Front Mech Mystery

mavientes

I have a problem with my front mech that is just confusing me, It won't shift onto the outer ring (it's a 3 ring chain set).
I have tried all possible combinations of adjusting the H and L screws and the cable tension at the shifter but to no avail. Funny thing is, on the bike stand, all works fine and it shifts smoothly. Put it on the ground and start pedalling and it just won't shift to that 3rd cog :?
The system is a SRAM X4

supersonic

If you take the H screw out, and pull on the exposed cable, how far does the mech move?

mavientes

I've not tried that, what exosed cable are you referring to?

Chunkers1980

Cable that has no outer. Pull it when in the gear you want on the selector, and see if the front mech shifts enough to move the chain to the cog.

mavientes

Thanks for the advice guys I have got it working now. However whilst twidling with the screws etc I noticed a few of the outer ring cogs were very slightly bent and a slight warp where they were (ponly minor, 5 cogs and only just) which may have contributed to the fault. So a Trip back to the bike shop me thinks as the bike is only 6 weeks old and no way should my outer cog have a fault like this.

nicklouse

Yes the teeth are not uniform and are not all "straight" they are different shapes different angles and some are shorter than others.

bails87

As nick says, they're meant to be like that, it helps shifting.

mavientes

ahh I know that bit, bt this is defiitley a warp and definitley mishaped, it's only the one section of 5 teeth. Only way I can derscripe it is, imagine a vinyl LP left out on the sun that starts to warp. Insread of the disc being flat you have a slight 'bulge'

cooldad

Bashed on something

mavientes

could be, got the bike booked for the shop tomorrow.

Once again guys, thanks for the advice