Old cycle has a bit of a glitch...

[domyue]

I just started cycling and using an old bike - the gears/chain are a little funny! Sometimes the chain makes a really bad noise and "clunks" when pedalling. Once, the chain even slipped off the sprocket!

A similar thing happened to a friend's bike and he said it was because there was something that needed to be adjusted in the chain (something to that effect) - He also said the bike shop fixed it in a few minutes.

I'm a complete newbie to bike mechanics, but wondering if someone can tell me what the problem might be and how to go about fixing it??
Thanks so much!!

 

[gbb]

What sort of bike dom...front or back gears ?


It could be stretched cables, but it depends what bike and what gears, although that's usually solved with an adjustment to the tensioner...this will bring the gears back into alignment.

Depending if its the front or back gears, you can see how to do it on youtube.

Come back with some more info dom.....:?:

 

[domyue]

Hi, its got 3 gears at the front (where pedals are attached) and then got 6 i think on the sprocket. Its a trek bike and it looks a little like a mountain bike (thick tires). But looks like a typical bicycle really.

It slipped off the front gears the last time the chain came off. But the "clunking" sound usually comes from the sprocket (i think).

What do I search in youtube to fix this problem?

Thanks again

 

[gbb]

Sounds like you have a hybrid perhaps dom....
MTBs usually have 26 inch tyres, hybrids have 700X32s.

There are several possibilities on the back...
'Clunking' infers a sudden noise ?
Its possible your gears are out of adjustment, and the chain is supposed to be on one sprocket, then tries to slip onto another...hence the sudden clunk as it drops onto the next gear.
Dont touch the 2 limit screws on the derailleur. Where the black cable outer connects to the back of the derailleur, there is an adjusting nut. Turn it by hand a couple of turns 'outwards'. this will tension the inner cable a bit, and may solve the problem. There is a bit more to it than that, but thats the principle.

Search Youtube for 'adjust rear derailleur'..theres a couple on there.

It could be your freewheel or freehub (depending on the bike) is slipping. Its the least likely option, but it would mean a trip to your local bike shop (LBS)

If you think it's worth it, your LBS will tell you how much to set up the gears. Its a two minute job if its a simple adjustment...but you may need new cables.

Any idea what model it is Dom..Trek 7.1FX for instance ?

 

[Keith Oates]

The other advice above is good but one other thing it MAY be is that the chain needs some oil!!!!!!!!!!!!!!!!!!!!!!!!

 

[fossyant]

Could be many problems...

Chain could be stretched and worn,
Rear sprockets could be worn (check for sharks teeth shapes)
Rear Mech could need adjusting and chain lubing etc.
Front chain rings could be worn - (less likely)
Freewheel could be about to die

In my case the commuter has just had the drive chain replaced - chain, sprockets and chain ring (I only use the big ring commuting) but it developed a clunk soon after - it's the rear freehub that's gone - getting new wheels rather than replace the freehub, as the wheels are pretty old now, and wearing out.

You will just have to tackle one issue at a time to find out what's causing it.