corner entry push

[Richard Hudgins]

John,

I agree most heartedly with your statements above.

As to what I would recommend for a basic setup process for the typical Cobra follows: (Please Note: this leaves out camber curves, Spring rate changes, anti-roll bars, etc. We assume that these settings cannot be changed at the test session due to lack of tools, parts, etc.)

1. Find a skid pad or like area where one can drive the car in steady state. At least 200 foot radii if possible.

2. Unhook anti-roll bars and set dampers to the softest settings possible. Set tire pressures to lowest recommended settings. Check static cambers all around. Chalk tires inner and outer edges 1 inch up sidewall and 2 inches into tread. Write everything down!!!!!!!!!

3. Drive car around skid pad at a medium speed (No sliding) in the highest gear possible to establish driving technique. (It is very important not to over drive the chassis) Do 10 or so laps to bring tires up to temp. Check tire pressures. Check tire roll by examining the chalk. (If you have a pyrometer, check temps. This is the best way to establish minimum tire pressures.) If too much/too little tire roll adjust pressures. WRITE EVERY THING DOWN!!!!!!

4. Again drive around the pad, but this time progressively increase speed until the car will no longer maintain the arc. (Important!! Time the laps.) At this point you will discover whether you have understeer or oversteer as a basic characteristic of the chassis. You also know what lap time the car will produce with the current settings. Check hot tire pressures and look at the chalk. (Once again, if you have to much/too little tire roll adjust pressures.) If tire contact looks good, go to next step.

5. Now we are going adjust tire pressures to see if a "Neutral" chassis can be achieved with pressures alone. (Note: 1 psi tire pressure is equal to aprox. 50>75 lbs wheel rate.) Adjust pressures up in 1 pound increments on the end that is sliding first. Drive around pad until car will no longer hold the arc. (TIME THE LAPS.) What change did the tire pressure make in the balance? Keep adjusting and testing until the chassis is neutral. At this point, examine your data. What is the tire pressure differential front to rear. (If it is more than 4 lbs. your spring rates need changing. The tire pressure differentials will tell you approximately what spring rates changes are needed.) Check the times. Are you quicker? If you are not, you are overdriving the car, either with throttle input or steering input.

6. Now hook up your anti-roll bars and do the whole thing again. The car will feel much better due to lack of roll. TIME YOUR LAPS!!! Adjust tire pressures until the car is neutral. If the tire pressures are more then 4 psi differential, your bars need resizing. (Or adjusting if so equipped) Are you quicker?

Now comes the tricky bit. Dampers. You can use the skid pad to start the adjustment process, but setup of dampers is really track and surface dependant, but the pad will get you started.

1. Mark off a entry point onto the skid pad and a exit point. (You will want a run up area that allows you to reach the speed that you were attaining in the previous tests.) Leave the dampers set soft.

2. Treat the skid pad like a 90 degree corner that you do not have to brake for. Accelerate to the turn in point and pick up the radius of the skid pad and follow it to the exit point. (Have someone time you between these points) What did the chassis do? Did it initially understeer? Oversteer? Was the transition too fast or feel abrupt.

This is one adjustment that your are going to have to do by feel. The best thing to do is to change the damper settings in stages. Front bump harder, Test. Rear Bump harder test. Front rebound harder, test. etc. etc. When the chassis feels good to you in its turn in and exit transitions, check your times. Are you quicker? Add in braking on the entrance. Adjust as required.

OK. Now that you have done all of this, you should have a chassis that you can take to the track and at least be able to get around with some confidence.

Now, you can start the real chassis development and spending contest.