What is your rear width out to out? Sounds like you are pretty narrow.
A flat bottom seat should always be mounted flat. It’s designed to work a certain way and putting 8mm of rake over 100-150mm is pretty drastic. Keep your leading edge the same and just tip the back up so the seat is flush with the rails.
I’d also think that at your height/weight, frame high, axle low is probably the opposite direction I’d go unless it was about 40 degrees out. Or raining. You are loading that outside rear awful hard and just may well be cooking the outside rear on a long run. Assuming your earlier in the day runs are shorter practice/qual sessions and your final session is a considerably longer final?
I’ll see how the weight distribution looks after moving the seat this weekend.
Edit: I’m skeptical 5mm will move the weight enough, maybe 10mm will. I guess I’ll move it forward a little and consider a small weight to put up front and sacrifice being a litttle over weight if its not enough.
You may be correct about the ride height, I just assumed it would be fine for 99% of the time but the track gets pretty grippy for a club track.
I am curious what others think about this too. In my experience, even a 10mm move didn’t make much difference in corner weights. It sounds like you need about 5-8% which I would guess is about 20-25 pounds more weight on the front, maybe more. So if moving the seat gets half of that what else would you have to do?
When you say the problem is worse on tight turns AND late in the day, could it be that you are counter-steering more on those? Countersteer will mechanically fight jacking and stick the rear, exacerbating the rear weight bias you already have.
Actually, here’s probably a better guess why it gets worse (other than just rubber getting laid down). I notice a significant improvement in my handling when I have a gallon or more, so that tells me I have too much rear weight. I’ve played with it quite a lot and noticed the kart starts binding when running on fumes. Do you maintain the same gas level or let it get lower throughout the day?
I used to do this on my last chassis, wrong move imo fix your weight distribution to allow for some gas in the tank. Run my Redspeed RR with plenty of gas in the tank
I guess I could just put it on the scales with a full tank and see where it’s at. I know the chassis is heavier and longer than the thinner wall tubing “4 stroke specific” karts, which makes it difficult for someone of my weight. Looks like I got some things to do this weekend.
You would have to move the seat around 3-4" to shift the weight balance from 39 up to 43% at your weight. Totally doable…
Getting you CG forward and and lower will both help your bind on exit. I have a 6-4 kid running an OTK and we have fought binding on corners consistently. We started at 43% in his first kart 18 months ago. As he continued to grow I dropped a little lead and each successive seat fit was a little further rearward. We moved from 5lbs on nose and 25lbs on seat, to 10lbs on nose and 15 lbs on seat, and then moved lead lower and more forward on seat. Checked again before TSRS SpeedSportz and we were running 41.5-42% weight, so moved to 20 lbs on the nose and 5 lbs on the front lip of seat to get him back to 43%.
I can say that he had the most free kart he has had since last November. Taller heavier guys have more challenge with the low HP classes. Making the balance change opened up our tuning window on the kart for the weekend and allowed us to do some things we typically cannot do and I could visually see the improvement in his exits relative to others on track.
