Suspension Tuning Guide
Be it in sim racing or real World racing, suspension tuning has always been a black art of sorts. The fundamentals are the same from real car to sim racing. Everyone understands the basics of making more power which yes, does make you faster but a proper handling car is much more important than power because no matter how much power you have, if you can transfer that power to the ground in a efficient way, no amount of power is going to help you win a race. While this article could be a hundred pages long we have broken it down in a quick and easy way. Below is direct off the Cheat Sheet that we have used for almost three decades at the track, be it autocross, rally or road racing.
Sway Bars
Understeer – Reduce front or/and increase rear sway bar Oversteer – Increase front or/and reduce rear sway bar
Camber
Negative Camber – Increases cornering grip. To much camber will wear tires faster & reduce braking capacity.
Neutral Camber – Maximum braking and acceleration
Positive Camber – Not relevant in road/circuit racing
Toe
To Much Front Toe-In – Car understeers mid corner, unpredictable under braking.
To Much Front Toe-Out - Unstable in straight line, unpredictable under braking.
To Much Rear To-In – Oversteer on corner entry, rear feels light and unstable.
Low Rear Toe-In – Oversteer on corner exit when accelerating (power oversteer.
Caster
Always make the same adjust right and left, not being equal will create instability.
To much caster increases steering effort and road vibration. To little caster will make the twitchy and have a lack of feeling and response.
Ride Height
Low is not always better! Low ride height reduces weight transfer and helps handling. To low will create bump steer and reduces suspension travel. Travel is needed for curb hoping, elevation changes, etc. Never go to low! The rear should always be a little higher than the front. This works as added downforce.
Shock/Spring Stiffness
Stiff Front – Increases rear grip, increases understeer.
Stiff Rear – Increases front grip, increases oversteer.
To Stiff – Harsh, rough ride hard to get traction out of corners.
To Stiff in the Front – Unstable braking
To Stiff in the Rear – Wheel spin and oversteer exiting corners.
To Soft – Floating and unresponsive
To Soft Front – Increased body roll, car will understeer exiting corners.
To Soft Rear – Oversteer when applying throttle and squatting on acceleration.
Bump & Rebound
Front Bump Increase – Increases Understeer
Front Bump Decrease – More Oversteer
Rear Bump Increase – More Oversteer
Rear Bump Decrease – More Understeer Front
Rebound Increase – Increases Understeer Front Rebound Decrease – Increases Oversteer
Rear Rebound Increase – Increases Oversteer
Rear Rebound Decrease – Increases Understeer.
Tire Pressure
Alright, tire pressure is more important than almost any suspension change/setting, it is also free! Changing tire pressures can increase oversteer, understeer and traction. First things first, there is no reason to ever run a low tire pressure, at least in racing, there are reason in off road trails, sand, crawling but we for racing there is no place for low tire pressures! Start with the recommended pressure (you can find the recommended pressure on the side of your tire), now add 4 pounds to each tire. Take a piece of chalk and mark two tread blocks on each tire. Start on top of the block that should contact the ground when it rolls and run a chalk like over the edge/shoulder to the little triangle on the sidewall. These triangles indicate where the tread ply ends. Take a test run and examine the chalk line, this will tell you how much the tire is rolling over. How much of the lines are gone? If you are passing the end of the line or the triangle, add more pressure! Some roll over is fine but if you exceed the limits and pass the triangle you are loosing traction, loosing time and damaging the tire. To little pressure is kind of like a soft suspension. Proper tire pressure in the front tires is essential but the rear tires is where it gets tricky and has big effect. Once you have determined the proper pressure you can adjust to increase oversteer or understeer. Adding pressure to the rear tires thus reducing the contact patch will increase oversteer, if you want increase understeer, reduce tire pressure in the rear.
Tune as you will! There is no perfect setting for a single car, what set-up works for one person may not work for another.
Looking for the best parts, there is always one rule; Use companies that actually race the product they make!
Suspension Resources
Biltsein-Shocks
BC Racing-Coilovers
H&R - All things suspension
https://hrsprings.com/products
Longacre - Suspension tuning tools https://longacreracing.com/
Demon Tweeks- Everything in one place