Bicycle Mechanics - wobbling freehub body
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02-26-10, 09:33 AM
here the thing- I was cycling home last week and noticed that the rear wheel wasnīt feeling particularly smooth. When I was coasting for example the chain would be twitching. I took the rear wheel off and noticed that the cassette was very wobbly. The ring holding the cassette on was perfectly tight so I took the cassette off and the problem was with the freehub body (which holds the cassette on the wheel). The freehub body was quite wobbly so I think this is where the problem lies. The wheel axle (edit I mean skewer) was perfectly straight and could be withdrawn from the wheel without problem. So it looks as if the problem lies with the wheel bearings but it did not seem that the locknuts were particularly loose. As I have not played around with this wheel since I bought it a few years ago I am thinking that the problem is due to wear.
So before I take the wheel bearings apart can any of the more experienced mechanics tell me what the best course of action is. Of all jobs on bikes playing with wheel bearings I find to be the most frustrating and time consuming. So any suggestions here as to things to check would be very much appreciated (taking it to the bike shop though is not an option for me so please donīt suggest that).
I'm trying to visualise what's moving. Is the freehub body moving even though the axle is not, or is does the whole wheel wobble when the axle is held tight. If it's the first, then then the problem is in the freehub itself. You can service the bearings, but if there's another problem, you're probably sol. From Park tools (http://www.parktool.com/repair/readhowto.asp?id=45):
Be aware that it is not recommend to completely dismantling the freehub itself. There are no parts available, such as the pawls or springs. The small ball bearings are available as replacement parts. However, if the bearings are worn out and require replacing, it is very likely the entire freehub is needing replacement. The blow-up image seen below is a ball bearing type freehub.
http://www.parktool.com/images_inc/repair_help/freehubparts.jpgIf the whole wheel has play, then obviously just take it apart and service the bearings. I'm hardly the most experienced mechanic, but the amount of time this takes drops very quickly with a bit of practice, as does the frustration level.
I have a wobbling hub body. I took it apart, cleaned it up, lubed it up, put carefully back on and it still wobbles. It must be just worn out. So, I'll have the wheels rebuilt with new hubs. Removing the bearing cone/race is hard without special tool. You'd be probably better off replacing it, the bodies are like $30.
02-26-10, 01:04 PM
thanks for the help guys- I can wobble the freehub body when the wheel is not mounted on the bike (without the axle; edit I mean skewer)- so I am thinking that it is probably just worn out. It has seen some action so it is to be expected. I had the feeling is was not just a classical bearing problem (as the bearings did not feel that loose i.e. - no real lateral play as you would expect with losse bearings). So like Adamdz I have the feeling that if I try to just do a bearing service it would probably not hold for long. So a new axle is probably the best solution here. Luckily I have a spare wheel to be riding on for now.
It might or might not be perfectly normal for freehubs to wobble based on their particular design. Also for this purpose, I'm defining wobble as side to side, or up and down movement most visible when the hub spins while the freehub is stationary.
basically we can divide freehub designs into two classes.
1- those mounted directly on the axle with their own bearings and connected to the wheel hub only through the clutch (ratchet) mechanism such as the Campagnolo system These run true because they are independent of the hub itself, and do not turn when not pedaling.
2- self contained freehubs with internal clutch and fixed to the hub shell via spline or thread, such as most Shimano freehubs. With these, ome wobble is normal because the axis of the freehub rotates with the wheel so even though the cassette is stationary it's axis isn't, and any mis-alignment at the mounting point will cause wobble in a way similar way that a bent crank will cause the pedal to oscillate underfoot. Wobble within the normal range is no problem, though many are surprised when they first notice it. Older riders used to freewheels are used to seeing and accepting it.
If the wobble is slight, I wouldn't sweat it, if it's significant on a design of the second type it might mean that the freehub/hub interface is loose, or damaged to the point of imminent failure. It's a judgment call, based on knowing what normal runout looks like. You might also want to double check that the connection to the shell is tight.
02-26-10, 03:27 PM
It might or might not be perfectly normal for freehubs to wobble based on their particular design...
in this case the wobble was quite bad- in fact when I was cycling home I really thought the wheel was in danger of coming off. I got off at one point and checked that I hadnīt lost a spoke and was baffled to see everything looked normal. It was just when riding particularly when the cranks not moving that I noticed the chain twitching and jumping around and the only reason for that can be cassette twitching. Then when I took the wheel off I could feel that the cassette was moving way more than any normal play.
Sounds like a failure, either at the bearing or the hub/freehub connection. What brand hub, and is the wheel secure (no play) on the axle?
02-27-10, 01:41 AM
Rear Hub: Shimano FH-M585
you can see the bike in this thread (when it was a lot newer)
If you have excess play in a Shimano style cassette body, it's pretty easy to fix, if it's the type that has a couple of slots in the axle bearing cup that screws onto the core of the cassette body. Just get a bit of plate steel, cut it to size and drill a hole in it. The cup has a right-hand thread, IIRC... obviously you need to sit the cassette on the hub spline.
If you're game, you can clean and regrease the bearings, but you can just pick out one or two of those shims to remove the play.
Easy if you happen to have a piece of steel the right size and adequate cutting tools :D Isn't the play caused by wear so this would be just postponing the replacement, anyway?
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