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bent axle?(11 posts)

bent axle?E-ticket
Nov 9, 2001 12:11 PM
Is it normal for the cassette to precess about the axle while the rear wheel is freewheeling? Mine precesses ~ 1-2mm. LBS says it's normal, I get the feeling they're trying to avoid fixing it under warranty.

1) is this a problem?
2) should they cover it under warranty?
3) if they won't, how easy is it to fix? (I'm OK with the wrench).

Thanks, Eric
Explain what you mean by "precess"Rusty McNasty
Nov 9, 2001 12:30 PM
Please stick to common English.
Explain what you mean by "precess"cyclaholic
Nov 9, 2001 12:42 PM
I think what he is saying is this:

When he is freewheeling, he looks down at his cassette and sees it wobble a little bit as the rear wheel spins.

I think I understand because I've seen this phenomenon on some of my old clunkers.
OK, thenRusty McNasty
Nov 9, 2001 1:31 PM
It's not a bent axle, because the axle stays stationary. Cog runout (which is what I think you mean) can mbe caused by a number of things, but not by a bent axle. Usually means you have either bent cogs or a cheap wheel.
Webstergrzy
Nov 9, 2001 1:54 PM
Precess: To move in or be subjected to precession.

Precession: A complex motion executed by a rotating body subjected to a torque tending to change its axis of rotation, characterized, for constant speed of rotation and constant magnitude of the applied torque, by a conical locus of the axis.

Precession is a pretty common term to anyone who has taken a basic physics class, has seen a gyroscope or knows anything about the movement of the planets. It is exactly the right term to describe what he's talking about. If you're illiterate or too lazy to use a dictionary (online even) then keep your inane comments to yourself. No reason to dumb-down the forum for your benifit nor for you to demonstrate your ignorance for ours. One would have to question your ability to answer the question.

In any event the motion comes from either a hub body that is not sqaure with respect to the axle. this can be caused by the hub body/hub interface or the hub body itself not being perfectly square. Things (hub/hub body) can also be bent, but it wouldn't be caused by the axle.
He means "precess"Kerry Irons
Nov 10, 2001 6:28 AM
No dictionary nearby? Sheesh! McNasty is right.
How to proceed?E-ticket
Nov 9, 2001 2:57 PM
Ok, should I do anything about it?
Should I just ride and forget about it?
Will it get worse?
Should I expect the LBS to service it under warranty? (< 1 year old Vector Comp, ~1500 miles)
Is it servicable by the weekend mechanic, without high liklihood of destroying the wheel? (I can maintain cone/bearing hubs just fine, but haven't been inside this Hugi hub yet)
If so, how?

Thanks again, Eric
Not to worry (much)Kerry Irons
Nov 10, 2001 6:37 AM
You didn't say what brand/model you have. In general, this "problem" is worse in lower end components. Sometimes there is an element of optical illusion to it, as the shifting ramps make it LOOK like it's wobbling, when in fact it is not. Since you say there is a 1-2mm wobble, I presume you've measured it. Most likely there is some slop in your cassette mechanism, but unless it gets worse, there is not much to worry about. In freewheel days, this was a very common thing.
Axle not likely at faultCalvin Jones-Park Tool
Nov 9, 2001 3:05 PM
What you are seeing is common. Go to any store, and spin the wheels and you will see this. The axle is not the issue. It is not rotating in the dropouts. The tolerances in the bearing surfaces of the freehub are not zero, and so you get this slight movement. Put the bike in a stand to get a good look at it. Pedal the bike and now watch the movement. When you coast, there is movement between the inner and outer parts of the hub, but when you pedal the pawls lock in and the two move together.

There is nothing you can do for a "repair". If it causes a problem in shifting and riding, it certainly is a "problem" needing a solution. The shop is correct in stating it is typical of bikes.
Thanks (nm)E-ticket
Nov 9, 2001 3:26 PM
re: bent axle?CT1
Nov 10, 2001 5:40 PM
Yes, this can be a problem!

Pull the cassette off and clean the hub body, spacers, and cogs carefully. If you still have the precession after this then your hub or cassette just sucks HT.

Good luck
JohnG