All Mountain Front Mech Issue

MontyDog

Hi, just built an Azonic Avenger for my son and I have an issue with the front mech. With him sat on the bike with the correct sag, the chain fouls the lower chain guide (i.e. the flat piece of metal that joins the two sides). It is adjusted so as when directly over the outer chainring there is a 1.5mm gap. All gear shifting is fine, just the constant rubbing when he is on the 22t inner chainring. Do they make mechs with longer cages? The LBS says that they don't.
It's an SRAM x.9 front mech with a Truvative Crank and rings. Anybody any ideas?
The other weird thing is that when I use a Shiman mech, the mech wont shift out enough or in enough without reaching the limit of the mech (even with both the limit screws fully out). The x.9 works fine, but I notice that it has a longer swing arm and offers more movement both in and out? It's a Shimano 9speed rapidfire shifter on the bars.

oxocube1

It sounds like the front mech may need to be raised a little even though you have the correct measure of distance between itself and the chainring. What rear gear does the rubbing occur? Because when you are on the inner chainring you only use the lowest 3 or 4 gears depending on the cassette speed. This means that the chain should be kept tight enough so that rubbing anywhere on the front mech does not occur. If you are in the lowest chainring and the highest gear on the rear then yes chain rub is very likely because the drivetrain is not designed to work in that gear ratio.

Also your LBS is correct they do not make longer cage front mechs, only rear mechs. Some models will most likely differ slightly but generally speaking they are all the same base design.

mrmonkfinger

MontyDog wrote:

The other weird thing is that when I use a Shiman mech, the mech wont shift out enough or in enough without reaching the limit of the mech (even with both the limit screws fully out). The x.9 works fine, but I notice that it has a longer swing arm and offers more movement both in and out? It's a Shimano 9speed rapidfire shifter on the bars.

which shimano shifter, which shimano mech?

it sounds like you may have a road group mech and a mtb shifter

MontyDog

Hi, I notice that on other AM bikes they run a 24 inner and a 34-11 cassette (he's on a 22inner and an 11-34 cassette at the moment). This will probably cure the issue.
Cheers,
Kev.

cooldad

Plenty of people use 22 though, so it should work fine.

The Rookie

You've not got a double front mech on a triple?
Does it only rub on that lower plate when in the smallest gears at the rear, answer is don't!

Simon