Bicycle Mechanics - Ultegra Triple FD compatibility w LX Triple crank?

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sstokley
06-12-08, 07:42 PM
Currently swapping out my shimano 105 double crank (53-39)for a triple on my Surly Crosscheck. Will the ultegra triple FD dial in with the LX triple (48-36-26) crank I have? Or should I purchase a LX or XT FD to
increase compatibility. Thank you in advance.

sean

maddmaxx
06-12-08, 07:55 PM
I have used a 105 triple on a 26/36/48 crankset without problem. The Ultegra FD appears to have a very similar (if not identical) cage shape.

I have also used the specific LX front derailleur that was designed to go with that crank and............am presently using the combo with a SRAM X.7 Front Derailleur (that is spec'd for a 48 tooth max ring).

All seemed to work well.
evilwheel
06-12-08, 07:58 PM
ultegra triple FD has a range of 22t. the difference between your big ring and small.
48t-26t=22t. this is the listed maximum range. should work, just slide the deraileure down.

evilwheel
06-12-08, 08:08 PM
ultegra triple FD has a range of 22t. the difference between your big ring and small.
48t-26t=22t. this is the listed maximum range. should work, just slide the deraileure down.

make sure your shifter is triple.
DMF
06-13-08, 02:39 PM
You don't give us part numbers so it's hard to know, but the two cranks may not use the same BB. The 9-speed road cranks (6500) use Octalink v.1 and the Deore LX M751/751 use Octalink V.2. The two look alike but are not interchangeable.

http://sheldonbrown.com/bbsize.html#shimano

You can't swap the BBs either because the hanger tubes are different lengths.
Metaluna
06-13-08, 02:53 PM
The unknown is the chainline. What it will be with the Shimano triple you can't know until you fit it up and measure.

I've tried it on my Cross-Check. IIRC, that LX crankset has a 50mm chainline if installed per spec. I tried several road triple FD's (not an Ultegra, but a Sora triple, a Tiagra double, and a couple of Campagnolo models) and none of them had enough reach to shift to the big ring, even when I cheated a little and moved some of the spacers to the left side of the BB to bring the chainline in a bit. Mountain FD's worked fine, of course, though the Shimano ones may interfere with the rear fender on that particular frame. The OP didn't mention if he was using STI or friction shifters for the front. I don't believe STI will index properly with a mountain FD, so that may not be a workable option.

EDIT: I should point out that my experience is with the LX M581 48-36-26 crankset, which has external bearing cups (Hollowtech?), not Octalink.