The No. 84 car driven by Shane Huffman in the USAR Hooters ProCup Southern Division handle
In the opinion of most circle track racers, good handling provides more performance than horsepower in most cases. Last month, we examined how to recognize basic handling problems and ways to correct them for corner entry and the middle of the turn. We believe mid-turn balance is the most important to overall handling performance. And entry and exit performance is very important for both overall performance and being able to race other cars and move forward through the field, even if that means passing lapped traffic. We have worked on mid-turn and entry problems, now let's tackle the exit problems.
Being loose off the corner is possibly the most detrimental handling problem we can have in an actual race. Many passes occur as the cars are exiting a turn. Other racers can recognize when you are having problems with bite off the corner and set you up by laying back a bit and making a run off the corners. You are forced high coming out of the turn and must steer more to avoid the wall. With a car that is already loose, that means backing off and letting the passing car go. This will happen with many more cars until one comes along that happens to be as loose off as you are.
A car that is loose on exit could have several problems. When we race on asphalt, this condition usually occurs on flatter race tracks and ones where the surface is worn. Some of these problems/fixes relate to both dirt and asphalt, but some will not cover both.
1.Shock Compression and Rebound Rates - If the left-rear shock is too soft on compression or the right-rear shock is too stiff on compression, the car will lose some amount of crossweight percentage momentarily as we get back into the throttle. The rear of the car and the shocks compress and the front shocks rebound. Usually, the left-rear shock should be at a higher rating for compression than the right-rear shock. This serves to increase the crossweight percent momentar-ily as the car accelerates and the rear of the car squats. Front rebound rates affect the amount of crossweight percent also. Many teams will increase the rebound rate of the left-front shock to loosen a tight car off the corners. This could be making your car too loose. Match the front rebound rates if a split is making the car loose.
There is a design for a three-link rear end that utilized a lift-arm or pull-bar where the
2. Rear Spring Rates - The combination of rear spring rates can affect the amount of traction we have on exit at the rear of the car.
If the left-rear spring is rated much less than the right-rear spring, the amount of weight supported by the right-rear and left-front wheels will increase as the weight transfers to the rear under acceleration with a corresponding decrease in the weight supported by the right-front and left-rear wheels. Since the right-front and left-rear wheel weights represent crossweight, this momentary movement reduces the crossweight and causes the car to be loose while under initial acceleration.
If possible, keep the rear springs even in rate or use a softer right-rear spring if traction is needed. In any event, make sure the setup is balanced and that changes to the spring rates are in conjunction with corres-ponding changes to the Panhard bar height to maintain a balanced setup.
The amount of rear spring split (right rear softer than the left rear) needed will vary with the type of car. A coilover late model asphalt car only needs about 10 or 15 pounds of split to get the job done. A dirt Late Model could use a 50- or 75-pound split to cause the car to roll over more dramatically with dry, slick conditions. This would cause a sufficient amount of rear suspension movement to enact the rear steer that is needed for those conditions.
A stock car with the metric 4-link rear suspension and big springs mounted in the stock location needs more split, up to 50 pounds of difference, in order to overcome the high rear moment center that is associated with that type of suspension.