A Guide to Track and Race Car Chassis Setup – including Setup Tips Posted on 19 Apr 2021Given the range of adjustments that can be made to a track or race car, to find that sweet spot of optimum performance, handling, and reliability, it can be difficult to know where to start. Vehicle setups are variable for a variety of reasons, ranging from weather, driver preference and racetrack characteristics. Start with our guide and tips below.What is Oversteer?Oversteer is where the front of the car turns as directed by the driver via steering input, however the rear of the car will want to travel along its original trajectory, often described as the rear trying to overtake the front. The rear of the car will lose traction, brake away and in extreme cases induce a spin. What is Understeer?Understeer is where the front of the car pushes onward closer to the trajectory the car was originally traveling rather than where the wheels point. Some describe it as the front washing out. Steering inputs must increase, and the driver will notice less nervous behaviour from the car. What does an Anti-Roll bar (ARB) do?As a car turns, the cornering forces cause the car to roll away from the inside to the outside of the corner. The amount of the roll needs to be controlled in order to keep the contact patch and the camber of the tyres at their most effective. The job of the anti-roll bar is to adjust the understeer to oversteer balance of the car during cornering, which it does by altering the load that transfers to the outside tyres at the front versus the rear. A stiffer anti-roll bar will increase the load on the outside tyre on that axle. If both bars are made stiffer by the same amount, the load transferred will remain the same, but overall chassis roll will be reduced, which may require a camber adjustment. What is the benefit of an Anti-roll bar?Some cars only have a front anti-roll bar, and on some cars, the rear bar can be disconnected. This allows you to tune your damper and springs with less compromise from body roll. Some cars have no anti-roll bars at all, in which case any tuning of roll stiffness must be done with shock/spring adjustments. The downside to this is that you are trying to control roll, ride and traction with only one method of adjustment. For example, a bumpy, rough surface will favour a softer spring, however our lack of roll bar means you will require a stiffer spring. Running stiffer roll bars and softer springs will lessen roll, while maintaining good tyre contact on poorer surfaces. Should I fit a Front Anti-Roll Bar?Stiffer Front Anti-Roll Bar: Will increase overall car stability and move the cars balance toward UNDERsteer. The compromise can be on bumps and/or braking. A stiffer front bar will reduce compliance, so when one tyre hits a bump the entire front axle will be affected through a loss of overall grip. Softer Front Anti-Roll Bar: Will shift the cars balance towards OVERsteer (or less understeer). The front will improve in compliance, which improves performance in brake zones and over bumps. A mild oversteer can also improve corner exit and require less steering input from the driver.Should I fit a Rear Anti-Roll Bar?Stiffer Rear Anti-Roll Bar: As you accelerate through the corner while the steering wheel is still turned, the rear ARB becomes very effective. Running a stiffer rear anti roll bar supports the rear and shifts balance to less UNDERsteer at the corner exit. Again, the compromise is in compliance; If the roll bar is too stiff, you run the risk of snap oversteer ultimately compromising your corner entirely.Softer Rear Anti-Roll Bar: Allows more roll at the back of the car, which will be most evident at corner exit. If the bar is too soft, the car will exhibit gradual exit OVERsteer. How much Caster should I have?Caster is an alignment measurement on the front suspension that relates the tyre contact patches to the steering axis. As caster increases, the forces attempting to straighten the steering wheel will increase.Caster adjustments are often made at the top mount in a forward and backward motion. Caster changes are best used to adjust the amount of steering feedback the driver wants to feel. If a car has very little caster the steering will feel dead and require more input. Increasing positive caster helps centre the wheel on corner exit. But go too far and the car becomes unstable at corner exit or all the way through high-speed corners. The amount of caster you run will vary from car to car and from driver feedback. Some cars already have increased caster on their sportier models via different under body geometry and arms, top mounts, or in some cases entirely different strut towers. Caster also affects Camber so remember to set caster first then camber. How much Camber should I have?Camber change is an adjustment intended to ensure the tyres contact patch is as large as possible at maximum loads. This occurs mid corner when body roll will put the outer wheels under the most load.Front: If more mid corner grip is needed, adding negative camber to the front of the car should help. However, the compromise is a smaller contact patch in a straight line, and therefore less performance/grip is available for braking, resulting in a tendency to lock up sooner with less pedal pressure. Under acceleration where there is less tyre on the surface to put the traction down. Too much negative camber can also cause snap understeer, where the car doesn’t roll to the contact patch and the car doesn’t turn. Rear: Adding negative camber should also increase rear mid corner grip. The compromise in the rear is that too much negative camber may cause snap exit oversteer and excessive tyre wear as the contact patch is smaller and more focused. Camber effects toe, so be sure to set camber before toe. Toe does not affect camber. Should I change my gear ratio?The top speed of a car and its acceleration can be changed by changing gear ratios. Individual gears can be changed and more commonly the final drive. For a car to accelerate quicker, get off the line faster and move quicker, you’ll need low (short) gears.If you want your car to reach a high top-end