I don't like rattling noises.
February 3, 2012 5:16 PM   Subscribe

Can you identify this bike noise?

I brought my bike into the shop this afternoon for a tune-up, and when I got it back it was making this rattling noise (begins 2 seconds in) from somewhere in the vicinity of the rear wheel.

The shop claimed that it's the chain scraping alongside the cage of the front derailleur, and that I could eliminate the noise by adjusting the derailleur with the gear shifter at my left hand.

I was happy with that (I know nothing about bikes), but a) playing with the gear shifter doesn't seem to eliminate the noise and b) the noise happens even when I'm coasting and the chain's not moving. I'm worried something else is wrong.

Some other information:
* the noise sometimes starts as soon as I get on the bike, sometimes not.
* hitting a bump in the road often makes the noise

Any advice would be great. I'm happy to provide more information if that would be helpful.
posted by dd42 to Travel & Transportation (14 answers total)
Do you have fenders on your bike? It sounds like tire rub against fenders, or just them rattling on their own. If you get off your bike and bounce it against the ground (i.e. lift and drop the back wheel a few inches), can you reproduce the noise?
posted by supercres at 5:21 PM on February 3, 2012

Response by poster: No fenders. I can't replicate the noise by lifting and dropping the back wheel.
posted by dd42 at 6:07 PM on February 3, 2012

I wonder if the rear derailleur might barely be touching the spokes. It could be close enough that it would only touch with weight on the rear wheel but...if moving the derailleur doesn't make a difference I guess it wouldn't be that.

I wouldn't think it's the chain hitting the front derailleur if it happens while coasting.

Do you have a reflector that might be rattling? Are any of the spokes noticeably loose?
posted by ghharr at 6:12 PM on February 3, 2012

Boyfriend and former bike shop guys says:

is rear wheel in straight and quick release tight?

do you feel it in the pedals or is it just a noise?
does it change based on your speed? (if speed, then wheel associated)
did you get new cables? they could have moved the cables on the F or R derailleur - they could be hitting the wheel.

Going along with the cable idea, the noise should only happen with specific gear combinations: so try out a few and see if it changes.

Boyfriend is convinced that it is a cable hitting something.

Doesn't sound like cassette body.

He also points out that a good mechanic would fix this problem without charging you. Your mechanic should be the one diagnosing this - and s/he should have given it a test ride before handing it back to you. No refund here, but the bike should not be making weird noises after a tune up.

His (no guarantee) diagnosis is front derailleur cable hitting something.

Hope you're back to quiet riding soon.
posted by sciencegeek at 6:26 PM on February 3, 2012

(he also says, if you're in the NYC area, he'd be happy to take a look at it)
posted by sciencegeek at 6:48 PM on February 3, 2012

My first guess was a chain rubbing against the front or rear derailleur, but coasting eliminates that option. The other things that could cause it are rotating elements - the wheels and spokes - hitting something else or maybe bearings.

Go to the shop, have them coast on it, or follow you while you coast on it. This is likely a free adjustment to cable or component placement.
posted by zippy at 7:18 PM on February 3, 2012

Did they overhaul anything? Rear hub, maybe? What brand and model of rear hub/wheel is it?
posted by Pseudonumb at 12:09 AM on February 4, 2012

Reason I ask is because I'm concerned about the smallest cog on the rear cassette coming into contact with the chainstay of the frame. (Check the tightness of the cassette lockring, now that I think about it.) Or possibly something being off within the freehub/pawls mechanism.
posted by Pseudonumb at 12:38 AM on February 4, 2012

Can you reproduce it by spinning the back wheel while lifting it off the ground?

Things that might be grazing the spokes: brake cable, kickstand.
posted by jon1270 at 5:59 AM on February 4, 2012

The shop claimed that it's the chain scraping alongside the cage of the front derailleur...

That's exactly what it is. I've had the noise, myself. The issue is that the front derailleur isn't exactly aligned properly. As it moves across the gearset, it should come to rest just outside the chain enough so there is no rubbing. There are small set screws for adjusting this.
posted by Thorzdad at 6:02 AM on February 4, 2012

Turn the bike upside down, resting the seat and handlebars on the ground. Now pedal the bike with your hand on one pedal. If you can hear the sound, it's much easier to visually track down this way than as you are riding on the bike.
posted by cocoagirl at 6:32 AM on February 4, 2012

Best answer: Do you have a rear rack on your bike? What it sounds the most like to me is the struts that connect the top of the rack to your seatstays are vibrating. They might be a little loose or just at the right place where they can vibrate and then rattle against the rack itself.

If you don't have a rack, it could also be cable housing rattling against the frame somewhere, but it sounds a little too loud and too deep for that.
posted by helicomatic at 9:12 AM on February 4, 2012

Is it the plastic piece that goes between the gears and the spokes on the back wheel?
posted by Sonic_Molson at 9:44 AM on February 4, 2012

Response by poster: The stays on a new rack were being vibrated and making the noise - helicomatic had it. Thanks everybody!
posted by dd42 at 1:11 PM on February 4, 2012

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