Shimano XT Deore front shifter

[FirstV8]

While doing some adjustment on the front derailleur  on my MTB i noticed  a adjustment underneath the shiftier marked A and B . Mine is set on A so i left it in place . ( What does it change ) I needed to adjust my derailleur to select the big chain ring a bit easier .  

[GazzaL]

While doing some adjustment on the front derailleur  on my MTB i noticed  a adjustment underneath the shiftier marked A and B . Mine is set on A so i left it in place . ( What does it change ) I needed to adjust my derailleur to select the big chain ring a bit easier .  

The XT shifter is for 2 blade and 3 blade setup. as far as I know the screw just enables or disables the extra movement. 

[droo]

Yup. The one setting is for 3x, the other is for 2x.

 

To set your FD up correctly, watch this.