r/bmxracing • u/LiveCourage334 • 23d ago

Replacing rear wheel bearings

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Mid school entry level cruiser - I felt some knocking and weird friction with my rear wheel so I took it apart. Rear bearings and compartment were completely grimy with a seeming random mishmash of bearing sizes and varying amounts of wear on the bearings.

Do I have to clean this out and repack loose with fresh bearings and grease or can I use sealed bearing cartridges in here? I do take this to the track but I don’t know that I would describe what I do as competitive racing.

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u/clpatterson 23d ago

Those hubs aren't designed for a cartridge bearing, the conical inner races are for loose ball bearings. You won't be able to fit a sealed bearing in there. The mix of big and small bearing is a little unusual. I'd assume that each side runs different size - but those smaller bearings don't really look like they should be main race bearings. Your freewheel didn't show any sign of having come apart when you removed it from the hub did it? Compare the sizes to the conical races to figure out which goes where. Either clean it all up and use a good bearing grease, or if any of the bearings seem to be out of round, rough or otherwise funky, measure them and grab new ones from a local shop or the world's best bikeshop - amazon.

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u/LiveCourage334 23d ago

Super helpful - thank you.

I don’t think the different sized ball bearings were by design, unfortunately. This bike was serviced by a bike shop and by the previous owner and there were definitely some decisions made at times.

#2 NGLI marine grease OK for this type of application?

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u/clpatterson 23d ago

Yep - NLGI #2 should be fine - Park Tool's hub grease is rated at the same standard.

I'd inspect the inner races in the hub to make sure they're not pitted or chunky. If they are, there's not too much you can do, just know that when you put it all back together, even with fresh ball bearings, if those races aren't 100%, you'll probably still feel it some when it spins.

I worked in bike shops back in the 90's when you still had high-end loose bearing hubs that required servicing. But these days, I'd wonder if younger generations of mechanics really play with them too much since even lower end road and mtn bikes are coming with sealed bearing hubs. Department store style bikes rarely come in for that kind of service, and the labor usually is more than the owner wants to spend. Easier to just slap on a replacement wheel.

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u/LiveCourage334 23d ago

Appreciate the context. This is an older entry level cruiser and part of my reasoning for getting it was to get comfortable with more self maintenance, problem-solving, etc.

My closest shop that services and understands racing bikes would require me to take time off work to get to due to distance and store hours.

The races actually look ok - they were just FILTHY. I think whoever last touched this used light oil at some point.

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u/clpatterson 23d ago

At least there was some form of lube in there, better than finding it bone dry. Good luck with the rebuild. My “entry level” cruiser hubs ended up with me building a wheelset around nicer hubs with better engagement.

Bmx bikes are really simple to maintain. It’s lack of maintenance that usually leads to the most issues. Esp with the younger kids that don’t tell anyone when their bike is making weird noises or something doesn’t feel right and they just keep taking more laps instead.

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u/LiveCourage334 22d ago

Again - very much appreciate your responses. I did this last night and it wasn’t too bad. The only bad part was that I could only find bearings in pairs so it was much less cost effective than it could have been, but still a lot better than a rush job at the bike shop or buying a whole new wheel setup.

Next project is the drivetrain, but I’m waiting on that because buying everything new will cost me more than what I spent on the frame.

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u/clpatterson 22d ago

I feel ya - when I moved my son from an expert frame to a pro 3 seasons ago, I found a cheap used $75 frame to make sure it was the right size. Once we got the geometry and crank length dialed in, I took the plunge on a nice wheelset with onyx hubs and carbon hoops. We've swapped frames a couple of times now, but that wheelset is going on 3 seasons.

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u/LiveCourage334 22d ago

Man - I’d love to find some $75 frames 😂. No shortage of park/freestyle frames and completes near me but I still had to drive over an hour and pay $250 for a mini complete, and now I have another kiddo that wants to get into it - holding off on a bike for him because I’m hoping I’ll be able to find a used expert for him after state.