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Dura ace double front shifting with Ultegra triple rear d?(9 posts)

Dura ace double front shifting with Ultegra triple rear d?eflayer
Mar 1, 2003 6:12 PM
I am trying to avoid going to a triple on my DA double bike.

What tooth range of a cassette can you use with DA double cranks and double front derailleur and an Ultegra triple rear derailleur. For a big cassette do I have to go to a mountain rear derailleur or will an Ultegra triple work?
Ultegra/DA cassettes go until 12-27, I think 28 works tooPeterRider
Mar 1, 2003 6:54 PM
re: Dura ace double front shifting with Ultegra triple rear d?Rusty Coggs
Mar 1, 2003 6:55 PM
An ultegra long cage has the same large cog spec of 27 as the short cage,but it might shift a 30 ok.The front should handle a 48 large ring,but the smallest small ring you can use on the 130BCD is a 38.
the real question: 30 tooth cog & DA double crank? which rear d?eflayer
Mar 1, 2003 9:06 PM
I need to go to at least a 12-30 or 13-30 cassette to get low enough gears. If I stay with DA double up front, can I use a road rear derailleur or do I have to go to xt or xtr?

Thanks,
Eddie
Ultegra triple rear der. w/ 34T cogTony Montana
Mar 4, 2003 3:34 PM
On my cross bike I'm running an XT 11/34 cassette and an Ultegra triple rear der. I've put almost 1500 miles on it with no problems.
re: Dura ace double front shifting with Ultegra triple rear d?johnnybegood
Mar 2, 2003 8:45 AM
All following info is available on the Shimano website. Double front deraileurs for both DA and Ult are the same: will handle a large chainring between 50T and 56T with a max difference between largest and smallest chainring of 15T. Front triples are a little different: DA is 53T max chainring, Ult is 52T; max difference is 23T for DA and 22T for Ult. All four double rear deraileurs have a range of 11-27T. Total capacity (chainring difference plus cassette difference) is 29T for both the double front deraileurs (SS models) and 38T for the DA triple and 37 for the Ult triple. With this info you can figure out which models you need for what you want to do.
The front end is fine....TFerguson
Mar 2, 2003 4:21 PM
Your current double on the front is fine.

For the rear: to use a 32 to 34 tooth mtb cassette (Shimano standard road only go up to 27) you will need an mtb rear derailleur. XT or XTR are fine. Deore or LX will also work.

The problem is the amount of slack chain that the pulleys need take up when you go from the largest (ie. 32 or 34) to the smallest (ie. 11 or 12). The road derailleurs just don't have enough to handle more than a 27 tooth to 11 tooth drop.

Other combinations may or may not work depending on your mechanical expertise and patience at setting them up, but the above is fairly standard and does work.

TF
Your Ultegra triple may be already me optimal unless...pusher
Mar 3, 2003 2:34 PM
There is some difference between road and mountain rear deraillers with the positioning of the top pulley when in the lowest gear. It isn't the parallelogram swing angle; that would change cable pull. Cable pull is the same.
In terms of capacity, you are all set.
My setup: 105 double, 12-32 XTR 8 speed, and 105 double rear mech. I do use the big-big, but I avoid the small-small which results in chain-sag. Less than ideal. I am just getting by untill I can afford an XT long cage.
A Shimano MTB medium cage (GS) would be Ideal for you; unless, like me, you find that 39-32 or 34 (for you 9 speed folks) is still not low enough, and plan on someday getting a tripple. In that case, save $9 dollars with the long cage and be on the safe side.
When I am in my lowest cog, the upper pulley teeth hit the cog teeth. Forward peddaling results in a small bit of clearance, but backpeddaling makes an unhappy sound. MTB rear mechs shouldn't do this even on a 34. But, I don't know that they don't.
I hope that answered your questions.
correction: Your Ultegra triple may already be optimal unless...pusher
Mar 3, 2003 2:35 PM