UKC

I have problems trying to stop the chain rubbing on the change mechanism cage that pushes / pulls the chain when cahing gear, on the chain wheel set of three chain rings, despite keeping adjusting the cable length on the small lever which the cable pulls on (attached to the down tube). I have to hold the cable against the spring tension with a pair of pliers and then using the right size allen key to loosen the bolt that grips the cable, and try to find a position when re-tightened where the mech doesnt rub the chain in some gear positions, using trial and error. So far have only managed to keep the mech from rubbing the chain in thelower gears which I use mostly, in high gears (used less often on long downhills) I still get rubbing chain. There are also two screws on the mech, but having played with those they only seem to adjust a stop to prevent the chain flying off the big or small chain ring. The bike is 10 years old (Raleigh sports 300) with shimano type gear set and chain rings.

Any advice, or is it something I have to live with?

In reply to ianghogg:

I don't know, but I am glad you are asking as mine is a mess at the moment after having new chain rings put on. I'm so busy at the moment that I have just left it for now, but it is fine on the big and small rings, but on the middle ring it rubs for the two lowest gears... How can that be if it is fine for the lower and higher rings?!

In reply to ianghogg:

Here are some good online instructions with pictures...

http://www.instructables.com/id/How-To-Properly-Adjust-The-Front-Derailleur...

In reply to tlm:
thanks - instructions look really clear. I also thought of checking the chain rings to make sure all the allen bolts are tight and the mech and chain rings havn't moved , and are in line etc...

In reply to ianghogg:

I've never found it possible to prevent that happening in all gears. The extremes tend to rub i.e. big ring front, big ring back and small ring front small ring back. The goal (mine at least) is to prevent rubbing for the rest.

One thing to check is whether the mech has been hit and bent or has rotated around the down tube. If it isn't straight in line with the chain then it'll rub like a devil.

In reply to M0nkey:


I have, by taking it to the bike shop...

In reply to ianghogg:

General Info:
You should never really use the extreme opposite gear ratios, especially small front, small back. It increases chain wear and the chance of the chain coming off. With that in mind a lot of mechanics set up a bike so that it will rub very slightly at the extremes to get a better shift.

Usual causes of rubbing are your cable is too loose or tight or your limit screws (the two little screws you mention) are set wrong. if the cable is set wrong, you can usually adjust it a little bit via a "barrel adjuster" at the shifter on the handlebars or at the headtube.

Specific to your case:
If your downtube shifters are non-indexed (they don't click into place) and you can't stop the chain from rubbing then the derailleur could be twisted or bent, or maybe at the wrong height on the seat tube. Keep in mind that on a non-indexed derailleur the "shift point" may well be different from the "no rub" point. Though it sounds like you have done a lot of playing around with it.

Can you see on the derailleur cage where the chain rubs?

There is also a (small) chance that you have the wrong size of chain or derailleur.

You never have to live with a rubbing chain! Please don't!

In reply to Bob_the_Builder:

bob the expert...

So how on earth can my dérailleur be rubbing when I am on the centre ring at the front, for the lowest two gears at the back, but fine for absolutely everything else?

I've just had a new front thingy (the chain rings, pedals, the lot).

Have they just put the wrong sort on?

In reply to ianghogg: If you haven't got a barrel adjuster I'd fit something like this http://www.probikekit.co.uk/bicycle-gear-brake-cables/shimano-sm-ca70-in-li... it's all down to cable tension (provided nothing's damaged or bent) and this will allow you to make the fine adjustments you need. Like others have said it's almost impossible to eliminate it in all gear configurations (especially with a triple, I've always found triples to be such a faff I never use them) but to get it shifting sweetly without the two extreme ratios rubbing is probably the best you can hope for.

In reply to andreas:


It's equally, if not more, likely to be due to incorrectly adjusted limit screws (as Bob_the_Builder mentioned) or the derailleur cage being out of alignment. A barrel adjuster can be a useful thing to have anyway, but it won't fix the problem if cable tension isn't the cause.

In reply to tlm:

That's a tricky one!

Maybe the chainring is bent? Seems unlikely though...

There are so many things that could be affecting it, but maybe have a bit of a fiddle around with the rear derailleur barrel adjuster. Quarter of a turn either way and see if that helps. If not I can't help much over the winternets I'm afraid.

If the rubbing is not constant that would suggest something is bent but there is always something a little out of shape on all but the best maintained and/or least ridden bikes!

In reply to Bob_the_Builder:

I took it to the free bike man today - the chainrings (well, that whole front bit including the pedals) are new and it started rubbing after they were replaced. He said it was cos the front mech is old and worn and a bit wobbley - I've only had the bike 2 years!!!! So then he changed his mind and said it was cos I ride it so much! HA HA!!

Anyway - he is going to get a new front mech for me and in the meantime has adjusted it so that it rubs in less annoying gears.

Thanks for your kind reply - it's nice to have someone make some suggestions.

In reply to tlm:

No worries, I like to tinker with bikes! I used to me a mechanic and always got in trouble for trying to teach people to fix their bikes rather than make them pay for it...

FYI, "the whole front bit" is a lot of different bits! The bottom bracket is the unit containing the bearings and attaches them to the frame, the cranks go from the bottom bracket to the pedals, and the chainrings are mounted on the cranks. There are myriad different bottom bracket configurations and they each have their own method of attaching to the cranks.

It sounds like your guy knows what's up, I hope it works out. Remember to lube your chain regularly and try to sort things out quickly, or more expensive damage can occur.

In reply to Bob_the_Builder:


Yeah - I'm quite good about doing stuff, but I don't really enjoy doing it - we don't have a really good space for doing it and I just want it mended. That's why I didn't fiddle with the gears - I know how I might make them worse and I thought it was a bit weird. I do own a chain whip! But we have a thing at work at the moment where some bike guys come once a month and do everything for free, so I have been making the most of it!!

But there are lots of good web pages/videos now that tell you how to do stuff and give all the handy tips!

In reply to tlm:

http://www.parktool.com/blog/repair-help
http://sheldonbrown.com/

Best resources I know of, parktool for modern bikes and Sheldon Brown for more... esoteric stuff...

The parktool site even links to the tool to buy it! Whee! Though I reckon Park are the best so if you're going to buy a tool it might as well be from them.

If you read Sheldon Brown's site too much you'll suddenly realise your house is full of weird old bikes and you can't remember how they got there. You have been warned.