copydex

I'm in the final stages of building up my first bike (largely thanks to the knowledgeable folks on here who've been happy to answer questions, and to the excellent archives) but have come a bit unstuck fitting my front mech.

I'm running an XT 8 speed cassette, chain and shifters, a 9 speed XTR rear mech and 9 speed XT chainset, and a Shimano FD-M736 front mech. The front mech is, I think, compatible with both 7 and 8 speeds and when fitting, requires that it sits directly above (2mm) the highest point on the chainset and paralell to the front chainring. The height isn't an issue but I don't seem to be able to get the front of the mech paralell with the front of the chainset, in fact when it's paralell when viewed from above, it is actually about 5+mm behind the front chainring.

Is this down to an incompatibilty between the mech and the chainset or am I doing something stupid? The mech is an older (it was new old stock) type and doesn't come with one of those removable plastic guide pins that the newer Shimano come with for fitting, but I wonder if I'm supposed to physically hold the mech away from the seat tube by hand, in order to check that it's paralell, until the cable is fitted, or should it just automatically sit above and paralell to the front ring?

Apologies for the slightly rambling query, and thanks to anyone who can advise,

-dex.

TallRider

cranks designed for 9-speed chains have the chainrings spaced slightly closer together, but shouldn't be a big deal. So compatibility should be fine, given that you're using an 8-speed chain with an 8-speed derailler.

I'm unclear about why you can't get the derailler cage parallel to the chainring. You mention that "it's not parallel to the front of the chainring" - but the chainring is in a single plane, and if the front derailler is parallel to the back of the chainring, it's parallel to the front of the chainring. Parallel just means that the FD is in the same plane as the chainring, not tilted clockwise or counterclockwise when viewed from above.
Also, the FD whould be slightly behind the chainring when viewed from above.

The real question is, does it shift okay? You may be over-thinking yourself here.

dbg

The front derailer won't extend out over the big chainring until it is pulled by the cable. It usually rises at the same time. You should initially position it parallel such that when pulled by the cable it will rise and extend over the big chainring clearing it by a small amount. If you are referring to the fully extended position already, it is possible that your bottom bracket spindle is too long causing the whole crank assembly to be too far away from the frame for any derailer to reach. Your inner chainring should be close to the chainstays. If it is way more that 10 to 15 mm away, you might not be able to reach the outer (big) chainring with any derailer.

copydex

Thanks for those replies - greatly appreciated.

It was me being stupid, or, as timcupery very kindly put it, overthinking myself, as the mech will happily move over and parallel to the front chainring, it just didn't sit immediately over and parallel to it without the gear cable in operation. I now understand what I'm trying to achieve (I misunderstood the Shimano instructions), and, luckily, I have already done it. The cable is now connected up and the whole gear system is operating smoothly.

I'm off for my first ride on my new bike - please keep your fingers crossed for me that it doesn't fall apart when I hit my first bump....

Thanks again,

-dex

copydex

I'm back, and no accidents or breakdowns - it's a miracle!

Thanks to all for your assistance,

-dex.