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Definitive Guide to Suspension Tuning

Intro

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 a relationship to every value you adjust and whenever you lean onto the side of performance you give up comfort in return.
Getting rid of understeer in your rear end might require you to shift some weight in your car or tune some oversteer characteristics into your setup to work out the understeer. These types of adjustments are incremental and affect every aspect of your ride. Before starting any kind of adjustments be sure to grab a small notepad and a pen to measure your suspension values before and after tuning and then you will always have an ideal baseline to work off of when tuning and can use it as a reference in case something feels off. Going forward we're going to look at some common issues and characteristics you're going to encounter on the track and what adjustments you can make to better dial in your setup to get the most out of your suspension. If you're new to the world of suspension I suggest you take a look at our Getting Started page to get familiar with what we're going to be covering in this post. Having an in-depth knowledge of your car inside and out along with all of its quirks can help you tune your suspension to it's fullest potential. You're going to be driving your car and you should be able to feel where areas for improvement are and where to look or what to say to the proper people to make those adjustments. Also knowing some basic information will be a good point to get you started in getting the most out of your suspension.
  • 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! 
Knowing these values and how your car reacts under certain conditions will help you quickly assess what settings need to be adjusted to make improvements on the track. I'm going to go over individual components and what type of feedback you can expect from making these adjustments. This is literally a feeling process and will take some time to dial everything in properly depending on your experience. Also whenever adjusting these values be sure to do so in small increments, your suspension works as a system together and making extreme adjustments potentially throws all of your previous calibrations off. 

Tuning Sway Bars

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 independently 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!

Sway Bar Tuning Cont.

Here are some common handling characteristics that can be adjusted by sway bar tuning and their effects on handling.
Understeer: If your car tends to understeer through every turn, this is because your front wheels don't have enough traction to bring the car through the turn. To alleviate this, soften your front sway bar and increase the stiffness in the rear.
Oversteer: If your car oversteers this is because your rear wheels are losing traction before your front ones, bringing the back out. To fix this soften your rear sway bar or stiffen your front. If your sway bars are set too stiff you will notice that your car handles very stiffly but without the important feedback, a driver needs to feel how the road is interacting with the car.
Having a sway bar that is too stiff in the front will result in increased tendency to oversteer when entering a corner at speed. Having a sway bar that is set too stiff in the rear will have your car wanting to understeer when exiting a corner and it will feel overall more difficult to lay your power down to the road.

Camber Tuning

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.

Camber Tuning Cont.

Too Much Negative Camber: Having too much negative camber can have some drastic effects on handling and the overall characteristics of a car. Some examples are as follows.Increased tire wear and heat build up on the inner portion of the tire.Reduced braking feel and performance in front tires due to not having a sufficient contact patch.Issues accelerating quickly in RWD cars and overall tire slippage due to a decreased contact patch.
Too Much Positive Front Camber: Usually having too much positive camber specifically on your front wheels will cause the car to begin to understeer when you begin to turn into a turn. This is because your tire tends to gain more positive camber in a turn and already having any degree of positive camber only increases that effect and in doing so that reduces the contact patch you have with the road.
Too Much Positive Rear Camber: Increased tire wear on the outer edge of the tire. Uneven heating of the tire predominantly on the outer edge, also contributing to tire wear.When entering a turn and your rear feels shaky and unstable due to the reduced contact patch.Higher chances to break grip and begin to oversteer since the tire isn't making complete contact with the road.You have more of a chance to break traction when your camber is in the extremes so be sure to look at this setting especially if you're getting uneven tire wear.

Caster Tuning

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. The 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.

Caster Tuning Cont.

Too Much Positive Caster in Front: You will find it very difficult to turn into corners at speed because the amount of positive wheel caster you have is too great. o Your wheels have a tendency to want to self-correct to center unusually hard while in a turn. o Increased road shock is also a telltale sign. If you can feel every bump in the road in your steering wheel your caster angle is too great and isn't dissipating road forces properly and should be lessened.
Too Much Negative Caster in Front o If you get very little steering response but your steering is very twitchy when turning there is a good chance your negative caster needs to be addressed and adjusted more towards the positive to provide some self-alignment to the wheels at speed and in corners. o You wheels also won't apply that correcting force you're used to because the amount of negative caster prevents them from generating any.
Uneven Caster: With uneven caster, you will get the handling characteristics of extreme caster to one wheel and a bias when turning in and out of corners. o When accelerating in a straight line you will also feel a pull to one side. This side is usually the side with the higher positive caster.

