front mech problems

nato

Hi guys.
after some more help!
Ive started upgrading some bits on my scott one of which is a shimano XT 770 front mech.
I just cant seem to get it right but im now starting to think can i run this with an internal bottom bracket chainset or does it need to be mated to an external bb chainset?

Im pretty sure ive set it all up right and ive double checked everything so thats the last thing i can think of.

Anybody else come across this problem?

Cheers guys and gals

supersonic

What exactly is the problem though?

What was it replacing?

nato

the original was a shimano deore (factory spec cheapo)
problem is im setting it up with the shimano "pro set up" sticker and wedge and all looks well but once the wedge is removed the adjester screws have no effect and the inside of the mech arm is very tight against the chain when in middle and top sprocket.
When on bottom sprocket the distance between the chain and inside of mech is around a cm and like i said the adjuster screw has no effect.
it seems as tho the chainset needs to be futher away from the frame which im guessing on an external bb it would be!!

supersonic

The chainlines with external BB are roughly the same, you can make minor adjustments with the spacers provided.

Is the cable tension tension correct? You need to start buy setting the L limit screw with no tension at all whilst you are in the largest rear cog and obviously small front chainring. Adjust the L screw until the chain just clears the inside of the plate. Add tension until it shifts cleanly to the middle, and cleanl;y back down.

Then you can work on the H stop. This limits how far the mech can move over.

Also need to makes sure the angle is correct.

supersonic

Also remember that using the big chainring and big rear cog is not recommended due to the angle of the chain. You can get the same gear in the middle chainring ie:

44/32 roughly equals 32/23 or so.

same for small rear cog and small front chainring.

nato

yeah ive been doing it with the right chain ring to sprocket combo. il have a go tomorrow night with your advise and see how i get on, il let you know what happens, thanks for your help so far.

supersonic

They can be really fiddly, took me quite a while to get the knack!

You'll get there! Just remember for the H limit stop to do anything, the cage must reach it - which requires tension. It is just a stop - the L stop is for the return spring which is why you set it with no cab;e tension.

nato

just finished fine tuning and just wanted to say your advise was spot on.
thanks for your help no doubt il be needed more soon!!
Thanks again.

supersonic

Nice one!