Loud intermittent metallic clacking from rear hub

[Maximzodal]

I have an Electra Townie 21 with less than 600 miles on it. I clean and lub the chain often. The hub is a Shimano MegaRange Super low 14-34T. About 50 miles ago, an intermittent metallic clacking started coming from the rear hub. Like metal hammering on metal. It would continue during freewheeling or back peddling and the rate increased with speed. It has become progressively louder but still intermittent. A tack-tackity tack-tack repeated. But, it may almost go away on a 5 mile ride or return with a vengeance or it may be there the whole ride, staying loud or getting louder or quieter. I recorded the sound holding a small digital recorder toward the hub. It sounds like a metal striking metal.

The local shop service guy put it on a stand but there was no noise. After a ride, he told me his bike did the same thing and dismissed my concerns. I wondered if it could be a bearing going bad, with the race getting stuck and releasing intermittently. But he told me the bike isn't old enough? My confidence in his assessment is sorely lacking. It is definitely not normal.

When I click on "Add an Attachment" to upload a short m3 of the noise, this window is kicked back to the top but offers no way to add an attachment. It says I'm 'currently using N/A of your allocated attachment usage (Unlimited)'. I have no previous attachments. Does N/A mean not allowed?

A short mp3 of the sound might allow someone to diagnose the problem.

Thanks,
Max

[1FJEF]

Well one of my old bikes does that, but it has a freewheel, not a cassette & freehub. I don't think the wheel bearings could make that kind of noise, there would be more grinding & popping. Maybe the freehub.
Your LBS should have tried harder.
Are you mechanically inclined? You only need a few tools to be able to take things apart back there. Oh, & some grease too.

[DaveM]

If it only happens when you're coasting, I'm thinking it's a bad bearing/pawl in the freewheel/freehub. If you have a 7 speed "mega-range" gear cluster, I'm pretty sure that's a freewheel, not a cassette. So, I'm voting that you have a bad freewheel. If so, could be fine (but annoying) for years. Or it could suddenly fail and you won't be able to pedal forward at any time.

It could also be a problem in the rear hub bearings. You would expect this to show up when you're pedaling as well as freewheeling, but sometimes these things are tricky. This is a more immediate issue since if it is a bad bearing, it could be destroying your hub meaning you will need to get a whole new rear wheel.

It's tough for any mechanic to diagnose something when the bike refuses to do what it's doing when you bring it in. You may want to pay them to rebuild the rear hub to rule out it being bad hub bearings. There shouldn't be any doubt once they can inspect it visually inside.

Last thing you could try. Lay the bike on it's side, spin the rear wheel, find the border on the rear gear cluster between where the center part rotates and the outer part stays still. Drip some thick oil like car oil in that crack and let it work in for a few minutes. If that changes the sound you hear next time it does it while riding, it probably means the problem is the freewheel.

[Maximzodal]

(06-04-2012, 08:34 PM)DaveM Wrote:  If it only happens when you're coasting, I'm thinking it's a bad bearing/pawl in the freewheel/freehub. If you have a 7 speed "mega-range" gear cluster, I'm pretty sure that's a freewheel, not a cassette. So, I'm voting that you have a bad freewheel. If so, could be fine (but annoying) for years. Or it could suddenly fail and you won't be able to pedal forward at any time.

It could also be a problem in the rear hub bearings. You would expect this to show up when you're pedaling as well as freewheeling, but sometimes these things are tricky. This is a more immediate issue since if it is a bad bearing, it could be destroying your hub meaning you will need to get a whole new rear wheel.

It's tough for any mechanic to diagnose something when the bike refuses to do what it's doing when you bring it in. You may want to pay them to rebuild the rear hub to rule out it being bad hub bearings. There shouldn't be any doubt once they can inspect it visually inside.

Last thing you could try. Lay the bike on it's side, spin the rear wheel, find the border on the rear gear cluster between where the center part rotates and the outer part stays still. Drip some thick oil like car oil in that crack and let it work in for a few minutes. If that changes the sound you hear next time it does it while riding, it probably means the problem is the freewheel.

Thanks for the response.

Sorry, I wasn't clear. The noise is there, peddling or coasting. The bike shop repair guy rode the bike and heard the same thing, then dismissed my concerns. It may be my imagination, but it seems the noise is 'felt' through the frame.

I'll try the oil suggestion. And I might take it back where I bought it for a second opinion. The local shop is a couple of miles the Electra dealer 20.

[trevgbb]

sounds like a repair or replace under warrenty to me.

[1FJEF]

Did you buy it new from an authorized Electra dealer?
When did you buy it?