Toe Tuning

The subject and concept of toe have 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 turns 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.

Toe Tuning Cont.

Too Much Toe: - Straight lines - Too much toe in or out will cause excessive wear on your tires either on the inner edge or outer edge. Camber should be ruled out also when diagnosing tire wear. Uneven tire wear is a good indicator that your alignment settings need some adjustment. Unnecessary toe in and our settings will reduce the capabilities of your car all around from braking to accelerating and cornering, not to mention losing precious grip and eating through your tires a lot faster. 
Too Much Toe: - Cornering - Having too much toe in can feel great for initial turn in on corners but as those forces start to act on your suspension and tires more, you break traction and eventually start to understeer if your toe is too great in the front. Having too much toe in the rear causes, oversteer for the same reasons. If you find yourself oversteering on the exit of a corner the rear toe still needs to be adjusted, possibly because you need a little more to compensate for changes that are taking place on the road. 
Tuning Toe
Tuning toe and diagnosing issues during turns is a little trickier and in depth. It requires a good feel for your car and an understanding of what factors cause your car to handle a certain way.
Too much toe-in in Front o Tires have less grip o Hard turn in tendencies in corners, causes you to break traction from improperly loaded tires o More effort required to initiate turn in due to awkward angle of the wheels. •
Too Much Toe-out in Front o Too much toe out up front causes your car to drift left or right when braking. Most of the time towards the side where the toe is greater if this is the only issue. o Awkward steering wheel position that is obviously off from the direction you're traveling is another giveaway. • Too much toe in in the rear o Your rear end will feel much light due to improper traction. o Higher chance of oversteer overall, especially out of corners.  
Toe is a largely overlooked aspect when suspension tuning and as with anything else, works in conjunction with the rest of your system. Toe has a more profound effect on handling subtleties and the good and bad is only compounded by how well the rest of your suspension is performing. Toe is most affected by bump settings too so having both of these settings off could provide an undesirable ride. As your suspension undulates to keep your tires in contact with the road every variable effects how those components react. Having too great or too little of a bump (compression) setting for your shocks, springs or both with amplify the adverse effects of having improper toe. •
Too much toe-in & Bump (Front) o Increased tendency to understeer on turn in. o Sudden jerks when going over bumps due to the awkward tire angle thanks to the toe and the stiff bump settings now allowing the spring to compress. • Too Much Toe-out in Bump (Front) o More chance to understeer after the initial turn in. o Veering left or right while braking. o If a gust of wind can affect your car you've gone too far. • Too Much toe-out & Bump (Rear) o More prone to oversteer when putting down power. o Pull to one side while braking. o Jittery rear. • Too Much Toe-in in Bump (Rear) o Darting back and force on power application. o Understeer on turn in, o Instability on turn in. Too much toe in and too stiff of a rear bump setting will give you a squirrelly feeling rear end, especially when putting power down out of turns and your suspension is loaded to one side. Also you'll get more understeer and an overall sucky feeling rear end on turn in and out. Too much toe out with stiff bump and you'll oversteer in every turn because your tires are at an awkward angle and cant contour to the road to provide grip. Toe settings have a great effect on the overall handling of your car and if you're not too sure what needs to be corrected a toe setting of 0 at rest is a good place to start and you can tune from there. Toe is complicated to tune also because of how drastic the changes it can make are so be sure to be incremental.  

Center of Gravity

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 on 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 understanding 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 cause 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.

