OTK brake problems, not working in high speed

Hello I’m new to an OTK just got my first this year and this weekend I was having some trouble with the brake system and wanted some input. I drove the kart for a race a few weeks before this weekend no issues, I come into this weekend the brakes on the stand were firm, they seemed fine, I go out first session the brakes were working at first, mainly in low speed corners but whenever I’d go into a corner at high speed the pedal would just go soft and fall to the floor and nothing would happen (had to spin myself out on purpose to not hit the barrier). After asking around the theory was that there was air in the lines, because in high speed corners there would be some much heat being built up making the brakes soft. We ended up putting new fluid in had a friend help us bleed the brakes to get all the air out and I still had the same problem on track. Someone helped us notice my brake pads were wearing unevenly probably because the axle could have possibly been shifting around not being tight enough. He also pointed out I was also using aftermarket brake pads which could have been causing the problem. Next practice day I’m gonna go make sure the axle is tight, throw some actual otk brake pads in and see what happens.

I wanted to know if anyone had any ideas as to what could be happening to cause this issues? And am i going in the right direction with what I should be doing? Anything would be appreciated

Update: in case anyone encounters the same problem, it was the axle that was moving around causing the braking problems, set screws werejt enough to keep it tight so i put lock collars on the axle to prevent it from moving and the problems went away.

Also sidenote make sure there is no air in your brake system and make sure all the connections are tight but not overtightened.

Your plan sounds good. After the axle is secured in place and the pads have been replaced, clean off the rotor with brake cleaner and center it between the pads.
Tip: Outboard of each rear axle bearing, wrap the axle with a couple of turns of electrical tape. If the tape is disturbed after a session, you’ll know if the axle has shifted.

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Is the axle moving left to right at high speed and knocking the pads back? Does applying the brakes twice cause them to work?

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Definitely sounds like the axle is shifting left/right and pushing the pads back. Make sure you’ve got all those grub screws tight.


I’m running a 2021 OTK in Tag for the first time this season and experienced the same thing. Going into the turn following a hard left the pedal would take a couple of pumps to have any feel. After all of the above diagnostic stuff I realized the axle was being allowed to slide in the bearings, compressing one caliper piston, and leaving a big gap on the other side. I’m guessing that pumping the brake was forcing the axle back to where it belongs. New bearings with fresh grub screws and a fat axle collar outside of each bearing seems to work. I’m told the axle collars will change the stiffness of the axle so at some point I will try running without them on a test day. None of this happens to my fellow racers so I’m a little baffled. There must be an expert out there with suggestions. Thanks all

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Not sure what is wrong but you shouldn’t need axle collars to hold the axle in place. At least I’ve never used axle collars to keep the axle from shifting. Are the grub screws the right type? The grub screws are cup point set screws. They do need to be tightened more than once, as they dig into the axle and lose thread pre-load.


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Agree with Larry. One of my items to check every session is the grub screws for the axle. They loosen if you don’t keep an eye on them.

Try to use the same grub screw indent in the axle, when swapping axles.

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I tend to put a little blue loctite on my grub screws. I also wrap the carrier with duct tape over the top of the screws.

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Thanks all, I’ve cranked the grub screws tight ( yes the proper type for this application) but never re tightned them as I thought it might defeat the lock tite. Somebody even suggested drilling a deeper dent into the axle, so I did that too. Next race is 9/10 so will see…