chain rub- stupid novice question

G rock

hi all,

sorry if this has been covered before, but as you can tell from the nature of the problem i'm a complete newcomer to all this!

have been out on new bike for past fortnight, and notice that the chain rubs off front derailleur in certain gear combos.

is this just a consequence of using the wrong gear combos (cross-gearing-is that the term?) or does front derailleur need adjusting?

have been watching tutorials on how to do it but a bit apprehensive about f**ing the thing up!

all help much appreciated!

CheGuedara

Sounds like a simple matter of cross chaining alright - simple error to make and frequently made by riders of all levels of experience.

Just try and avoid using the 2/3 largest cogs when in the large chainring and the 2/3 smallest cogs when in the small chainring. When you find yourself doing that see if you can find an alternative combination in the other chainring.

FISMA

As time goes on a little chain rub now and then is something that I have learned to live with.

However, to answer your question, no, chain-rub is avoidable.

As long as your ride is either new or no parts are bent, the chain should not rub the derailleur on a properly set up ride.

The problem usually occurs when the chain is at the max angle: little chain ring -> smallest casette (high gear) or big chain ring to biggest casette (lowest gear).

What setup are you riding? Is it new? Ensure that the derailleur cable is run through the front derailleur properly. How are the cables?

carthoris

Hi,

also trimming might help a little. This means you can move the front deraileur a small amount on the fly which gives a little bit more range.

http://www.sheldonbrown.com/derailer-adjustment.html#trimming

G rock

yeah to be honest it tends to happen when i'm using small chain ring and higher gears/ big ring lower gears. bike's new, tiagra mech front and rear and (the purists among you can look away now...) a triple- just don't have the legs for hills and needed the extra help!

thought maybe i was cross chaining but was surprised that it could happen in 2-3 cogs for a chain ring.

will keep an eye out for it from now on.

as regards trimming, that's something i can do while pedalling right?

took a look at cables and all seems to be ok (to my untrained eye of course)

carthoris

Yes you can trim on the fly.

As the bike is new and you are on Tiagra I imagine you change gears with the same lever as the brakes.

If you are just after changing to the big chainring and there is some noise very slightly press the lever that you use to change down to the middle ring. This should produce a click and the front deraileur should move slightly to the left, enough to stop some chain rub.

The same applies in reverse - after changing to the smaller ring a slight push on the lever that puts it into the next larger ring should trim it.

This will help but it is not likely to solve the chain rub at the more extreme gears.