OTK broken spindle


OTK spindle axle broken. Has anyone else experienced the same? It happened unexpectedly. There was no competition situation. No collision. I was practicing as usual on my home track. Suddenly, after a corner, the car went straight off the track. I wondered what happened? Spindle axle was totally broken. No bending or any warning signs. My kart is a 2022 Kosmic Mercury RR. I find this worrying if you can’t trust the OTK steering.

Thanks !

Odd place to break… Has the arm been bent and straightened previously?


Yea, previous damage would be most likely explanation. The top and bottom shows signs of fatigue consistant with an upward stress that was returned downward. Its positioning off the weld is also consistent when damage I have seen bends when inflicted on a spindle flag.

Glad your alright, that could end badly definitely understand your concern.

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Glad you’re OK. In my experience it’s not a common failure for any brand.


It looks like it bent upwards, and normal steering input won’t do that. Could it have caught a curb or something like that and got a hard upward kick?


I was also wondering that there was no marks of any previous bending. Arm has never been straightened. For my understanding the arm should deform and not break in case of enough stress and not function like a brittle spring. Naturally I was thinking of the OTK quality control (welding embrittlement, material etc.). I was glad that that our local OTK dealer gave a new spindle free of charge.

Yes I agree. It has not been straightened before

I’m not thinking that’s a defect or QC issue. It was loaded funny. Either something came up from below like a curb or it was set down in a way that the kart’s weight was supported at the end of the spindle. Have you ever picked up the front end by the trailing edge of the spindle?

It’s a really bizarre break. Admittedly I am not a material scientist and not sure what the fracture face does or does not say, but just from empirical experience I haven’t seen failures like this.

Typically when a spindle arm breaks it bends in a torsional fashion beyond the elastic region. Usually this seems to happen by a hyper extension of the steering hard right or left in a crash where the spindle arm hits the frame and is bent upward or downward.

@dodo seems to have more experience. Potentially the heat introduced in the initial weld just made the arm so brittle it just failed?

I add that as I’ve seen this type of “mysterious” failure at the stub axle to the ‘step up’ shoulder junction look like this.

Either way, glad you’re ok, and that the local OTK dealer sorted you out. Most OTK parts are regarded in the industry as well engineered and durable. Some are of the opinion the last few years they’ve ‘cheapened out’ on materials with a race to the bottom approach on raw materials but I don’t really know on that either way.

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My hangup with that is that you can see the arm bent a lot before breaking, and it bent in a weird direction that is not in the direction of normal load. Something lifted the trailing edge of the spindle what looks like an inch before it snapped. If it was a HAZ issue (heat affected zone), I’d expect the failure to be closer to the weld interface. You can see that the arm still is attached to the weld, so the material closest to the weld was fine.


Did you try rubber-banding it back together? Glue, maybe?

Credit to @KartingIsLife for the meme below, but I found it applicable:

No, I fixed it with Blue-Tack.

This is a fatigue failure for sure. Blue is the final fracture surface and my best guess in red is the initiation.

I would think it either had a material issue in the metal or some event a while ago started it. It would get loaded vertically every time you corner with the caster that’s in the kart, albeit not directly vertical.


@Matt_Geist you beat me to it…was typing at same time. My guess is heat affected zone from the coloration and proximity to the weld, but that’s a guess. Definitely a fatigue failure. There was a crack there before it broke off!


I feel like I’m watching one of those air crash investigation episodes right now :laughing:


I actually checked my spindle and tie-rod angle when this was first posted. Technically, there is a vertical component, but it is not from caster. It is is from the angle of the tie-rod to the spindle. Because of the steering column angle, there’s almost no upward angle at all. In other words, the tir-rod is dang near parallel to the spindle arm. I’m sure we have all seen tie-rods break when hitting a barrier, so there’s just no physical way a tie rod can exert the upward force necessary to have done this. I’m convinced the arm was already bent upward, and this weakened it significantly to the point that normal operation then fatigued the already-compromised section.