Roll Center

 CG also affects your vehicle’s dynamic roll center also. The roll center is an imaginary point which the suspension rolls around while driving and cornering, accelerating and braking. This is visualized by body roll in corners and how the front of a car dips under heavy braking. Your roll center changes under forces applied to it as you drive, the further your roll center moves away from your CG the more weight is being shifted in that direction and as stated before unnecessary forces acting on tires makes them more likely to break traction. Having a car that acts predictably past the limit of traction is a sign of an ideal suspension setup. The benefit of having independent front and rear suspension components comes with the ability to adjust front and rear roll centers on your axles respectively. Reducing weight transfer and keeping your car planted in cornering helps with improving times around the track. Knowing how your cars roll center measurements (write these down also) and how much body roll you have can be beneficial in diagnosing extreme understeer and oversteer characteristics. Having uneven roll roll centers can lead to some specific characteristics and knowing that to adjust can help work them out. When your roll center is too high in front and too low in the rear (lots of body roll in front, little in rear) your car will tend to oversteer and you will feel awkward load transfers in and out of turns. With a roll center that is too high in the rear and too low in the front you will have the opposite effect. Understeer will more commonly occur  along with the awkward suspension feel. With this type of roll center imbalance you’ll get that classic inside tire lift you see all the Honda guys riding like pros, but that’s for different reasons.

Dampening Tuning

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.

Adjustable Suspension

Most aftermarket suspension solutions provide some sort of adjustability. With dampeners, coils or shocks you can usually fine tune how the suspension reacts under different conditions, usually high and low speed along with front and rear settings come on most true race-spec suspension dampeners and coilover systems. Compression and extension motions have the ability to be adjusted on most systems. You cannot adjust how much weight the dampeners support without physically moving the weight, instead, you control how fast the dampeners react to load changes, this, of course, all being transferred to the tires and you.

Adjustable Suspension Cont.

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 the bump, high and low speed and two for rebounds, high and low speed.

Tuning Bump & Rebound

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.

Too Much Bump If you're running too much bump, there are some tell tale signs that will let you know that your suspension needs to soften up. As stated before if a pebble in the road caused a spine-jarring jolt, you need to soften up. If your car tends to jack up in corners and has a delayed response, too much bump may also be the cause. 
Too Little Bump Too little bump is just as bad as too much and causes some adverse effects. squishy steering response and lots of body roll along with nose-diving into turns are all signs that your settings are too soft.

Rebound

After bump comes rebound, or the decompression of the shock or coil back to it’s resting position. A quick note, rebound stiffness needs to be set higher than bump stiffness to make sure energy is properly dissipated when absorbing shock. Serious track bros know where to clip corners and apexes on the track and the rebound settings on your suspension greatly affect how your car reacts when hitting these spots. Having too much rebound stiffness doesn’t allow the wheel to return to it’s resting position as fast and could keep the wheel from returning into contact with the ground for much longer than anticipated if this is too high.

Rebound Tuning Too stiff of a rebound setting will not allow the wheel to properly adjust to changes in the road. Your inside cornering wheel has a tendency to lose contact with the road due to shock and then return at a much slower rate back to the road.Too little rebound or any less than your bump and your car will oscillate long after you’ve hit that bump due to energy not being absorbed properly so it dances around your suspension components. It will also be hard to keep your wheels planted and maintain traction when accelerating because there isn’t an adequate downward force being applied.

