Clunk when pedalling

othello

I'm expecting this might be a tricky thing to work out without the bike in front of you, but someone might have a bright idea!

My sons track bike is making a loud 'clunk' sound when pedalling. The noise is made worse because the frame (an aluminium Giant track frame) is amplying the sound somewhat. But something is clunking.

I've spun the pedals on the stand and nothing is catching, and the sound isn't coming from the same crank arm position every time. It seems to be a bit random.

Could it be the bottom bracket? Or is this something fixed specific (this is only his second track bike and I don't have a huge experience with them)?

jscl

Have you considered that it might be water? Sounds daft, but have seen it many times. If the bike is exposed to rain, water can get in to the BB area and often create a sound when being ridden.

othello

JSCL wrote:

Have you considered that it might be water? Sounds daft, but have seen it many times. If the bike is exposed to rain, water can get in to the BB area and often create a sound when being ridden.

I removed the seatpost and tipped it up and no water. The bb has a small hole underneath, and the bb is a sealed unit.

I'm wondering if I have the chain too tight. I'm terrible at getting the tension correct. Either too tight or too loose!

jscl

othello wrote:

JSCL wrote:

Have you considered that it might be water? Sounds daft, but have seen it many times. If the bike is exposed to rain, water can get in to the BB area and often create a sound when being ridden.

I removed the seatpost and tipped it up and no water. The bb has a small hole underneath, and the bb is a sealed unit.

I'm wondering if I have the chain too tight. I'm terrible at getting the tension correct. Either too tight or too loose!

You want it just slack enough that the chain doesn't come off, JUST. That's how the squad guys are riding it.

The slacker it is, the less resistance. It is possible that it is the chain being too tight. This just nackers your hub out and can make a grinding sound. But don't forget that that chain might have a tight spot in it too. So when you check tension, check a full rotation of the chain.

othello

Problem sorted. The chain was too tight. I loosened the wheel nuts to release the tension, and tightened up. Spun the pedals and no noise.

Thanks for the tips. An obvious one in the end.

oldwelshman

also check chain alignment, may need spacer