I know! There’s a ton of threads on the subject but all of them have varying answers, guesses, etc. My needs are a little bit different (or maybe not?) so I’m just looking for some thoughts.
Chassis - Italkart Supersonic - 30/32 (Think Praga Figher) with a ROK Shifter.
Use-Case - SCCA Autocross/SOLO
What I have now: Standard Height front and rear. Neutral Caster Pill, A little bit of negative camber, relatively neutral Toe. I absolutely love the way it drives. Front is responsive, the rear rotates on command if I want it to (and doesn’t if I don’t want it to)…it’s just a joy to drive (Chassis is also pretty new).
The Problem: These chassis ride really LOW (especially compared to my OTK). This really wouldn’t be too much of a problem on kart tracks but SCCA Autocross sites are a mixed bag - You never know what you might get in terms of lot quality. I have frame protectors on but I had one recent event on a pretty rough lot that wasn’t kind to the chassis.
What I want to do: I am going from middle front ride height to max front ride height (There isn’t really a in between). The rear I plan to keep at the standard position. This basically will get ride of the “rake” in the ride height. I am assuming this may lighten up the steering and maybe grip up the rear a little more. I am assuming I can combat this with some basic setup changes like track width? Is it imperative that I match the rear to the front in terms of ride height changes?
Things to note - I am aware the only way I will know is by testing. That is the plan but I want to maybe have some things to keep in mind beforehand (because I’ve never really had to play with rideheight all that much on my OTK). Setups for autocross are basically always for a green track (there is no actual track that we run on, so there is never any rubber build (except for at SOLO Nationals, if you run later in the week).
So, given that I like it’s current setup, what’s your bet on what that change is going to do based on “known chassis dynamics”.
-Not Much Of anything?
-A Drastic Change in how a drives?
-A Manageable Change in how it drives?
-Leave me alone I know what I’m doing
-Hire Newey, I heard he’s available for consultation.
If you have ballast, dropping it and the seat height down as you raise the ride height will largely negate the changes. So raise both axles an inch but drop the seat and any lead by a little more than that, depending on what fraction of your total weight is made up of ballast and human
No ballast is present or required (I am overweight for the class). Ideally, I wouldn’t have to change seat position but I understand that if things get too wonky that might be a requirement.
This depends on the chassis. With many of the shifter chassis I’ve had over the years, especially those with larger/stiffer tubing, raising the front ride height would increase responsiveness. It always seemed like a combination raising CoG and increased effective caster (there was some discussion on rake vs. caster here long ago) were the driving factors as to why it felt the way it did. Usually I’m not raising the front, but rather doing the opposite to help give the rear more traction. I recall one time in 2019 that I lowered front ride height on a TB Kart S197 (all 32mm tubing) and it turned the kart into a dump truck.
Not knowing the chassis you have, I would GUESS that if you raise the front it will be a moderate change at most. You’ll likely be able to counter the effects with front width and/or caster.
If you’re overweight for the class, and at/above ~420lbs then I wouldn’t bother getting fancy with seat position.
I was thinking more about this, and ride height should work in your favor. Unless you have blankets, your tires will also be cold. Low grip setups (like rain or cold) tend to increase the ride height, so you might have a rare win/win here between ground clearance and handling
The good news is the tire we run, the MG Green (Super Soft), comes on VERY fast. On the first run of the day it may take the tire a quarter of a run (Of let’s say, a 50-60 second course) to turn on but once it’s on, it’s on. If it’s a warm day tire blankets are not really needed as by the second run the tire will have cooled off bit, but will come up to temp really quick compared to the 1st run. Either way, we’re still fighting what the lot has to give vs. what the tire can give in terms of grip.
In any case, I think what I am going to do is just run it with the front raised and increase track front track width and see how I like it. If the steering is super sensitive, I’ll throw a 1 dot pill in it and go from there.
My setups have always been heavily reliant on track width changes. I’ll spend a bit of time setting the kart up initially but once I’m happy I just typically use track width front & rear to deal with changing conditions. To me this has been especially important as when doing Autocross, you may only get 10 minute in between each run. Ride height has almost never come into play as all of my previous karts have always just ran in the “Standard” position (according to the chassis MFR.) without issue, so for me this is “new territory”.