At the race I was at last weekend, I moved some of my ballast weight from the rear of the seat to the front area, just past the torsion bar. Instantly, the “oversteer” I had felt before was gone, kart was much more planted and I gained 0.8s a lap. (43.2 vs a 44.0) What I don’t understand was how? Track usually loses grip from practice to the race (not sure why either) and all the advice I’ve been given on where to put weight has been put more weight rearward if you want less oversteer, more forward if you want more oversteer.
Could someone explain this weight-distribution magic? Or was this improvement caused by something else potentially?
Chassis is a 401R with LO206, OTK Seat, baseline setup, and Evinco Blue tyres.
Here is where tire load sensitivity comes in again. During pure cornering, moving weight rearward creates more relative grip in the front and increases oversteer. Moving weight forward gives more relative grip in the rear and increases understeer. Race Kart Setup Guide #2 - Center of Gravity
The kart rotates through weight transfer. More weight on the seat can simulate a taller driver and help the kart ‘tip’ better and make it want to rotate more. Moving that weight to the front reduces the weight transfer you’re getting in the seat, so it can settle the rear of the kart down as less of that weight is swinging around on the rear of the kart.
It all depends on where you are in the tuning window. Do you know your weight distribution percentages prior and after the weight move? If you were outside of the normal window of weight distribution, it’s very possible to see unusual results from a tuning change.
This is why having a very neutral baseline setup with a seat placement close to the factory recommendations is important, because if you stray too far from the box and where the kart should be set up to start, tuning becomes a real challenge as chassis adjustments start to have unusual effects and get confusing for the less experienced driver/tuner. I honestly think that is where a LOT of the “kart tuning is voodoo” stuff gets thrown around. If you don’t start from a sound foundation of set on the kart, adjustments can have the opposite effect of their intent, because you’re really outside the window where the kart works.
Typically less front weight is going to provide a more numb front end and generally increase understeer. But the opposite can happen if you are not in the right place to start.
Early on experiencing oversteer. What was really happening was I was understeering, then front would catch, then snap oversteer. Is it possible something like that was happening? Then moving weight forward improved turn in and cured snap oversteer?
I don’t have access to scales right now, so not sure on previous weight distribution before or currently. Just making changes based on some bathroom scales I used one time.
Maybe? I’m very new to karting and I haven’t developed a feel for exactly whats happening on the kart yet so very possible that was happening and I couldn’t tell.
I have an app on my phone called iRaceWeigh. I was able to get it from the app store for my iphone. If you remember your weights from before you can plug those in and then if you remember how much weight you moved to the front of the kart you can change your front weights on the app and get an estimate of what your new percentages are
I still remember that from 20 years. I kept trying to reduce turn in and the back kept stepping out more. I do not remember when I had the aha moment. Since then I try to make sure I am focusing on what happens at the start of the corner