is it compactible?

why not?

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i tried to put road bike clipless pedal on mtb? any comments? any mud clearance? hehe

The inner curve on a road FD is designed around use with a 52/53t C-Ring. A std MtB FD is designed around a 42/44t C-Ring (XTR 952/3 was designed aroung a 48 ).

Shifting will not be paticularly good as the FD cage does not contact at the right points - it might work in the stand, but not under load.

I have a 39-46 on my cycle crossbike, and it works fine.
I guess you want to use a road derailleur for double chainrings?
Most road derailleurs can only work smooth with a difference of 14t

I ride 2 x 9 on my mtb with no problems. You only have to adjust the FD right with the shifters.

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