Annoying (concerning) Mystery Clunk

Benjo74

Back on the bike this morning (I bottled it yesterday - first day back at work after 2 weeks off) and all the way into work my bike was making an unusual clunking noise as I rode.

The noise sounded (and felt) similar to when you get stuck inbetween gears but it is a singlespeed so that rules that possible reason out. Annoyingly the noise isn't there when I get off the bike and spin the wheels or turn the crank. The noise still occurs when I am not pedalling, and there are no obvious visible loose parts colliding or rattling. The clunk does not occur in time with the wheel revolutions, so I'm pretty sure it isn't something hitting one of the spokes etc.

It sounds like something is about to break but I can't for the life of me find the source of the problem. I'm hoping that at least I make it to the weekend when I will have time to dismantle / clean / reassemble the bike, but in the mean time does anyone have any ideas what it could be?

The bike is a Wilier Tony Bevilaqua singlespeed.

Thanks

The Rookie

When/where does it occur, sounds like a pedal or BB bearing in which case it will usually occur in the same point of crank rotation and not when unloaded.

JayKosta

Check the wheel rims for side-to-side movement - looseness in the hub bearings.
Also check the fork and headset for looseness - apply front brake and attempt to roll the bike forward & backward.

Jay Kosta
Endwell NY USA

owenlars

Go straight to the oracle

http://sheldonbrown.com/creaks.html

Benjo74

From my diagnostic fiddle, I think it is looseness in the rear hub bearings. I have temporarily fixed the problem by riding my other bike, but I need to figure out how to fix it properly and didn't get chance this weekend. Thanks for the tips.

Benjo74

Rear hub bearings tightened = mystery clunk eliminated.

Thanks all!