speed, you’ll need high (tall) gears. The trade off with changing gear ratio is that as a gear has a longer range, it takes more time to move through that range. In final drives, a taller final drive will make the car feel slower through the gears but will ultimately allow a higher speed. Conversely a car that’s quick through the gears will be limited by a lower top speed. In terms of the number an example would be that a 4.4 may be standard final drive, a 5.1 would be a quick ratio, and a 3.5 would give you high speed. In racing terms, the optimum is to have the individual gears suited to the style of track, a tall first is common, while having the top gear just about to limit the car just at the end of the longest straight allowing the whole gearbox to be used. Sometimes the car will be on the limiter for a very short time as a compromise, for a benefit elsewhere on the circuit. Losing a couple of hundredths there but picking up several hundredths elsewhere may be favourable. Perhaps the car will only hit the limit with the least amount of fuel etc. How low should I set my ride height?Ride height changes have a massive impact on a car’s behaviour. There are a few things that you want to be aware of when going for the optimum ride height. What looks good isn’t always something that is going to work well. Take into account the stroke available on your damper. Lower too far and you can run out of stroke leaving you on the bump stop. Check your lower arms for the angle they sit at when the car is low. Too far out of its optimum range and you will need to look at roll centre correction. Often when looking to lower a car for looks the car is set level. However, for performance you may run the car with Rake. This is when the car is higher on one axle than the other. When the front suspension is set lower than the rear, the car is said to have “Positive Rake” and vice versa. Front: lowering the ride height of the front of the car will shift weight balance to front, increasing front tyre grip for less understeer, more oversteer.Raising the ride height of the front will shift weight balance to the rear, increasing the grip of the tyres at the rear for more understeer.Rear: lowering the ride height at the rear of the car will shift the weight to the rear for understeer.Raising the ride height at the rear of the car will shift the weight to the front of the car for oversteer.Ride height effects camber and toe, so be sure to set ride hight before toe. Toe does not impact ride height. Should I change Tyre pressures on a track day?Tyre pressure should be determined by the load you put on them. The more load the more pressure. So, a heavier car, or a banked turn, or suspension compression, more grip will be retained with higher pressures, whereas with light loads, lower pressures tend to give better grip.On the circuit you will generate a lot more heat in the tyre. Heating the air in the tyre will increase the pressure. Lowering the tyre pressure is necessary so that once the pressure in the tyre increases with the heat, it’s back to its normal operating temperature, giving optimum performance. Running your road tyre pressures on a track day will very quickly degrade the tyre. The difference between running all day, and only lasting one session. Raising tyre pressures will in reinforce the sidewall of the tyre, which makes the tyre more responsive to the driver’s inputs, particularly during the initial turn-in for a corner. The compromise is that as the tyre stiffer if will start to lose compliance with the road. Losing that compliance will induce slip from the tyres. lowering tyre pressures will allow the sidewall to move. As the tyre softens, the compliance improves and, generally, grip improves. The downside is that the car will become less responsive to the driver inputs as the tyre absorbs that initial input. Do I need to change my wheel alignment for track?Toe is an alignment setting that represents the direction the wheels are pointed in relation to the centre line of the car. If the wheels are PARALLEL, it is at zero toe or neutral. If, for example, both front tyres are pointing inward towards the centre line, they then have positive (+) TOE or TOE IN. Negative (-) TOE or TOE OUT is the opposite.Front Toe: This is a powerful tool to tune how the car behaves in a straight line and corner entry.Toe In (+): Should increase stability in the braking zones and slow down the response in the initial turn of the wheel. The compromise is an increase in scrub that will reduce straight line speed. Sometime people will refer to this as driving with the brakes on!Toe Out (-): will have the largest effect at corner entry by speeding up the car’s response to the initial turn of the wheel. The trade-off can be straight line speed and stability. Rear Toe: This adjustment affects the general feel and behaviour of the rear throughout the corner. Some cars do not have this facility.Toe In (+): on the outside loaded tyre will help rear grip and overall stability.Toe Out (-): is usually added to reduce significant levels of understeer that can’t be reduced by other methods. What spring rate should I go for?The springs are what hold the car off the ground! Quite literally, every bit of feedback that a driver senses from the road surface comes through the springs. Changing the springs on the car is one of the most powerful tools available. The natural choice is to stiffen the car significantly. However, it’s not always the way to a fast car. It’s easy to over spring a car, for a “race” feel that makes the car nervous, difficult to drive and ultimately not as quick. This is also reflected in comfort. If your car is a road car that you use on track a compromise must be made between ride quality and overall lap time. Front: Stiffer: Stabilises the car and shifts the handling balance toward understeer. The compromise is less compliance. Softer: Adds a significant amount of front grip. The compromise is a less stable car.Rear:Stiffer: Reduces understeer, particularly at mid corner and exit. The compromise is less compliance in the rear and less grip.Softer: Adds rear grip and shifts the balance toward understeer.