Chain Rub

maklabouhlel · 20 Feb 2016 at 10:56

Hi, my road bike has extreme chain rub with front derailleur when in outer big ring at front and outer three smallest rings at back. Bike shop said this is normal and I should avoid these three rings. Is this true?

saitrix · 20 Feb 2016 at 11:03

Not at all they are fobbing you off, when you are setting up the limit screws on derailleurs you move the front onto the big ring and the rear to smallest cog. Then from there you alter your high limit screw. To do that you pull on the gear cable manually and see if it moves outwards more, if it doesn't then turn the high limit screw anticlockwise until it only just doesn't rub the chain. The best thing to do is either take it somewhere else if you aren't confident or follow the below instructions.

http://www.parktool.com/blog/repair-help/front-derailleur-adjustment

Vonhelmet · 20 Feb 2016 at 12:26

Big ring front, small sprockets back? That shouldn't cause chain rub. Otherwise when would you ever use those small sprockets? That's nonsense.

maklabouhlel · 20 Feb 2016 at 12:52

saitrix said:
Not at all they are fobbing you off, when you are setting up the limit screws on derailleurs you move the front onto the big ring and the rear to smallest cog. Then from there you alter your high limit screw. To do that you pull on the gear cable manually and see if it moves outwards more, if it doesn't then turn the high limit screw anticlockwise until it only just doesn't rub the chain. The best thing to do is either take it somewhere else if you aren't confident or follow the below instructions.

http://www.parktool.com/blog/repair-help/front-derailleur-adjustment

Thanks for that. Actually, when I manually pull the cable it does move out more, clearing the rub. Should I increase the cable tension then? Cheers.

saitrix · 20 Feb 2016 at 16:39

Yeah first of all pull the cable and get the end adjustment correct so that way the chain won't fall off. Then just increase cable tension and you are done! The only other thing to do is check you have only a small gap on the small ring and big cog to minimise the chance of a dropped chain.

DaleTheWhale · 20 Feb 2016 at 17:05

maklabouhlel said:
Hi, my road bike has extreme chain rub with front derailleur when in outer big ring at front and outer three smallest rings at back. Bike shop said this is normal and I should avoid these three rings. Is this true?

Funnily enough my local LBS said the same thing when I had an issue jumping from the small to big ring, the guy was an idiot, as he decided to then lecture me for 30 minutes on cross gearing and that "I am wreckless" to ride that way and should expect my chain to fall off regularly. Needless to say, I just manually adjusted my dérailleur myself and it's now fine.

Some fine tuning by yourself and the rubbing will stop.

maklabouhlel · 21 Feb 2016 at 11:37

saitrix said:
Yeah first of all pull the cable and get the end adjustment correct so that way the chain won't fall off. Then just increase cable tension and you are done! The only other thing to do is check you have only a small gap on the small ring and big cog to minimise the chance of a dropped chain.

A single turn of the barrel adjuster sorted it. Can't believe it was that simple. Thanks guys.