I recently sold my old junior kart and bought a senior kart a while ago. It is a 401s racer TonyKart with a restricted Rotax 125. When i was in juniors, i never had any issues with kart movement under braking, it has been a few years since i stopped go karting, and recently got back into it, but i remember how to kart and everything but the kart is incredibly unhappy under braking. when i come up to a corner and try and break the kart just tosses around ruining lap times. is there anything it could be thats doing this, i dont know why its doing it while i am very patient with braking.
Are you able to get video of it? It’d be super helpful to see exactly what’s happening.
Two things cause instability in braking (other than mechanical issues):
Too much brake pressure. Locking the rear wheels or even just slowing them slightly will lighten the rear and make it unstable.
Too much steering combined with too aggressive braking. If you start to induce lateral load into the tires when they are already at their complete limit of available grip, they have nothing left to give and the rear will snap out.
Both happen when the tire is taken over its limit.
Was your previous kart an OTK model too? If not, they do have a pretty unique brake pedal feel compared to other karts that could cause some issues if you aren’t attuned to them yet.
What is your rear width? I always had issues on an OTK under braking if I tried to run the rear any narrower than ~1390mm. Seemed that with my build and seat placement, it raised the center of gravity too much and reduced stability on entry.
Is the kart tossing the rear to one side consistently? If so, something isn’t straight, time to put it on a table to confirm. Had that before with my son.
i will get a video of it next time i am at the track, i widened the front width more which stopped the front instability. that helped keep the rears controlled a bit more but still locking up very easily.
never had these problems when i raced juniors which makes me think its a mechanical issue.
it seems to be much more unstable when turning right, it could be a bend in something as i did have a big impact on the right side due to another driver
When you brake, you are shifting more load onto the front tires. Shifting the load forward will make the front end more responsive and take grip away from the rear. So if something is tweaked up front, it will show itself under braking.
If it is consistently pulling 1 direction, I would check everything. Ben kingpin, bent steering shaft, bent spindle arm, even a bent hiem end can be parts outside the frame causing it. Have also seen where a slightly shifted axle caused it. Then of course you have the bent bent frame possibility. A tweaked C, twisted frame, or bent rear fork can all cause it.
Desensitize OTK brakes? I think they’re the most desensitized brake I’ve felt, that and the eks one that’s also a direct pull. Not my preference for brake, gives me very little feel.