asphalt adjustments

Asphalt Adjustments

Also be sure to check out the Big Bar Small Spring section of the asphalt racing help. It can be found on the racers resources page.

The very first thing you have to decide is the cause of your problem...For instance we will use this example to start out. You are racing your car on a 1/2 mile asphalt track. You are using a locking spool in your rear end. You have little to no stagger with your rear tires. As you make your transition in the center of the turn you experience a push, your car doesn't want to turn. Your problem you will find lies in the spool locking up keeping your rear wheels locked solidly together, driving your front end straight rather than letting it steer around the corner. In this case what you would do would to be add stagger to the rear end to help it steer around the corner.

Now lets take the same car on the same track already with 4" of stagger, which is at maximum or beyond the maximum stagger that you need. The car pushes at turn entry and in the transition of the turn, Where does the problem lie? In a case like this your roll couple distribution is to stiff. The car can not shift the weight when it enters the turn. You could do one of two things or even a combination. First remove some of the pre load in your front sway bar, secondly take some of the cross weight out of the chassis.

If the push is more severe you can go down to the next lightest size in the anti-sway bar. Using the anti-sway bar is one of the easiest and simplest methods of controlling over steer or under steer on an asphalt race car. Using this method will not change your ride height, suspension heights, or the geometric relationship of one suspension piece to another.

When a push is severe then a right front spring change will have to be made. Go to a lighter spring rate, or the right rear spring can be changed to a stiffer rated spring.

Balancing the chassis by bringing the operating temperatures of the front and rear tires within optimum range will maximize the lateral acceleration capability of the race car. when the chassis is perfectly balanced, on a flat to low banked 1/4 mile to 1/2 mile paved track the right front tire temperature average will be 10-15 degrees hotter than the right rear tire. Any more heat than this on the right front indicates pushing or understeer. Any less heat at the right front indicates oversteer or looseness.

When you are sorting out problems with the chassis for a particular problem you must isolate where on the track that the problem occurs. For example, the car has a push, where does the push occur/ at turn entry? in the middle of the turn? or in turn exit? A push in each location has its own symptom of a very different problem. Lets look at each one.

Push at turn entry

When this happens during braking, the problem is many times the brake proportioning. too much front brake bias. adjust the proportioning so that the rear brakes are doing a little more of the work. The opposite is also true. if the car gets loose at the turn entry under braking, the firs thing to suspect is too much rear braking bias. If you suspect this, try entering the turns without using the brakes. this will tell you if oversteer or understeer is present in the chassis without the influence of the brakes.

Push at turn transition

This is most always a stagger problem. Try increasing your stagger a little

Push under acceleration off the turn

There is most likely to much cross weight in the chassis, or too much left rear weight. However, if the car starts to push in the middle of the turn and consistently continues all the way onto the straightaway, the problem is probably not enough stagger, increase the stagger a little bit.

All of these chassis adjustments discussed above assume that all else in the chassis- springs, shocks,anti-roll bar, weight distribution, and so on....are correct already, and we are talking about fine tuning changes......

now lets look at the other extreme

Loose during entry into the turn

This is caused by either to much stagger or too much rear brake bias

Loose under power from the middle all the way off the turn

To diagnose this problem you will need to determine how excessive the oversteer is. With just a little looseness, the problems could be cured with a sway bar adjustment. Use more sway bar pre load to add more cross weight in the chassis. With a lot of oversteer, the problem is more than likely to be too much tire stagger. Go to a smaller circumference right rear tire, or a lager circumference left rear tire. Once again we are assuming that all other aspects of the chassis are correct i.e shocks, springs, alignment, weight distribution.

Loose going into a turn, pushing under acceleration coming off the turn

Like all handling problems..Root out the main cause of the problem, start by ruling out too much rear brake bias making the car loose at corner entry. Use a slightly stiffer right front spring rate to tighten up the chassis. Or a slightly softer left front spring, this will help tighten up the chassis at turn entry. The stiffer right front spring will not necessarily make the chassis tighter all the way around the track. The problem could lie in the car being loose going in and coming out and the driver is driving it in such a way that it will tighten up in the middle and coming off the turn. He could do that by taking an early apex at the corner entry. With the car consistently loose, the driver doesn't have the confidence to take the proper line and turns the steering wheel a little more to the left at turn entry. Tightening the chassis at turn entry in most cases will fix the problem at turn exit because the driver is able to drive the car on the proper line into the corner and through the middle. If the car is still tight at corner exit, there are several things you can do to loosen it up. Take out a slight amount of cross weight. Such as half a turn at the left rear. You can increase tire stagger slightly by adding a pound of air or two in the right rear tire, or by taking a pound or two of air out of the left rear tire. while you trouble shoot your problems, keep good records of the tire pressures and temperatures, This will give you a better understanding of what the chassis is doing. If you get a lot of buildup on one tire than that's telling you that your loose or pushing. More build-up than normal at the right rear is caused by pushing. Tire temperatures are a tell-tale sign of problems. Remember that this is only for fine tuning. You must have the proper springs, shocks, weight transfer before fine tuning your chassis.

Shock travel indicators

Shock travel indicators can be a good "rule of thumb" check for a chassis to see if it is handling the way it should. and if not, which end of the car to look at for the problem. When the travel of one corner is out of line in comparison to the others, it points out an immediate problem with that corner of the car. Travel indicators are a very good ballpark reference point for any type of car, regardless of weight or weight distribution, because the chassis will be adjusted accordingly to compensate for differences such as a heavier car that has heavier springs.

Good ball park figures are

Right front: 1 1/2 - 1 3/4"

Right Rear: 2 - 2 1/4"

For accuracy do not drive the car over large bumps or potholes, this will not give you an absolute readings.

Location of the shock and how the shock is mounted in a vertical plane will dictate how your travel indicator reads.

This entire section is for helping you fine tune your chassis on an asphalt track. Remember that common sense should be taken while making adjustments to your chassis. Racing is a very dangerous sport, please respect it and always use safety.