Part of my chain is rubbing with front derailleur.

cottonwater

I've fixed my shifting and gears so it doesn't run on the small and middle chainrings, but whenever I shift to the big ring the chain rubs against the derailleur.

I can fix this, but it only rubs for about 4-5 links and I can't move the derailleur to accomadate for this. Im guessing this either means that 4-5 links are slightly dodgy or my big chain is wonky.

My chain is perfectly oiled and relatively new so this shouldn't be the case, and so I reckon the big ring is slightly wonky, and part of it goes out further than other parts if that makes sense.. Is this a common problem. It's a low spec road bike, and shimano 2300 triple gear set so Im not expecting too much, just can't stand the grinding noise everytime I get into the big ring.

Anyone know if I can do anything without replacing the ring? If thats the case I'll replace the whole bike because its not worth so much, but I'd quite like to keep it for winter/training rides anyway.

Cheers

father_jack

Remove large chainring and refit it, perhaps been put on skewey, or grit between chainring and attachment, mine was like that (must have fully tightened one side first). Lightly tighten each one, a bit more equally, going opposite to opposite bolt until you reach correct torque.

cottonwater

Ahh never thought of that, should fix it.

Cheers

onbike 1939

It might be worth positioning yourself directly above your chainset and looking down on the offending chainring. If you rotate the cranks slowly you may see the ring becoming closer to the cage at one point. It is possible to true this by judicious use of a large adjustable spanner but the shop should have a tool to do the job if you wish.

cmm303

In additon to what has been said already:
If mechanism is clamped to the seat tube at the wrong height it can be over sensitive to alignment. Check Shimano website for spec sheet stating the clearance between the derailleur and large chain ring for your particular model (about 2-4mm I think for many models).

cottonwater

Sorry to bring back this topic again but I still can't fix the ring, I've looked at all 3 of my rings spinning now and none of them seem to go in a circle without bending a bit, which suggests the rings are actually bent..

If rings are bent can they be bent back into shape, or is it hopeless? Being completely skint I can't afford anything so need to do everything myself.

Once again thanks for any advice..

chrishd883

Unusual to bend one ring but three?

Are they all "bent" in the same place?
If so, is the BB axle bent?
Or is there any play in the BB?

bikedude

hey there cottonwater

as was mentioned by another member, use a large adjustable spanner...

find the point where the chainwheel gets closest to the frontmech, then fit the adjustable spanner at that point and prise it away slightly... this will stop it from catching.

cottonwater

It appears I was wrong about all 3 being bent, and it's just the Big ring.

However you mention that it might be something to do with my BB, which is highly likely as my bottom bracket has had it, ( Someone at Evans said it was disintegrating or something along those lines).

I tried to replace it properly, but after I removed the bolt from the crank, the thread was damaged from even before I got the bike and so even with my crank puller I can't get to the BB...

Or am I doing something wrong here? I tried for hours to get the crank off but the thread inside just wasn't there...

Sorry if this sounds basic, its frustrating having a bike that makes the grinding noise of death every 3 seconds.

Monty Dog

Try a fork-type balljoint splitter from an automotive shop or ask your LBS to remove cranks. Collapsed bearings would certainly cause an eccentric chainring rub.

cottonwater

All sorted now cheers