil moves out of the inner tube too quickly and on the rebound stroke it is not replenished fast enough resulting in a momentary dead spot on the rebound stroke. The dumping can be verified on the rebound opening stroke of a constant velocity test on your shock dyno.

Naake uses this photo to show the low pressure gas filled bags utilized in twin tube shocks. The low pressure bags prevent foaming and deform to account for shaft displacement. The Base Valve adds 30 to 40% of the compression force.

Naake points out twin tube shocks have an inner tube that the piston runs in. The twin tube rebound view shows the base valve metering oil from the outer oil reservoir.
Why run a base valve?

Leary:Base valves are of most benefit on heavy cars and when low gas pressure is used. For most late models we run without base valves in mono tube shocks to save cost. As you run high compression it can make sense to add a base valve to help prevent cavitation on the back side of the piston. When running a base valve the shock valving needs to be tuned to line up with the compression forces that are metered through the base valve.

Naake:
A base valve is an optional component on a mono tube shock and works great with low pressure. Some series that allow mono tube shocks do not allow base valve to be installed. A base valve shock will have a much smoother feel to the driver than a non-base valve shock. Of course, a base valve in a shock adds to the cost. We are big fans of base valves when rules allow. The added control of the oil displaced by the shaft gives us more choices with our rebound adjustments as cavitation is eliminated through transition from compression to rebound.

Is shock oil important?

Leary & Naake:
Shock oil is a part of the shock that most racers overlook. Many manufactures use inexpensive hydraulic oil in their shocks. Inexpensive oil can vary through out the temperature range. You may start the race with a shock that has a 5 valving on compression and rebound. Inexpensive oil may react dramatically with heat and effectively make the 5 shock you built in the shop perform like a 3 shock on the track. Using thin synthetic oil reduces the viscosity change allowing for more consistent shock performance from ambient temperature to race temp.


Using a drip cup for shock rebuilding keeps the oil contained and your workplace clean. An organized shock building station is a must if you are servicing shocks on your own.



Leary tested several 5 shocks from different companies. This graph shows that a 5 shock valving varies significantly from brand to brand. Understanding the brand valving differences will help you to make the proper adjustments when using competing brands.
What Shock tips can you give to our readers?

Naake:We hear a common myth that bag shocks blow out due to rough track conditions or sudden high velocity compression. In my experience, I just do not see this at all. The only bag failures I have seen are due to errors in assembly or a bag had a small puncture prior to assembly.

You can perform a simple hand test of your twin tube style shock. Fully extend the shock. Position the shock so that the shaft end is up. Compress the shock about a half an inch. If you feel any slack or a dead spot, it is an indication of air in the system. This can be caused by the shock being low on oil, either from the shock having an oil leak or from not enough oil placed in the shock during assembly. It could also indicate a leaking gas bag. We perform this test on all twin tube shock prior to running a dyno test. If they don’t pass the hand test, they are guaranteed to fail the dyno test.

Leary:
You should have your shocks dyno’d when they are new to get a baseline, and then should be re-dyno’d after a crash and halfway thru the season. A shaft bent 3 or 4 thousandths or a tiny dent in a mono tube shock body, will change the shock dramatically. In this day in age, it is almost impossible to build your own shocks without testing them on a quality dyno. Using the proper tools such as, shock wrench, shock vice and drip cup will make the building process easier and protect your investment. Keeping your shock work area clean and organized is pivotal to building successful shocks.




If you are going to work on your own shocks then using the proper tools such as a shock vice will help you to build winning shocks.
What shock adjustment tips can you suggest?

Leary:
Most of the handling of a pavement car is controlled in the first 2 inches of shock movement. I like to use the rear shocks to control the entry of the corner, left side shocks and RF for the middle of the corner and the fronts for exit.

I avoid using the compression side of the shock for handling adjustment. I would rather use springs to control compression adjustments. The one exception is possibly the compression on the left rear – by increasing the compression at certain speeds, you can gain bite off the corner. It can make the car think is has more LR spring on exit without changing the corner entry like a spring can.

