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functional/performance difference: ultegra vs. xt rear der.(18 posts)

functional/performance difference: ultegra vs. xt rear der.JS Haiku Shop
Feb 12, 2003 11:33 AM
on the shimano 9-speed bike "build in progress"...

my 'cross bike is geared ultegra triple with xt rear and 12/32. i'm happy with the shifting and have no regrets, and have ridden several 100+ mile rides on this setup. the "build in progress" will be ultegra 9sp double, and i'm thinking 39/34 in a pinch is pretty darned close to 30/27.

that said, i'm 90% sure i'll spec it out from the start with ultegra double, xt rear derailleur, and a 12/25.

the questions:

are there any functional differences between the xt and ultegra rear derailleurs, aside from the xt being able to use **all** 9-speed cassettes?

are there any drawbacks to using the xt rear derailleur versus the ultegra?

are there any bonuses i'm not yet realizing?


Feb 12, 2003 11:39 AM
There are 2 main aspects of the rear derailleur:

1. Chain take-up, largely governed by cage length. Longer is necessary for large differences between smallest and largest gear combinations. Both should work.

2. Movement plane. The XT is designed to move in a different plane, or arc, actually, than the Ultegra. The Ultegra is designed for a max 27 tooth, but the XT for 34. The XT will move down more as it moves toward the larger cogs, so that it can clear the cogs.

You may be able to force an Ultegra to work with 32 or 34 tooth cogs, but those are the design differences.

so why do we have three different derailleurs at this level?JS Haiku Shop
Feb 12, 2003 11:56 AM
if the xt is suitable and identical performance-wise, why not eliminate the ultegra pair? marketing?
So people who want a complete Ultegra or XTR kit can have itdzrider
Feb 12, 2003 12:36 PM
The cosmetic differences between road and mtb components is more than some people can handle on one bike. Would you ride wearing 2 different sox?
sure. nmJS Haiku Shop
Feb 12, 2003 12:46 PM
My wife has an XT on her Trek 5500RickC5
Feb 12, 2003 3:08 PM
Then again, she sometimes wears two different socks.

She wanted lower gears for hills, so I bagged the DA rear der and casette, and bought XT stuff. Works great, and she doen't mind the appearance.
not sameDougSloan
Feb 12, 2003 12:46 PM
If you are using smaller cassettes, the Ultegra will keep the upper pulley closer to the cogs and wrap more chain around the cogs, giving better shifting and less likely to skip.

thanks nmJS Haiku Shop
Feb 12, 2003 12:50 PM
What happens if you adjust the B screw on an XT der?dzrider
Feb 12, 2003 1:53 PM
Wouldn't that allow the upper pulley to sit close to the cogs? My suspicion is that XT or XTR derailleurs would work fine on a small cassette, just like they work fine with Ultegra or DuraAce levers.
Really?Rusty Coggs
Feb 12, 2003 2:06 PM
The xt is designed to work with an 11 tooth under tough conditions.
Feb 12, 2003 2:26 PM
As the XT moves inward, it moves down, further away from the axle, more than the Ultegra. The b screw will make it closer over the whole range.
Feb 12, 2003 2:35 PM
Path of different derailleurs as they move inward:
longer cageatpjunkie
Feb 12, 2003 2:55 PM
gives wider gear ratio but less snappy shifting. also increases chance of dropping chain on bounces etc... It's why most cxers prefer road dera. in back. less chance of a dropped chain during portage. longer cage, bigger cogs means more chain, more slap, more error
Short cage version. nmRusty Coggs
Feb 12, 2003 4:55 PM
diagramRusty Coggs
Feb 12, 2003 5:05 PM
Ok,thanks.I buy the theory and diagram,but does it really matter in practical application? I don't think I have noticd a problem.
i had an ultegra on the rear of my lemond. but i swapped it for an xt, and also changed cassettes so i'd have the wider range on the rear. it's great because it does give me a much wider range and its all i need for negotiating the hills in seattle. i didnt have to swap my double up front for a triple. BUT, i do notice that the shifting is not quite as crisp or as dead on as it was with the ultegra. its just a wee bit less precise. noticable, but just barely. probably because of the difference in the length of the two cages. the xt's longer cage just means a less precise shifting process. i guess. i really like it and would recommend going with the rear xt unit if you want that extra range, but just be prepared for less precise shifting.keeshadog
Feb 12, 2003 9:34 PM
sorry about that folks....keeshadog
Feb 12, 2003 9:37 PM
thanks, all. xt it is. nmJS Haiku Shop
Feb 13, 2003 6:03 AM