Bicycle Mechanics - Play in rear hub after each ride, even after pre-ride adjustment
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I'm experiencing an annoying problem with my rear hubs. They're pretty standard Shimano hubs with quick releases (one's a Deore, others are Deore XT). They seem to develop some play after short (~5 mile) rides, even if the cones and quick-release seem to be well-adjusted before each ride. I think the problem might lie in how I tighten the locknut in small increments while checking for play. I think that I might not be able to detect tiny amounts of play at the rim, so I might be under-tightening the skewer. But I don't understand why the hub develops more play as I ride. Is this bound to happen if I undertighten the skewer?
While I'm at it, I might as well ask how tolerant cup and cone hubs are to overtightening. I suppose this might depend on the thread pitch of the skewer, but does it make much of a difference to the hub's longevity if I tighten an eighth of a turn past "just right"?
06-02-10, 07:59 PM
overtightening bearing cones will lead to increased wear and bearing loads. sounds like you are not tightening the lock nuts/cones together with enough torque. dont forget the drive side has a locknut/cone too
what usually happens is that the cone or nut will slip and either over or under tighten from what you've intended.
I would say that the amount of force needed to keep the nut and cone from slipping is about the same as keeping a greased seatpost from slipping.
when the skewer is at its proper tightness, the axle will compress ever so slightly, taking up that slight looseness when there is no skewer on the hub.
and 1/8 turn is too much, it's more like 1/24~1/32 of a turn to compensate for some slippage of the cone while tightening against the lock nut.
either that or your axle threads are stripped...
06-02-10, 08:27 PM
Wheel gremlins? Hope you don't end up in the nuthouse :)
06-02-10, 09:15 PM
Any chance the rear axle is broken? The clue is that one end of the axle turns independently of the other when you try to adjust the cones and locknuts.
06-02-10, 09:33 PM
i would look closely at the axle... i had a similar case and the threads had just worn off or been partially stripped by accidental over-tightening.
06-02-10, 10:08 PM
Remember that you want to adjust the cone tension with the skewer locked in the axle with your normal skewer tension in place. The skewer compresses the axle enough to make a noticable and important difference. You'll need some really thick washers or bits of flat bar stock with 5 mm holes drilled through them as jigs to be able to set it up so you can do this without the skewers locking things in place. Actually if one has an axle sized hole in it so it seats against the lock nut and the other has a 5mm hole in it so it seats against the end of the axle and they are made from 1/4 steel stock that would work like aces. The one with the small hole will allow you to work the wrenches on the one side to adjust the tension. And if you have a bench vise you can clamp the other square or rectangular jig part in the jaws to hold the axle while you're adjusting the axle. But you'll need to take it out of the vise each time to evaluate the amount of axle preload.
As for the tension you'll find that as you tighten and test in very small increments first the play will go away. And with a couple of more degrees you'll feel some smooth and slight drag. Tighten a couple of more degrees and the bearings will feel like they are cogging or as if there's something inside that the balls are tripping over. The first case where there's just barely no play is too loose. The third where you can feel roughness or cogging is too tight. The "just right" is when there's a little bit of smooth drag. If you try to set it so the play just barely goes away in use and under pressure the balls will not retain enough preload. That's why you need to set them so there's just a little bit of drag more than what it felt like when there's just barely no play.
And when it comes to setting them changes of 2 or 3 degrees of rotation is what you're working with. 1/8 turns are extremely coarse.
Oops, I should have been more specific about the 1/8 turn thing. I meant to refer to 1/8 turn of the skewer's nut, rather than the cups and cones. When it comes to the cones, I've been following the advice given by AEO and BCRider (and Sheldon, etc.). So I put one end of the axle in an axle vise, adjust until there's no play, then back off by about 10 degrees.
My theory is that the hubs are adjusted OK (and the axles aren't stripped), but I'm just undertightening the skewer by a tiny amount because I'm mistaking what's really play at the axle interface for flexing at the rim. That might explain why this happens on several hubs, across several bikes. That's why I'd like to know whether it's okay to tighten the skewer nut just a little bit more than I think yields "no play". But I will go and check the axle threads and the cone+locknut tightness again to be sure. Thanks!
The "just right" is when there's a little bit of smooth drag. If you try to set it so the play just barely goes away in use and under pressure the balls will not retain enough preload. That's why you need to set them so there's just a little bit of drag more than what it felt like when there's just barely no play.Thanks for this tip, I'll try to adjust the axle while it's under compression from the skewer.
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