konman795

Hey everyone, I have a fixed gear bike and I'm having the hardest time locating whatever is loose on my bike that's causing this rattling sound. It only happens when I'm going over bumpy road or bumps. I can't replicate it unless I'm on the bike so I'm hoping someone has some ideas. The sound is definitely coming from somewhere near the front of the bike. I've pretty much taken everything I can think of apart and put it back together but still rattling when going over bumpy surfaces. It's absolutely silent when I'm riding on smooth surfaces though.

Took the wheel off, bounced it against ground. No rattling sound.
Checked brake caliper, no movement or loose parts.
Took compression plug out, re-seated spacers and stem, tightened both inner and outer screw area on compression plug to recommended spec.
Tightened stem to recommended spec.
Took drop bar off and put it back on, re-tightened to spec.
Took brake lever off and put it back on, re-tightened to spec.

I was thinking, could it be the threadless Michelin tube that I have? It doesn't seem like there's enough room for it make this rattling sound though. The noise wasn't there when I had a 700x25c tire on. It only started when I put a 700x23c tire on. I'm stumped, hoping someone can give me some suggestions. Thanks!

rhenning

A bolt or nut that someone put in your frame tube to drive you nuts. I have also seen a loose nipple bouncing around in deep section rims. The guys that build bikes sometimes get bored and do this. Roger

AAZ

I have a drop bar that makes some noise when it flexes.

e_guevara

Brake cable hitting the frame?

konman795

I know it isn't the brake cable. Would the drop bars be rattling when I roll over bumpy surfaces though? It's the FSA Omega Compact. I'll be getting 3T Ergosum's in tomorrow though so I'll be switching it out anyway.

noglider 

See Sheldon Brown-Bicycle Technical Information, as he has at least one good article on this.

SPiN 360

I had something like this and it turned out to be a strap on my helmet rattling against itself...
Also had an adjustable water bottle cage rattling because its adjustment screw wasn't tight.

FBinNY 

Mechanics, like detectives and doctors, hate coincidences.

Since it's new and started when you changed the tire, the culprit is probably related to that. If you have deep rims, there's a good chance that the valve has some wiggle room in the hole and may be bouncing against the lip of the rim's outer (toward the hub) surface. Possibly you didn't have the issue before because the valve wasn't perfectly straight and was forced against the side of the hole.

Don't take anything apart. Get a toothpick and jam it into the valve hole and break it off. If it solves the problem, either leave it there, or remount the tire with the valve not perfectly straight. If it doesn't you've eliminated one suspect and can move on.

SPiN 360

Another thought - do you have a valve stem with one of those little washers at the bottom that steadies it onto the rim? Maybe the washer is rattling.

e_guevara

If bolted down correctly the drop bars won't be rattling, whatever their brand may be. I'd be more worried of a faceplant if the bars were rattling.

FBinNY 

BTW- it could also be a loose headset. Setting the top nut by torque is a meaningless approach. If (for example) the steerer is a bit tall, than the top cap will bottom against the steerer rather than compress the headset, so you can torque all you want and still not tighten the headset.

TEST the headest the old fashioned way, by applying the front brake and rocking the bike forward and back while looking and feeling for any fork movement at lower bearing.

I don't like this theory because it's a coincidence, but it's still a real possibility.

konman795

All good suggestions, there's no play in the fork when I apply the brake and rock it so that's good. The tubes I'm using are threadless so there isn't a washer that tightens down. My old tubes did have those so I know what you're referring to. I'm starting to think it could be the threadless tube wiggling when I go over bumps. Do you think wrapping the contact point with electrical tape will dampen the sound?

FBinNY 

It might be the valve ---- and it might not be.

Don't do anything until you try the toothpick test (doesn't require any tire removal). If the toothpick solves the problem, than tape around the valve, or simply mounting at a slight angle, or whatever will work, because we know you can't ride around with a broken off toothpick wedged in there ---- perish the thought.

RULE No. 31 of repair. Never start the fix until you've confirmed the problem.

Hopslam

Heat shrink tubing would work well for this


Cheers & good luck

konman795

The issue was indeed the threadless valve rattling against the rim! I put some electrical tape around it and the noise is completely gone now! Thanks everyone!

JameB

Does your bike have a stand? They easily become loose on my bike :/