Handling 101, FAQ, FFR FAQ

Handling 101

How to Adjust Your Handling
By: Bill Peirce

Disclaimer: You should only test handling changes in a safe, closed area. Don't make mechanical changes unless you are sure they will work. Always check your work to make sure everything is tightened. Read the rest of the disclaimers. If you don't agree with something discussed, email me your comments.

Definitions: Study these so you know what we're talking about.

Understeer = Also called push or plowing. This means your car goes doesn't turn where you point the wheel and you have to use more steering input to get the car to turn. This means the front tires are losing traction. A car can have oversteer entering a corner under braking, in the corner with or without throttle input and exiting a corner under acceleration. It is the opinion of most racers that Understeer is safer, but it also slower.

Oversteer = Also called lose. When you have oversteer, the rear end wants to step out or even slid out from behind. This can happen when exiting a corner or even when entering a corner under braking. When the car kicks out during braking or when releasing the gas pedal, this is also called trail throttle oversteer or trail braking. While this happens the most in rear engine or mid-engine cars, it can also happen in short wheel base front-engine cars with good balance. Trail throttle oversteer is a helpful thing to learn because it will "rotate" the car around tight corners. But it's hard to learn and requires a lot of practice. The difference between executing a nice rotation and spinning the car is a very small envelope. Excessive Oversteer can be dangerous, but it usually considered faster by most racers.

Neutral Set-up = A car that is totally neutral can be a thing of beauty to drive and is what we should all be striving to achieve. It means the car will 4 wheel drift through a corner without oversteer or understeer. Not that 4-wheel drifting is the fastest way around the track, because its not. Neutral means your car will neither push or oversteer.

Rule #1: Benchmark your car before making changes. A good place to work on your cars set-up is during an autocross event. This way you can make the changes and see if you improved your times. Another way is to use a G-tech or similar instrument to measure the G-forces. The least effective way is to make changes based on the seat of your pants. Because what "feels" fast is often not the fastest way around a course.

Rule #2: Only make one change at a time. I know this is hard to do, but you have to discipline yourself into only changing one thing at a time before trying something else. Why is this important? For one, your changes may negate one another. Second, the only way you're going to know what works the best on your car is to try each adjustment and see how much it helps or hurts without anything else changing.

Rule #3: Keep a good log book. If you're serious about your handling, you will be trying many different things that will be hard to keep track of.

Rule #4: Every action will have the opposite reaction. For instance, if your car pushes during slow speed corners and you make a change to decrease this push, you will increase your over-steer by an equal amount. However, you may never notice the opposite change because it makes your car more neutral.

Rule #5: Use the following chart to change the handling of your car. Try the easiest things first. Like tire pressure or ride height.

OVERSTEER / UNDERSTEER CORRECTIONS

Understeer Corrections		Oversteer Corrections.
Push, plowing, front tires slide out first.		Loose, rear tires slide out first.
Usually slight understeer is safer.		Oversteer can be dangerous, especially at high speeds.
Raise front tire pressure.		Lower front tire pressure.
Lower rear tire pressure.		Raise rear tire pressure.
Soften front shocks. Stiffen Bump.		Stiffen front shocks.
Stiffen rear shocks.		Soften rear shocks.
Lower front end.		Raise front end.
Raise rear end.		Lower rear end.
Widen front track.		Reduce rear track.
Install shorter front tires.		Install taller front tires.
Install taller rear tires.		Install shorter rear tires.
Install wider front tires.		Install narrower front tires.
Install narrower rear tires.		Install wider rear tires.
Soften front sway bar.		Stiffen front sway bar.
Stiffen rear sway bar.		Soften rear sway bar.
More front toe out.		More front toe in.
Reduce rear toe in slightly.		Increase rear toe in.
Increase front negative camber.		Reduce front negative camber.
Increase positive caster.		Reduce positive caster.
Soften front springs.		Stiffen front springs.
Stiffen rear springs.		Soften rear springs.
May need more front suspension travel.		May need more rear suspension travel.
Install wider front wheels.		Install wider rear wheels.
Use softer front compound if possible.		Use harder front compound if possible.
Use harder rear compound if possible.		Use softer rear compound if possible.
Remove weight from front of vehicle.		Add weight to front of vehicle.
Add weight to rear of vehicle.		Remove weight from rear of vehicle.
Drive a different line.		Driver may be going in too deep.
Use weight transfer to your advantage.		Driver may be getting on the throttle to early.
High Speed. Increase front wing downforce.		High Speed. Increase rear wing downforce.
Too much front brake.		Too much rear brake.
Vehicle is TWITCHY at limit and hard to keep		Vehicle slides and is easy to drive at limit but
ahead of in the steering department.		does not corner to full potential.
Lower front and rear tire pressures slightly.		Raise front and rear tire pressures slightly.
Suspension may be too stiff.		Suspension may be too soft.
Shocks may be set too firm.		Shocks may be too soft.
Tires may be old or hard.		Roll centers may be too high.
Vehicle may not have enough suspension travel.		Lower vehicle.
Vehicle may have a toe problem front or rear.		Tires may be too hard.
Increase negative camber front and rear if possible.		Widen track front & rear.
A properly set up vehicle will usually push slightly on corner entry, be fairly neutral at the apex (STEADY STATE) and exhibit slight power oversteer on corner exit. Tight courses may require more oversteer and fast tracks more understeer. Items needed: Accurate tire pyrometer, tire gauge, notebook and tape measure. Suspension information books. Note: This is a sample of the methods used to correct various handling problems. Books have been written on this subject. Not every correction will always work as expected. Stiffer front sway bars will, in many cases, decrease understeer because of reduced body roll and better camber control. The best rule is to change only one thing at a time and keep notes. Follow these suggestions at your own risk, we listed them to make your racing safer and your road car safer.

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