Bicycle Mechanics - Tire - Frame - FD clearance issue
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09-08-10, 07:57 AM
Still working on that dang Schwinn aluminum based road build...yesterday went to install a deore xt triple fd but found there's only 2.5mm clearance between tire and derailleur body:eek:. (There is only 15mm of tire/frame clearance where the derailleur mounts.)I rode it a bit, tire never touched, but that's really a little too close for comfort. So I put my sram force double fd back on, but am not happy with the performance when used with a friction schimanno bar end. Any ideas regarding a triple fd, that doesn't have rear-facing hardware/mechanics? Crankset is Schimanno Hollowtech 105RD - 50-42-30. I'm getting to the point of removing the triple and just going to a double.............
09-08-10, 08:19 AM
Those Deores take up a lot of room, to the rear. Yes there are other Shimano triples that are much more compact ... Check the Hybrid forum under some of the fender threads.
09-08-10, 08:20 AM
I've not made a study of the cage lengths of various FDs, but if you have short chainstays and the tire overlaps the FD cage with only narrow clearance when on the granny, your options may be limited.
The inner position of the cage is based on the chainline offset of the granny, the outer clearance of the tire, by it's width. A shorter cage might reduce the overlap from the side of the tire to the crown giving you more room.
Otherwise your two choices boil down to a longer spindle to move the chain line out a bit if that's practical, or resigning yourself to slightly narrower tires. You might also buy a few millimeters by fudging the alignment of the FD slightly and bringing the heel out a bit, but any more than a tiny bit will probably hurt performance.
OTOH if you rarely use the granny, you can resign yourself to keeping the wheels aligned and leave things as they are.
09-08-10, 09:14 AM
I probably needed to be 'clearer' regarding the clearance issue. There's enough clearance b/x the tire and the FD cage; the issue is the lack of forward space between the tire tread surface and the seat tube where the derailleur mounts. The tires are 700 - 2.3, so they're plenty narrow. The deore triple fd has a pretty chunky body and I suspect it was designed for mtb use?
The radial clearance is plenty, and you shouldn't worry about it. The tire isn't going to get bigger, and if the wheel becomes mis-aligned over time that'll be wobble, not hop. If later on you decide you want bigger section tires then shop around for an FD that rides closer to the seat tube, or has more of it's mechanism off to the side.
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