OTK handling question - front/rear weight

hey guys!

I have heard with OTK the front/rear recommended weight distribution is 41-43% on the front if have the kart on some scales.

my question is if I set the kart up to have more weight on the front end does that increase front end grip or reduce it? I’m still learning the black art of kart tuning and wondering what the impact would be if I have more or less weight on the front tires on the scale

thanks!

My experience with the OTK is that weight distribution is important. It’s good the get the kart to handle properly with the neutral settings on reasonable grippy track by weight distribution. If the kart pushes excessively, I’d move the weight forward. For whatever reason, I always run the seat more forward than recommended. I’m short and light and have to run 50# of lead to make weight, so that might be why.

There’s no concrete answer to that. Higher front weight will make the steering heavier but reduce the amount of weight on the seat area of the kart, which is how you generate flex and sidebite and inside rear wheel lift. So while it might make the front feel “grippier”, it might also deter the rear from releasing the inside rear wheel and make the kart flatter.

But it depends where you are in the window of tuning. A kart can react differently depending on so many variables, you can’t tune it in your shop.

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Baseline setup for an OTK in a TaG class gives 43% front weight.

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this 100% go to the track and test

huh thanks guys. the more i learn about karts the more wacky they seem to me hahah

so for a rear brake only 80 shifter on evinco blue tires racing at 375lbs what would you set the kart up as a baseline for front/rear weight on a scale? sounds like 43% is good starting point and then tune it at the track from there?

I will say at the last race, it was super cold out like 50* but i had to put max caster in the kart and damn near max front width to get it to turn in the way I wanted which is part of why I’m going to put the kart on a scale just to see if somehow the weight is way off somehow

thanks, yeah I used to run the kart at 395lbs with front brakes and a 20lb weight in the crotch and in our local class you can run 375lbs with rear only brakes and since I switched to that the kart really does not turn in like I’m used to, it’s only two races for me with kart rear only brakes at 375lbs weight and it is a somewhat different driving style so I’m still getting use to that but reason I want to scale the kart is see if somehow my front/rear weight is way off somehow just to reality check myself

43 is a great starting point. If you can’t make the kart work via other adjustments at 43 then start to move the seat around some.

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Start in the 41-43 range, exhaust all your tuning options, then move the seat if need-be.

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thanks everyone, will get some bathroom scales and see where the kart is and adjust it to 43% if it’s way off

do you guys view having max caster in the kart and simultaneously max front width necessary to get the kart to turn in ok to be a symptom of an issue? It feels extreme in 50-55* weather to need that much action in the front at max settings but I’m still new to this kart tuning game

thanks Larry, have you ever scaled your kart with you in it and the seat at your forward setting? Ultimately whatever makes the kart work and go fast but I’m curious if you are >43% on the front tires

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Yes, that’s definitely a sign of a too-heavy rear. How’s your braking technique? TonyKarts understeer if you don’t turn on the brake.

I’m only in season 2.5 of racing local club stuff so still a lot to learn but I typically brake as hard as I can and then release and turn in, which worked great with front brake shifter kart but now that I am on rear brake only it feels like I need to brake hard as I can and then give the brake pedal a final nudge at same time as turning in to free up the rear a touch or something. still adjusting my driving style but since I swapped to rear brake only the kart turn in has been dramatically worse which has been a surprise.

so you’re saying in your OTK that you trail brake a touch to rotate the kart? super interesting. I always was told that trail braking in a kart is not optimal driving technique like 90% of the time so I try to minimize that most of the time

Trail braking is necessary to offset the understeer into slow corners to be able to have a kart that gives a neutral balance in faster corners. If you don’t brake hard enough the kart will understeer much worse with the rear brake than with front brakes simply because you won’t transfer as much weight off the inside rear wheel.

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You shouldn’t need max front width and full caster to get the kart to work under normal circumstances.

And trailbraking is very useful in certain situations, with most top drivers trailbraking throughout the lap. My video on braking goes pretty in-depth in specifics:

But let’s sort out the weight balance first before we start throwing brake technique into the mix. Straight-line braking is fine for now.

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Mike I don’t know. I used to scale but I don’t anymore, so I don’t know my weight distribution. All I know is I start at 1 or 2 cm forward of the OTK recommendation (because of experience with the OTK) and if needed I move the seat when I’m at track.

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Whether you trail brake or straight line brake, typically turn-in is not a problem with an OTK. That is if the chassis is set up neutral, straight, seat position is correct and there are no cracks in the chassis and the track has some grip. The OTK is really forgiving on setup to get close.

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Thanks everyone! Let me scale this thing and see how that looks and circle back.

Really interesting on trailbraking also and makes sense front brakes vs rear only. I have historically tried to minimize trailbraking but i think i need to change my technique here also

Love your videos! Super helpful

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