Suspension Optimization and Tuning Help

[Ron Sutton]

Hi Tyler,

We still have a lot of moving parts in this discussion, so I’m trying to keep them straight & in order.


In the order you need to attack them …


A big issue is the geometry not matching side to side. As I outlined earlier, this makes the dynamic geometry different on LH turns versus RH turns ... which makes the truck handle differently on LH turns versus RH turns. Your RC migrates to the left quite a bit (21") on LH turns ... and a ton (184") on right hand turns. The front roll center is too low one direction (.25" below ground level) ... and way too high (5"+) the other direction. If all other things were neutral, this would make the front end of the truck roll more on LH turns & less on RH turns. This is a significant variance and needs to be fixed first. Otherwise we’re wasting our time with the tuning.

It is not that hard to square up the measurements ... and while you're at it, make some improvements. Lance Hamilton did this to his Monte and made big gains. Read his thread on how to do this HERE.

I ran your geometry calcs a several ways and correcting it is pretty simple. It’s work … but it’s not complex. What I am going to suggest is not how I’d do it, because I would be raising all the control arm mounts significantly & building my geometry different. But that is very involved & we’re going to keep this simple.

You will want to modify & shift all of the control arm pivot points on the left side … to match the right side … which includes raising the left side ride height to match the right side. This will get all of the front end geometry performing & acting the same on left hand & right hand corners. Then use upper ball joints that are ¾” taller and it will place your roll center in a sweet spot for your high-travel/low-roll suspension strategy.

In the chart below I have the truck turning left … and made the roll angle less at 2.0° … and you can see the RC is .3” above ground. I ran the roll angle from 1.5° to 2.5° and the RC height doesn’t change much, but the migration (left & right) is less with lower roll angles.




Next, you will want to dial in the ackerman. A rule of thumb “starting point” I use often is 25° & 30°. Set your toe-out first … to 1/8” out total (1/16” each side). Do this with the steering absolutely centered. Then turn wheels either direction … until the outside tire is at 25° steering angle. Measure the steering angle of the inside wheel & let me know where it ends up. We will fine tune this number … next … with static toe-out & bump steer settings.

Before you measure & adjust bump steer, set the static camber at -0.5° & static caster at 9° on both front wheels. That is my baseline recommendation for you. Many people may tell you to run more camber or less caster, but that is not the case with a high travel front end. The challenge will be not ending up with too much camber.

Lance’s thread contains some great info on measuring bump steer where he simply clamped a straight edge & laser to the brake rotor and pointed the laser at a paper target placed a set distance ahead of the axle CL for simple math conversions. When you’re using a bump steer gauge like I and many have … you’re working with 2’ … 12” in front of the axle CL & 12” behind.



Making the laser distance 20’ from the axle CL makes the math real easy … because all you do is reduce your measurements by 10, by simply moving the decimal point. In other words if the laser shows a .300” variance 20’ away … it’s only .030” at the wheel. The farther away the target is, the bigger the variance will show. This makes it easier to see, measure & fine tune it more accurately. But most people don’t have a shop large enough to do that. So if you use 10’ simply dived by 5 … 8’ dived by 4 & so on.

For your specific goals & this truck … you will want to measure bump steer from 4” compression of your suspension to 2” of extension (at the tip of the spindle). Measure & reference everything with the spindle at ride height. Let’s consider 3” of compression your max compression travel and make this your priority point. 3” of compression is what we’ll reference in all of our conversations as “full dive.” For extension, even though you’re measuring to 2” … for track purposes, we only care about 1”. So, let’s consider 1” your full extension number for reference in discussions.

Many people think you want zero bump steer, but that’s not accurate for competition vehicles. We want bump-out in dive (suspension compression) to increase the toe-out for a higher slip angle of the inside front tire for increased grip of that inside tire. And we want the toe-out to reduce as the front end rises (suspension extension) to assist in adding forward bite/grip for corner exit.

Only as a baseline starting point, I typically find the sweet spot where I’m getting .030” of “bump-out” on each side … .060” (1/16”) total in full compression (3”). “Bump-out” is slang for toe out increasing from bump steer during compression. It is ok if you see a lot of “bump in” during dive/compression. I don’t get concerned unless it exceeds .060” each side or .120” total at 1”. I can not say what your final bump steer needs to be until I know your ackerman situation. Even then, you’ll want to fine tune this to achieve optimum front tire slip angle & grip … which can only come from track testing. I’ll guide you on “how to do this” later.

I see your Dad has already modified find your tie rod length and mounting points on the centerlink to tame the bump steer beast. You “may” find your tie rod length and mounting point on the centerlink needs to change again … and may not.

Let’s save the shock valving & panhard bar angle discussion until we have these projects on track. Then I’ll share with you the hows & why’s of modern race track shock valving. Plus I’ll show you how to tune the panhard bar for neutral handling … or to load one side more or less depending on the track.