Spring Rates

Spring rates were touched on a bit at the end of the automotive springs section but will be explained a bit further here.Simply put, spring rates are calculated by the amount of force required to compress said spring one inch. You can buy springs and all of them will tell you the pre set spring rate so you can make the best decision when buying for your specific setup. This is usually measured in lbs/in. Careful consideration needs to be given when choosing your springs, whether it be a custom shock and spring assembly or coilover unit. There is no such thing as “adjustable spring rates” so unless you have lots of expendable income you better know which spring rates you need by doing google searches or checking forums relevant to your car. Some might argue that adjustable preloads are the same as spring rates but they merely move the spring perch up or down. Lower cars need higher spring rates to prevent them from bottoming out on daily driving roads because having a lower chassis means there is less suspension travel available for your shocks and springs between max bump and max rebound. Vice versa goes for higher vehicles. Having stiffer springs on a raised vehicle would feel somewhat like riding on stilts. Just a quick reminder in case you forgot. Everything in the suspension system moves and reacts in relation to the whole system and the whole goal of the system is to keep your tires maintaining constant even maximum contact with the road. As we know the whole job of suspension is to keep the wheels and tires in contact with the ground at all times, for total performance. If the spring rate is not correct, then the damper rate (bump and rebound) will not be correct, leading to even more suspension worries. That is why it is critical to adjust spring rates and then ride height setting as a way to bench mark other suspension settings. It is also important to understand that the overall spring rating of a car, should be as equally split both front and back as possible, depending on the weight distribution and drive line configuration. Otherwise we are setting the car up to either understeer or oversteer. A good rule of thumb is that for more performance oriented setups, your spring rates should equal the total weight of your car. As always you want your setup weight to be as light as possible and have that weight distributed as evenly as possible. Fun side note. For those extreme aero guys downforce needs to be calculated into choosing your spring rates. This is because as downforce increases it pushes your car down closer to the road providing precious grip but could cause your car to bottom out at speed from the downward forces from your aero pieces. Thanks to the wonders of independent suspension systems each wheel is able to react independently to changes in the road. This being said each wheel is able to support a different spring rate if necessary but ideally your spring rates should be the same on all four corners to provide a predictable ride. Having spring rates in the extremes will cause undesirable effects in your car. Too high of a spring rate and your car and your suspension will not adapt to the road to provide maximum grip. Too little spring rate and your chassis end up sitting on marshmallows and handle like a yacht. Not ideal.  Tuning Spring Rates Spring rates can vary between front and rear and have some very characteristic effects. Ideally you want equal spring rates in the front and rear to provide predictable handling. In special cases having offset spring rates can be implemented to compensate for uneven weight distribution or to bring out certain handling characteristics. Uneven spring rates that are improperly tuned will make for a very interesting ride with back and forth rocking motions that last way longer than they should because the energy bounces back and forces instead of dissipating evenly. High Front Spring Rates Front spring rates that are too high for your setup or just higher than your rear will give you understeer characteristics. High front rates and higher bump settings in general would provide a solid turn in feel but as weight transfers and the suspension has to begin adjusting to the road, the stiff springs will need a lot more force to compress and if that isn’t provided then the suspension will not adjust properly, breaking traction and causing understeer, the least fun kind of steering there is. And if you forgot the rest of the suspension system suffers from this imbalance in some way too. High Rear Spring Rates Spring rates that are too high in the rear will cause the opposite of rates that are too high in the front. You’ll get more fun oversteer but also more prone to wheel spin and that will hurt you on punching it out of corners and eat away at your tires much quicker than normal. Low Spring Rates OverallSoft spring rates are usually not the way you want to go for race setups but they are beneficial for off road applications because they allow the suspension to squish and contour to the uneven terrain. On a track at speed you might get seasick. Keep in mind lower spring rates are also affected more by downforce and you want your springs stiff enough to support the weight of your car when the air is pushing it lower to the ground. Soft spring rates will make the car very slow to react in steering inputs, and bottom out during acceleration or straights where downforce has it’s greatest effect. You’ll get lots of bouncing from the shocks from the road and lots of body roll overall.Low Front Spring Rates Lower front spring rates cause unnecessary weight and forces to act on the front wheels. This is especially apparent under heavy turning and braking. The extreme dip in the front of the car could effect braking and cause wheel spin. And getting the worst kind of steer, understeer. Low Rear  Spring Rates Squishy rear springs will cause lots of weight transfer to the rear of the car, especially apparent under acceleration. An increase in negative camber will also occur, increasing the acceleration sucking effect this setup has on your car. On the brighter side there is a bit higher tendency to oversteer because putting all of that power down will be tough for RWD cars.To wrap it all up you can unlock the full potential of your car by tuning your suspension. You can throw on all the engine mods you want but if your suspension isn’t set up to put down all that power in the right places then it’s pointless. Buying the most expensive suspension mods you can find will slightly improve your rides performance but it will prove unpredictable and uncomfortable for you and others. Every component reacts to the other to form a complicated system. Focusing on the feel of your car and knowing what characteristics you need in certain instances or how you want your car to react will get you started with tuning. Familiarize yourself with all of the variables and what affects what. This is a constant trial and error process and don’t even get me started on how big of a part tires play into this equation… but first get your suspension tuned right to get the most out of your ride. 
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