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This morning on the way to work I noticed that my DH's duraAce gruppo was making the same kind of noise while coasting that my Campy stuff makes, only a little louder. He didn't seem concerned, but I was because it normally does NOT make a coasting noise. Any idea what that is?
He has a 200k this weekend and I'd hate for him to do it on bearings that are going out or something, there's several thousand miles on this bike just this year!
thanks so much!
The coasting noise comes from the pawls inside the freehub. The freehub is the replacable part of the hub that the cassette attaches to. The freehub can theoretically be disassembled and overhauled (50 bearings inside and maybe 4 pawls) but Shimano quit selling the disassembly tool and now recommends that freehubs simply be replace when worn out (~$50 for the Ultegra version, I believe). The freehub can be soaked in solvent and then relubed with oil (see http://www.parktool.com/repair/readhowto.asp?id=45) if it is sticky. That might be worth a try in this case. The excess noise might indicate lack of lubrication inside. If you spin the rear wheel without touching the pedals, do the cranks spin? That would indicate a sticky freehub. Does the bike ever seem to freewheel forward, ie. the pedals turning don't move the bike immediately? That would indicate failing pawls.
I've never run into this specifically, so can't say why a freehub would suddenly sound louder. Worst case would be a broken pawl that's chewing up the inside of the freehub. If the freehub fails, it would either freewheel both forward and back so it's constantly coasting, or it would seize so the bike becomes a fixie. If it sounds pretty much like your Campy freehub when coasting, it may be fine with some fresh lube.
thanks so much, I'll see that he checks tonight!
ah; the DH responds:
Two points:
1. I don't have a 200k this weekend. I have a 225k.
2. I don't have a Shimano freehub. I have a Phil Wood rear hub that is fully rebuildable. It was recently rebuilt and is in fine condition. I am not concerned about it, but will listen closer tonight on the way home and check it out in the garage.
Thanks again! sounds like we can avert a problem before it gets too serious.
Deb definitely gave you some great advice! The other thing that I would do is repack the entire hub... there are bearings inside the freehub as well, and everything might simply be dry. A quick way that you can test that is take the wheel off the bike and hold the wheel in your hands so that you are holding onto the axle(not the quick release) when you spin the wheel it should feel very smooth. If it doesn't, or it seems to catch, have the entire hub repacked and check the pawls as well. Good Luck!
Ah yes, the noise has nothing to do with the group (unless the group and the hub happen to be the same). It has more to do with the brand of wheel and what kind of freehub they use. Some are noisy like Campy, Chris King, etc. Some are quiet like Shimano. Shimano is quiet because it doesn't have the same types of prawls that other wheels have. Other wheels need to click through each prawl, and the more prawls the noisier the wheel. Correct me if I'm wrong, but Shimano hubs don't need to "catch" like others on one of these when you start pedaling. So, when you stop pedaling there isn't so much of a clickclickclick noise as the hub spins without being engaged by pedaling.
If he's recently had the hub rebuilt, then unless someone just screwed up servicing it, then I wouldn't worry about it. Maybe that's the sound the wheel is supposed to make when in good condition. Also, if the hub was changed at all, maybe the new parts have a different sound than the original. He might want to take a peek and see if anything is loose, but since it's not a Shimano hub, I wouldn't worry too much about the noise.
Last friday he rode the bike 140 miles during which it rained the whole time . That could clean the grease out of anything!
Well, Raleighdon is at the bike shop right now. They found the rear hub to be dirty and dry inside. Aha!
thanks Deb!!