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XT front derailluer compatibilty w/...(10 posts)

XT front derailluer compatibilty w/...Mitch2
May 22, 2003 6:41 PM
Ultegra cranks. Seems like I am having clearance problems w/ it.Currently it has 46/39 chainrings. When I shift it to the big ring, the inner derailluer plate will rub the small ring while the outer derailluer plate seems fine w/ the big ring. Is it possible that the XT derailluer is a tad bit narrower than a Ultegra front derailluer?

Thanks
re: XT front derailluer compatibilty w/...atpjunkie
May 22, 2003 6:49 PM
should be okay as I've run XT w/ 46 rings on MTB's. Ult. crank has a narrower profile so swing shouldn't be an issue. there are alot of Campy crossers that runXT's up front.
See if you can find the problem:)Mitch2
May 22, 2003 7:36 PM
Let me know what you think guys...As you can see the outer and inner plates are rubbing both rings...
big chainring clearancebk19
May 23, 2003 10:14 AM
How much clearance above the 46T ring do you have? Normally, with the derailleur shifter to the big ring, the outer cage plate should be 1-3mm above the ring (IIRC). If it's less than this, that might be why you are hitting the small ring. If it is the case, try mounting the derailleur slightly higher on the seat tube in order to get the necessary clearance.

Also, is the outer cage plate aligned above the big chainring when shifted to the big ring? If not, use the limit screws to set the cage plate in line with the ring. It looks like from the picture it might be a little outboard of the ring. Maybe bringing it in will give you the clearance on the small ring.

The only other thought I have, and I don't think that this could be the case, is that the gap between the chainring sizes is too small. Most mtb cranks have a 10-12 tooth jump between rings, while this only has a 7 tooth jump. Could be that what I said above, having the 1-3mm gap, actually causes it to hit the small ring. Since this isn't that uncommon of a chainring combo on a cross bike, I wouldn't think that this is the case (hey, others have gotten it to work somehow).
What is that gizmo that....Mitch2
May 22, 2003 9:16 PM
will make a bottom pull deralluer work on a cross bike w/ top tube routed cables? Where can I buy those things?

Thanks
re: XT front derailluer compatibilty w/...dpb
May 23, 2003 8:20 AM
Mitch,
Could it be a problem with the 'maximum capacity' of the deraileur? How mechanically inclined are you with regards to making the adjustments (limit screws, etc). Are you using integrated shift-levers?

I have a specialized m4cx frame with top routed cables. The stock bike is spec'd with an XTR FD and crank. That's no good for my setup, I had a 42-52 road crank. I had to get an OLD SCHOOL XT front deraileur that was built for STANDARD chainrings not compact (circa 1998?). It ran the 52 just fine.

Hope this helps, any questions just post back!
Cheers,
Damian Bradley
Found what I need but where to buy it?Mitch2
May 23, 2003 9:30 AM
Did some search and found a adaptor called the Mech-Vert but can't find it. Now going back to the adjustments. Yes, I am pretty mechanically inclined but I think the problem might be the XT triple derailleur being used on a Ultegra double crankset. I was using the same front derailleur w/ a MTB crank for years but decided lately it is time to upgrade. The clearance between the cranks and the outer plate is also an issue. My plan right now is to buy a double specific road derailleur and get that adaptor that will make it work w/ a top tube routed cable.(If I can find that darn adaptor)
Found what I need but where to buy it?The Walrus
May 23, 2003 12:50 PM
I cobbled together my own, using the pulley (and the screw and bushings) from a Travel Agent, plus an E-clamp from QBP. The E-clamp is just a clamp with a threaded boss, used to secure the bottom bracket-mounted XTR front derailleurs. Just be sure to get the right size clamp for your seat tube, don't overdo the tension on the cable (should be just enough to the pulley turn; you don't want so much tension that the cable drags) and rotate the clamp so that the cable run from the pulley to the derailleur approximates the path it would take if it were actually routed under the bottom bracket. Incidentally, this is
i exactly
what the Mech-Vert turned out to be when I saw it in an Australian QBP catalogue...
I tried the online QBPMitch2
May 24, 2003 5:16 AM
search but I can't seem to locate the product or the manufacturer. I was wondering if it has a different name here in the US. If worst comes to worst I will do exactly what you did and make one instead.
I just looked at the Australian website that originally had itThe Walrus
May 24, 2003 5:19 PM
but couldn't find the item. (www.dirtworks.com.au, if you want to give it a try...) I e-mailed them to ask if this thing's still available, but even if it is, getting it from Australia would have to be more trouble (and expense!) than just doing it yourself.

Incidentally, these are links to threads on this topic on the board...

climbo "Front Der. choice for CX bike with top pull cable" 9/3/01 4:15pm
SandiaSS "STI Question..." 6/25/02 1:51pm
Jenseman "My first cyclocross bike (Cresta)" 10/18/02 9:28pm
B2 "Top Pull FD (for road cranks)" 11/21/02 11:27am