Hubs shifting during race

Using a medium length hub on a 50mm axle and the hub keeps moving in when running 1390mm width after 5 laps or so. More than half the hub is on the axle. Anyone have this issue any suggestions to stop it from coming in?

I assume you mean 1390mm rear width.

Either way, first thing would be to make sure the inside of the hub and the axle are both cleaned properly, with something like brake clean or starting fluid to make sure all grease and stuff is gone.

Then you may want to invest in some axle spacers like this: https://www.ebay.com/p/7004261210?iid=253016795925&chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=253016795925&targetid=930621147300&device=c&mktype=pla&googleloc=9018882&poi=&campaignid=10454921411&mkgroupid=109413765331&rlsatarget=pla-930621147300&abcId=2145999&merchantid=118929918

They’ll keep the hubs from moving in, and they make rear track width changes a little easier.

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I use 50mm lock collars against the hub. I’m sure somebody is going to yell “That stiffens the axle!!” I don’t care.

never seen these before. Looks great, I’ll get these. Thank you

How many bolts are on the hub? If it is just 1 pinch bolt I have found you need to tighten them as much as possible, grease the threads too. An impact gun works but I find the allen heads take a beating, keep spare bolts on hand if it starts to get a sloppy fit. You can also use a little leverage on your allen wrench.

I agree. I use these on 40mm axle. Also makes adjustment easy since there is always a reference. Going in move collar first. Going out move hub first

Sorry what is a lock collar?

Yes only 1 bolt. I have been cranking them pretty tight.

An extra locking ring you can butt up against the hubs, to stop them shifting.

https://cometkartsales.com/Axle-Lock-Collars/

Ok thank you all for your help

I’m not seeing how abutting a narrow lock collar right up against the inside of the hub will have any significant effect on axle stiffness.

Spencer, I agree with what you are saying but I’ve had the “stiffens the axle” argument used on me before.

I got the collars this morning. Racer next to me said they stiffin it too but he couldn’t explain it lol. I figure, even if they do stiffin it abit is still better of them the hubs moving in. Looks like the newer hubs have a set screw in them that go into the key to ensure they don’t move.

Stiffen. Stiffin something has a whole other meaning hahaha

The external lock collars stiffen the axle such a tiny insignificant amount it isn’t even worth worrying about. The internal rings don’t stiffen it at all.

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ok good to know, went with the collars because the track had them. Looks like the rings are not as possible.

Another option is to drill and tap the hub above the keyway and use a grub screw.

The internal spacers are the most logical way to stop hub movement assuming your hubs have an internal shoulder which pretty much most 50mm ones do that i have ever encountered. Added bonus is the track adjustment is simple.

The racer next to me had this with his hubs. Do you drill into the key too?

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No just use the grub screw to grip the key vs the axle so you’re not damaging it.

Generally you shouldn’t have to do it, but I had a kart that had this setup on it when I bought it once.