Bicycle Mechanics - clunking from front mech
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05-03-10, 02:37 PM
I'm after some help if anyone can...... me and my son are new to road biking, and my sons bike has developed a problem....
I bought his bike second hand, it has worked fine for a few months but has now developed a knocking / clunking noise that seems to be coming from the front mech...... it's not the sound that it makes when it is trying to change gears, it sounds much worse.....
It happens in all gears but only at higher speeds when the bike is under more stress..... he is running shimnano 105 front mech with sora rear...
05-03-10, 02:46 PM
The front deraillaur only touches the chain when shifting (ideally), so if the noise occurs while not shifting and there's no rubbing (such as when in the middle of the cassette/freewheel in the rear), I don't think it's the FD.
My first thought is it could be the pedals. Grab one at at a time and try to move it around against the spindle. Do you feel any play in either?
It might also be the bottom bracket. Grab the end of one of the crank arms and push and pull it toward and away from the frame. Feel any play?
05-03-10, 03:04 PM
it's defo not from the deraillaur like you say... and doesn't sound like the chain rubbing at all....
I did a quick check of the pedals too as this was my first idea, couldn't see any play but will double check it 2moro when it is light, and your bottom bracket idea......
If it is the bottom bracket like you mention, can that just be tightened up or will it need replacing.... many thanks for your help buddy, greatly appreciated
05-03-10, 04:07 PM
Depends on the bottom bracket type.
If it is a traditional spindle and cup bottom bracket, then the cups may be able to just be adjusted.
Newer cartridge or outboard BBs should just be replaced.
05-04-10, 11:42 AM
Thanks for your help jive turkey, you were correct with the bottom bracket being worn, there was slight play in there and this was confirmed by the local bike shop who is now replacing the bracket.....
Many thanks for your advice
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