On a conventional spring setup, the shock settings will work differently than with a soft spring set-up. The more front spring rate, the less compression you need because the spring is doing the work. With a soft front spring set up, you need to use compression to control the speed of the front end movement because you have a 200 lb spring trying to hold up an 800 lb corner.

If you tie down the left rear shock on a conventional set-up, I’ve found you will tighten up the entry of the corner. I believe it keeps the left rear weight from transferring to the RR as fast, which gives you that loose entry feeling and keeps the weight on the LR tire.

With a soft spring set-up, if you tied down the LR, it usually will loosen the corner entry. Because of the rapid weight transfer to the RF of the car, we can overload the RF tire, which can cause a soft push on entry. By delaying that transfer the RF tire has a chance to “grip” the track, so the driver feels the car is looser on entry.

With either conventional or the soft spring set up, the rebound on the RF can help that “tight in the middle” feeling. By stiffening the rebound on the RF it holds weight on that tire and helps it maintain grip – it also keeps the RF from transferring weight to the LR as fast, which will cause the car to pick up a push. The downside of holding down the RF is you can lose some grip off the corner, because you are delaying that weight transfer to the LR.

When we have soft front springs, we need the rebound on the LF shock to help the sway bar to keep all that weight transfer to the RF. That is why we see the extreme tie-down LF shocks. It is important to balance your front springs/sway bar and tie-down in the LR shock. We build LF shocks at 1 inch of travel anywhere from 600 lbs of force to 1000 lbs, depending on the set up.

Changing the sweeps on externally adjustable shocks makes a big change. Leary uses this dyno graph to illustrate the dramatic effect of using sweep adjustments.
Naake:To help free up the car from the center off a quick adjustment is to add gas pressure to the RR shock. By adding up to 200lbs (if you have the right hardware) the car can take on a better attitude and become more stable on exit. This fix is quick and can be removed quickly if the driver is still looking for a better exit.

With today’s set ups we like to maintain rebound in the front shocks. If the car is tight, and if the team has the right hardware, we try to go with high frequency pistons to relieve the tight feeling. In short, there is an o-ring behind the shaft band that delays the metering of oil through the bleed holes for a brief moment and then shuts the bleeds off just as quickly. Our teams can work with us to discuss these options to find more speed – our goal here is to let your readers know that there is high tech hardware out there that goes beyond generic answers. We have proven results in gaining front grip off the corner with the high frequency hardware available. Remote canisters provide another layer of adjustability when allowed.

While high tech is cool sometimes a basic answer works well. If your car is tight then more compression in the RR will help the car turn in the center. You can try a bit more rebound in the LR to free it up. You can take a little compression out of the LF or tie down the RF to help the car turn. Extreme rebound in the front shocks is good in many cases but too much low speed control can reduce front grip. With extreme front rebound you need some bleed to allow the tire to follow the track surface.
When rules allow a remote shock canister gives you more compression adjustability options. Base valves can be built into remote reservoirs and the housing needs to be protected from damage. Using a canister mount allows for quick adjustments when practice time runs short.
Summary:

Butcher:
Shock science and hardware is constantly changing and the application of the set up tips is very dependant on the track, driver and location in the turn. Many times a standard shock tip will change 180 degrees based on moving the car a few feet in the corner and the tips above need to be applied with full understanding of shock mechanics – both Mike’s will change their adjustments based on real world data. When it comes to shocks it is all about timing and transitions. Shocks might hold or delay movements but in the end the springs carry the load. Bumps, braking, throttle and rolling through the middle all provide information that will be analyzed independently by your shock guru. Be aware that you may have soft front springs but you also must consider the overall front spring rate based on the giant sway bar that could be in your car.

Go Forward – Move Ahead

Jeff Butcher
Courtesy of JOES Racing Products
www.joesracing.com

Resources:

425.267.9199

916.771.0109