Is my chain too fat?

big_southern_jesse Posts: 729
edited August 2012 in Workshop
Hi folks, excuse the amateur question.

I have a secondhand Spec Allez, probably 5-7 years old. It has 2x9 Sora groupset on it. IT's all a little tired, but seems fine except when trying to ride on the smallest 2 or 3 sprockets.

There is a continual rumbling/grinding feeling. It looks as though the outer chain links rest on the sprockets on either side rather than actually dropping between them for the chain to sit on the chosen sprocket properly.

So is it the wrong chain? I am under the impression that there are different chain widths, but lacking in much knowledge. Or have the sprockets got so worn that the chain is now resting on areas that it would normally be clear of?

Any ideas?

Many thanks,

Proved by testing to be faster than a badger.
The world's ultimate marmite bike


  • There are different chain widths for the speed of the bike (e.g. if you have ten gears - sprockets - on the cassette on the back wheel you need a 10 speed chain - if there are nine then a nine speed chain). You can count the number of sprockets and the chain you have should be marked to show what speed it is. If the cassette - and/or chain - wears that does change the way the chain sits on the sprockets but (AFAIK) not really in the way, or to the extent, that you describe. Its more that the chain skips or slips on the sprockets.

    It's hard to tell without seeing your bike but is the indexing (tension in the cable that moves the derailleur ok?) if that's is wrong it could pull the chain to one side of the sprocket so it doesn't sit properly (can't think why it would end up touching both sides though as the tension pulls the chain on way or t'other).

    Also if the angle of the front deraileur is wrong that could concievably pull the chain accross at an odd angle (does it happen no matter what ring you are in at the front - small ring at front and small sprockets at rear [and vice versa] are to be avoided. Both could make the chain sit funny on the rear sprockets but you would see and hear the chain rub on the front derailuer cage much more than that.

    I would say check its the right chain first and is it is then my next port of call would be rear derailuer set up.

    Hope this helps.
  • maddog 2
    maddog 2 Posts: 8,114
    does it say anything on the side of the chain?
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • cycleclinic
    cycleclinic Posts: 6,865
    This is really something someone has to look at. Pics are not going to help much. Read park tools guide to setting up gears if you want to have ago yourself or visit a LBS that does not mind giving some on the spot help.

    It could be a worn chain and sprockets or indexing out of adjustment. To check the chain without a checker just a 12" rule and place the zero in the midle of one link and is the 12th link is 1/8" beyonf the 12" marks you chain and cogss will be worn past hope. So change both. -wheel building and other stuff.