Mystery sound - scientific progress goes "clonk?"

j-p.s said:

Any ideas, or ideas how I might diagnose? I would live with it but it sounds worrying, like money
emptying itself from my bank account.

Ahh... That noise!

--
Dave...

j-p.s said:

(I have a funny noise in my bike. I should start by mentioning that a decent LBS has had a look
over it and found nothing, but see at the end.)

My chain and cogs go clonk. I have a newish (four months) hybrid, kept in reasonable nick and
cleaned a month or so ago. The clonk is similar in sound to that when you engage the pedals
suddenly: a muffled metallic thud.

It doesn't really transmit as vibration into the pedals, and it's repetitive with the approximate
period of revolution of the back wheel (really the back cassette, I suppose, as when freewheeling
there's nothing).

What's bizarre is that it tends to go away when cycling downhill. This isn't a pressure on pedals
thing: small pressure uphill gives quiet clunks; medium pressure downhill gives nothing. This
intermittent nature may have foxed the LBS, as I cycled gently downhill to them.

I suspect it is pressure related even though you think only "small" pressure uphill makes the noise.
The pressure is probably less evenly applied there at least.

Could be a faulty freewheel mechanism: frewheel body (hub part that cassette fits onto) may need
replacing. These can make odd, unique and disturbing noises! If it is this, it will eventually fail
altogether, meaning you won't be able to freewheel.

Check wheels and tyres aren't fouling anything (allowing 2mm for flex). If it was in time with crank
revolution, I would suspect the cranks or bottom bracket. Chain revolution: stiff link.

Quoted message said:

Any ideas, or ideas how I might diagnose? I would live with it but it sounds worrying, like money
emptying itself from my bank account.

Could you get another cyclist-who-knows-about-these-things or someone from LBS* to ride alongside
and behind you? They may be able to pin-point the sound more clearly than you can from the saddle -
and also watch for anything wobbling!

* Alternatively, leave bike at shop and request they take it out for a proper test ride until they
experience the problem for themselves.

~PB

On Tue, 22 Jul 2003 16:44:35 +0100, Pete Biggs scrawled: ) Could be a faulty freewheel mechanism:
frewheel body (hub part that ) cassette fits onto) may need replacing. These can make odd, unique
and ) disturbing noises! If it is this, it will eventually fail altogether, ) meaning you won't be
able to freewheel.

See, this is what I thought it was, and left it with the LBS. They reported nothing, and I had to
agree that there was no noise in the 200 yards prior to reaching the LBS....

This morning by the time I got out to Sandford-on-Thames I was making a noise fit to frighten
children. I stopped and wiggled everything I could (on my bike, that is). Found it: the rear wheel
cassette was hypermobile and could be translated along its axis by about three millimetres or more.

By the time I had got to the LBS, it was much quieter and could only move a half a millimetre. But
it was under warranty and they agreed it needed replacing for free. After four months that shouldn't
happen, and they're returning it to Giant. It's now sorted and noiseless, and they put a new chain
on too, obverously.

... A very odd noise. Like having three or four (or three-and-a-half) spokey-dokeys on my wheel.
I'll remember that one, as did you 🙂 The relapses and remissions of it confused me no end, though.

J-P
--
"But we make his love too narrow/ with false limits of our own,/ and we magnify his strictness/ with
a zeal he will not own."

Colin said:

Check your pockets. I recently had a worrying "[censored]" on every turn of the pedals: turned out to
be the house key and some change striking each other. :-)

I once spent /weeks/ trying to track down an annoying rattle on my Kingcycle, which turned out to be
my watch strap....

Dave Larrington - legslarry.beerdrinkers.co.uklegslarry.beerdrinkers.co.ukOpen ↗
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Quoted message said:

Check your pockets. I recently had a worrying "[censored]" on every turn of the pedals: turned out to
be the house key and some change striking each

other.

Quoted message said:

:-)

I find it a good idea to keep some loose nuts and bolts in a tobacco case in your panniers. You'll
never hear any minor noises then!

Pete.