I have an Ibis Mojo fitted with XTR 8-speed shifters, and top-swing/bottom-pull XT front derail, RaceFace Turbine LP cranks and a 110mm UN72 square taper BB. Cables are coated Avid FlakJacket's.

I can't seem to get the chain to drop down into the granny gear when I'm out on the trail; I can barely get it to do it on the stand. I've taken everything off and started over from scratch twice, doing a textbook install, yadda, yadda. I've messed around a lot with the cage alignment, too.

The trouble seems to be that, even with the low-limit detent adjustment screw backed out all the way (and essentially no tension in the cable) - the derail cage is still too far out away from the frame to force the chain down to the small ring from the middle ring. This might suggest that I have the wrong size BB spindle, but I have a 110mm, and RaceFace says I can go with either 107mm or 110mm. Visually, the rings are pretty close to the chainstay - so 110mm seems about right. Middle/big ring shifting is jiggy - and the chainline looks good.

I wonder if I somehow have an incompatible front derail? I don't recall the histroy of the front derail, whether it came off my old bike or I ordered it new, but maybe it's a 9-speed and 8/9 fronts are incompatible?

Your thoughts are appreciated, thanks!

Dave