Bicycle Mechanics - BMX Quando rear hub overhaul?
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07-12-11, 09:08 AM
I ran into a problem disassembling a hub from a low-end Haro bike. I normally work on road bikes and don't have experience with BMX designs, but hey how different could it be? Turns out quite a bit.
I removed the single sprocket (cassette? driver? not sure what to call it) from the hub drive side okay. The sprocket has cups on both sides to hold ball bearings. It fits onto the axle via a fixed axle cone on the inner side and adjustable cone on the outer side. There are 4 pawls held by a single spring in the hub, and these ratchet over teeth on the sprocket. Pretty neat idea.
On the drive side, the axle is held in the hub via what appears to be a press-fitted sealed bearing. On the non-drive side, the axle is secured to the hub via a hub cup and ball bearings/adjustable cone that came apart fine as well.
The axle rotation on the press-fit bearing feels really rough and the axle has a lot of play. I think the bearing is damaged or dirty, but I can't pull the axle out though to access it. Do I need a special tool to service/replace it?
Thanks to anyone who can help.
Don't fancy your chances of useful replies without pix.
07-12-11, 05:35 PM
strike the axle to pop out the bearing. the axle is shouldered.
07-12-11, 06:35 PM
Thanks for the info reptilezs. Do you mean strike it from the non-drive end? If the axle's shouldered on the inside of the hub, and outside there's a fixed cone built into it, then how the heck does the bearing come off the axle? Is the shoulder a removable sleeve (maybe threaded onto the axle)? Do I need some type of puller to get the bearing off the axle or will it just slide off? Also, once I've replaced the bearing, do I simply strike the axle on the drive side to re-insert (press) it back into the hub body? More tips please :)
07-12-11, 06:59 PM
the non drive side has loose balls. traditional cone and lock nut. these hubs are weird. the drive side cone and locknut it to adjust the freewheel bearings
07-13-11, 10:28 AM
210686Yeah it's definitely strange. It's a hybrid design with axle supported by a cartridge bearing on the drive side and cup/cone/balls on the non-drive side. Anyway, I popped out the axle by striking it on the non-drive end and sure enough, on the segment of the axle running inside the hub body, there's a sleeve and a nut to hold the cartridge bearing up against the flat side of fixed cone built into the drive end of the axle. Now off to find a new bearing! I'll post a pic of the axle later for those interested.
07-30-11, 09:22 PM
Crap. Replaced the cartridge bearing and the loose bearing sets but the original problem - driver skips/slips - is still there. I thought it was skipping because the hub and driver bearings were damaged leading to alot of play, but it looks in the end like the real problem is that the spring clip that pushes the pawls up to engage the driver teeth is just too weak. When I push down on the pawls they don't 'pop' up strongly (I lubed them and the spring with oil).
Where the heck can I get a new spring? I checked with a bike shop that sells these Haro BMX's but they say they can't order parts for this hub except for a warranty issue. Emailed Haro and did not get any answer. And I can't find the website of the hub manufacturer either. Now I understand why there's this big aftermarket business for BMX components. Sell bikes with crappy components and no available spares supplies. What a racket... this sucks.
07-31-11, 03:38 PM
this is so true for most freehubs ,no matter who makes them or how many speeds ,once the freehub fail the only thing to do is replace it ,it what they mean by no serviceable parts inside . no replaceable parts available .
08-01-11, 07:50 PM
Actually, the real bummer is you can get pawls and springs for the popular BMX brands... so I guess it's a pretty common failure. See http://www.danscomp.com/shop-PARTS/HUBSACC.html.
I mean, couldn't Haro carry some minimal stock of such parts? They must have sold thousands of bikes with this hub in the last year. The only alternative now is to buy a new wheel or at least a hub (pretty pricey if you look at the gear on danscomp).
Oddball gear. That's what, 9t?
IMO it should be feasible to fashion a stronger spring out of suitable wire.
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