Definitive Guide to Suspension Tuning
Suspension tuning is the final step a lot of serious racers take in setting up their vehicles. You can spend all the money you possibly can on the best suspension components, and while you might notice some improvements, those parts aren’t set up to work together properly to give you the best performance and that is exactly what suspension tuning takes care of. Anytime your suspension is actively working, there is an intricate dance between all of your components going on all to achieve the same goal which is to keep your tires in contact with the road under any situation. A suspension that isn’t tuned or improperly tuned could lead to unwanted handling characteristics while driving and even more so under heavy load such as cornering. As with any suspension adjustments being made there is a give and take relationship to every value you adjust and whenever you lean onto the side of performance you give up comfort in return.
- Power to weight ratio • Engine and suspension characteristics such as RPM spikes, where your power band is, if your car has a tendency to oversteer in left turns and understeer in right turns etc.
- Handling balance and weight distribution. Have you already Corner Balanced your car?
- Tire specs and characteristics. VERY IMPORTANT
- Road and track conditions. Dry/wet, road smoothness, camber and elevation changes
- Write all of this down!
I’ve covered sway bars in a previous article and I suggest if you’re still not familiar with their function that you brush up on what a sway bar does here. Most vehicles come with stock sway bars but they aren’t adjustable, most aftermarket sway bar applications are “adjustable” sway bars meaning you can adjust them to tune this part of your suspension. Adjusting your sway bar settings can help work out some of the under and oversteer characteristics your vehicle has. Adjusting your sway bars has somewhat the same effect as adjusting your spring rates which will be covered later. One of the benefits of adjustable sway bars is that the front and rear axles of your car can have their front and rear sway settings adjusted independent to each other.This is beneficial if you want to simulate a little more stiffness or soften up the front or the rear individually. As with most suspension settings, setting them to a stiffer setting will decrease body roll and softer settings will increase body roll, the more you tune towards performance the less comfort you get. Keep in mind this is a feeling process and stiffest doesn’t always mean best so play around with your settings to find one that suits your style. Having too stiff of a sway bar setting on your car could lead to the inside wheel in a turn lifting off of the ground, the literal opposite of providing traction, so that is to be avoided if possible. Also having stiffer settings here only further transfers any other suspension issues to your components so be aware of all of the variables!
As with sway bars, camber caster and toe have been covered extensively on another page so if you aren’t familiar I suggest you brush up before diving in. Camber angle is a very important value to consider in suspension tuning as it has the most effect on your contact patch with the road and the more contact you have, the more grip you have. While driving it is likely your suspension will pass through various degrees of negative, positive and no camber in adjustment to the road, this is normal. Where camber adjustments come into play is during hard cornering and acceleration. As stated in the camber section, the inside tire during a turn usually experiences some type of positive camber forces, rolling the top of the tire outward. If this camber gain isn’t adjusted for then you are losing precious bits of grip on your inside tire while turning because the inside tire has a tendency to camber towards the positive under cornering forces. A couple of degrees of negative camber proves effective for compensating for the tendency for your inside wheels to camber outwards, those precious degrees of negative camber negate the tire from cambering towards the positive. A properly set up vehicle has some negative camber at rest and under heavy cornering the camber adjusts itself from a negative back to zero to counteract the positive camber forces acting on the outside of the tire.
Caster angle, depending on whether it is at a positive or negative angle, determines the amount of self correction the wheel does under load along with the overall steering responsiveness of a car. Too much positive caster makes the front of the car more prone to oversteer and too much negative caster gives the opposite effect. Improper or uneven adjustment of caster also leads to a lot more input and effort needed when steering your car in and out of turns. As with any other adjustable suspension component, make small adjustments to this because everything works in a system and is affected by these changes. Check out our Caster section to get a better idea of how caster affects handling.
The subject and concept of toe has already been covered here so feel free to brush up if you need to. In short, toe determines whether your tires are pointing outward or inward like your feet would look if you were to touch your toes or your heels together. This setting has a huge effect on tire wear, handling on both turn in and in straights. Toe, or tracking as some call it can be felt if the car pulls to one side while braking heavily or if you let go of the wheel and you start to feel your car pull to one side.
The center of gravity (CG) can be seen as the balancing point of the car, if you hung a car from a cable above the ground it would be balanced perfectly. This is seen as the true center point of a car and all weight shifts and suspension changes travel through the center of gravity. Center of gravity is so important suspension systems are designed around it. This is because it is very hard to change the CG once the car is built unless you built the car yourself and even then your choices are based around it. All forces that act on your vehicle and suspension travel through the CG so it is crucial that you have a good understanding of it and how it works to further educate you on the characteristics of your car. Most people believe that lower is better and in most cases that is true ,but lowest isn’t always best. Either way a good understand of CG is necessary to master suspension tuning. Lower center of gravity means less weight transfer takes place, this is beneficial for the tires to retain grip because the sudden added weight in a turn from a high CG can caused the tires to break traction or even worse, a rollover. Less unnecessary stress on the tires and suspension means they can do their job better and provide you with maximum grip as opposed to fighting the forces trying to get it to break traction.
Dampeners AKA shocks, work in conjunction with your springs to complete the foundation of the car’s suspension system. Without dampeners and just springs, a car would take forever to stop bouncing on only it’s springs because it would take a lot of time for that energy to dissipate. Dampeners dissipate that extra energy on compression and rebound strokes in a suspension. Imagine trying to race with a constant bounce that only gets worse and never goes away with any turn. No thank you.Dampeners not only help dissipate shock and vertical travel induced by the road but with their constant downward pressure on the wheels to stick to the road, dampeners help maintain contact with the road at all times by providing a constant downward force thanks to also supporting the weight of the car. The amount of force that they are able to apply is affected by, you guessed it, everything.
1 Way Adjustable Suspension Usually 1 way suspension setups have adjustments for rebound only, or the outward motion after compression.
2 Way Adjustable Suspension Two way adjustable suspensions offer the ability to adjust not only rebound but also bump, AKA compression settings also. Most mid range shock and coilover systems come as 2 way systems
4 Way Adjustable Suspension 4 way systems are reserved mostly for race applications and offer 4 way adjustability by further breaking down rebound and bump settings to be tailored for high and low speed giving you a total of 4 adjustments. 2 for bump, high and low speed and two for rebounds, high and low speed.
Bump: During bump, or compression, the dampers and springs absorb the upward forces from the road whether it be weight shifting from entering a corner or a literal bump in the road. After bump comes rebound. When all of the energy from the road isn’t able to be dissipated for whatever reason, after bump and compression the cycle starts over until all of the energy is gone. Bump settings not only need to be adjusted to deal with road conditions, braking force, acceleration and cornering, but also elevation and uneven surfaces. Too stiff of a bump setting and you might as well just be running solid metal rods in your suspension. Your suspension will be too still to absorb any shock from the road and it all gets transferred to the cabin and the poor victims of discomfort inside. Going to the extreme on your bump settings in either direction is never good for handling and like everything else should be adjusted incrementally.