XTR GS rear derailer with triple?

B said:

I have an XTR mid range rear derailer on my bike with a double crank.
Can I change cranks to a 48/36/24, with a 12-25 rear cassette?
Do I need a XTR long cage, or will my mid cage work?

Yes, it will work just fine.

Sheldon "Couldn't Be Better" Brown
+------------------------------------------+
| To do nothing is also a good remedy. |
| --Hippocrates |
+------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

"Sheldon Brown" <[email hidden]> wrote in message
news:[email hidden]...
| B wrote:
|
| > I have an XTR mid range rear derailer on my bike with a double crank.
| > Can I change cranks to a 48/36/24, with a 12-25 rear cassette?
| > Do I need a XTR long cage, or will my mid cage work?
|
| Yes, it will work just fine.
|
| Sheldon "Couldn't Be Better" Brown

Teach us to fish. Can mere mortals figure out this sort of thing? Or are
the necessary mathematical calculations only understandable to those who
design wheels that are lighter than air, or real man saddles ;-)

John Rees said:

"Sheldon Brown" <[email hidden]> wrote in message
news:[email hidden]...
| B wrote:
|
| > I have an XTR mid range rear derailer on my bike with a double crank.
| > Can I change cranks to a 48/36/24, with a 12-25 rear cassette?
| > Do I need a XTR long cage, or will my mid cage work?
|
| Yes, it will work just fine.
|
| Sheldon "Couldn't Be Better" Brown

Teach us to fish. Can mere mortals figure out this sort of thing? Or are
the necessary mathematical calculations only understandable to those who
design wheels that are lighter than air, or real man saddles ;-)

Technically this setup exceeds Shimano's specs for the XTR GS
derailleur-

http://bike.shimano.com/mtb/XTR/componenttemplate.asp?partnumber=RD-M952-GS

33 teeth capacity.

48-24 = 24
25-12 + 13

Added, that makes 37 teeth total.

BUT Shimano is assuming that you will want to wrap a 48/25 combo as
well as a 24/12 combo. Both of which are very unlikely and not good
gearing practice.

If you set up the chain length so you can wrap the largest combo-
48/25- then you will not damage anything if you go to 22/12. What
*will* happen is that the cage will not be able to wrap all of the
extra chain without having to pivot backwards so far that on the
bottom of the rear derailleur the chain will be riding across *both*
pulleys, and most lilkely will be slack anyway. The noise is bad and
the slack chain rattles and shakes, but you don't break anything, and
if you have any sense at all you get out of that combo as quick as
possible,

I am more concerned by the XTR's stated maximum cog of 34 teeth. I
wonder if you can get clean shifting across a 12-25. When I used a
Deore SGS on a 12-25, I couldn't adjust the B-screw or whatever they
call it to get the pulleys close enough to the rear cogs at both the
smallest and largest cogs. I could feel some sloppiness in the
shifting which was annoying.

Then again, other people have done similar setups with excellent
results.

Dan Daniel said:

I am more concerned by the XTR's stated maximum cog of
34 teeth. I wonder if you can get clean shifting across a 12-25.

I have a bike with an XTR GS rear derailleur. I swap cassettes between
11-23 and 11-32 without any shifting problems. If anything, shifting is a
little slicker over the narrower jumps of the 11-23 cassette.

James Thomson

Dan Daniel said:

On Fri, 04 Jun 2004 22:20:27 GMT, "John Rees" <[email hidden]> wrote:

B said:

Quoted message said:

|
| > I have an XTR mid range rear derailer on my bike with a double crank.
| > Can I change cranks to a 48/36/24, with a 12-25 rear cassette?
| > Do I need a XTR long cage, or will my mid cage work?

I replied:

Quoted message said:

Quoted message said:

| Yes, it will work just fine.
|
| Sheldon "Couldn't Be Better" Brown

John Rees said:

Quoted message said:

Teach us to fish. Can mere mortals figure out this sort of thing? Or are
the necessary mathematical calculations only understandable to those who
design wheels that are lighter than air, or real man saddles ;-)

Technically this setup exceeds Shimano's specs for the XTR GS
derailleur-

http://bike.shimano.com/mtb/XTR/componenttemplate.asp?partnumber=RD-M952-GS

33 teeth capacity.

48-24 = 24
25-12 + 13

Added, that makes 37 teeth total.

See: http://sheldonbrown.com/capacity

Sheldon "Experience Helps" Brown
+-----------------------------------------------------------+
| Always listen to the experts. |
| They'll tell you what can't be done, and why. |
| Then do it. --Robert A. Heinlein |
+-----------------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

James Thomson said:

Dan Daniel said:

I am more concerned by the XTR's stated maximum cog of
34 teeth. I wonder if you can get clean shifting across a 12-25.

I have a bike with an XTR GS rear derailleur. I swap cassettes between
11-23 and 11-32 without any shifting problems. If anything, shifting is a
little slicker over the narrower jumps of the 11-23 cassette.

James Thomson

Do you make any changes in the derailleur setup when you swap
cassettes? I'm about to try this again (with an XT SGS) and hope that
the shifting is better than last time I did it with a Deore.

Dan Daniel said:

Do you make any changes in the derailleur setup when
you swap cassettes?

None at all. One cassette comes off, the other goes on.

James Thomson

I now have:
48-34= 14 front
34-12= 22 rear
___
36 total
It has no problem with this setup.
B

(remove clothes to reply)

James Thomson said:

Dan Daniel said:

Do you make any changes in the derailleur setup when
you swap cassettes?

None at all. One cassette comes off, the other goes on.

James Thomson

Yep, did it today. From a 12-32 to 12-25. Shifted fine. On an XT SGS
rear. Maybe the Deore derailleur was too sloppy, or maybe it was just
me.

Thanks.