Front Derailleur Woes

[AndyPeace]

Additional:

• Not a limit screw issue, the bottom limit screw has a few turns more of adjustment that don't do anything because the derailleur has bottomed out on the frame.
• Not a cable tension issue, the cable is removed at this point
• The derailer runs parallel to the chainrings, it doesn't appear to be twisted in any way
• Someone else suggested measuring distance from the inside of each crank to the seat tube to see if the crank assembly is centred

ta

I'd imagine putting shims on the chain rings will cause problems, like creaking and alignment issues which could derail your chain. Have you tried removing the derailer and re-fitting it yourself, or asking at the lbs, I doubt they would ask for much to do this.

 

[thedatastream]

Suggestions from the Triban 3 Owners Forum:
Adjust bottom bracket centering by loosening one side then tightening the other
Shimming crank on chainring side
Going to look at this after Tuesdays ride

 

[raindog]

How can you "shim a crank"? It's tightened onto the square taper, and that's it. Can't see how it can be shimmed. This all sounds a bit dodgy.

 

[Widge]

I have been getting chain rub on my Triban 3 (stock, unmodified) when in smallest front chain ring + biggest rear sprocket on the inside of the front derailleur (i.e. lowest gear)

I attempted to adjust the limit screws on the front derailleur to compensate but they only adjust so far. Why?

Because, as the OP pointed out, the spring for the front derailleur spring rests on the frame and prevents the full range of motion inwards.

Therefore chain rub seems inevitable when in the lowest gear (necessary for West Yorkshire hills!). This is an unmodified Triban as supplied by Decathlon although I have done plenty of miles on it.

Other than buying a new front derailleur that fits better the only thing I can think to do is to shim the chain rings outwards slightly to adjust the chain line at the front? Another 0.5mm ~ 1.0mm ought to be enough.

Sound reasonable or should I be looking elsewhere?

Cheers.

p.s. I haven't measured the chain line yet.

Hi Data,

I know exactly what you mean.

The main d/r return spring sits uncomfortably close the frame when you are in the granny ring........you will notice that the designers thought this through somewhat and have incorporated a depression in the tube to accommodate it.

When I fettled my Triban front mech I was conscious of this tight clearance - BUT - I have to say, I have managed to set it so that the chain runs without scraping the mech in the lowest gears and the spring doesn't collide withe frame. Whether it is because I have just managed, through trial and error, to set the angle and height of the mech at its optimum, I'm not sure........but the mech spring clears the frame by a gnats whisker (set by the limit screw) and has not altered its position or needed resetting ever since. Clearly - it CAN be done if you persist. I have shimano wheels too and didn't experience any need to change the front set up.
The rear was a different matter, however..........good luck.,,,and I HTH?

best

w