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 harriscyclery.comharriscyclery.comOpen ↗ Hard-to-find parts shipped
Worldwide captainbike.comcaptainbike.comOpen ↗ sheldonbrown.comsheldonbrown.comOpen ↗

"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-

ike.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-

e.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: sheldonbrown.comcapacityOpen ↗

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 harriscyclery.comharriscyclery.comOpen ↗ Hard-to-find
parts shipped Worldwide captainbike.comcaptainbike.comOpen ↗
sheldonbrown.comsheldonbrown.comOpen ↗

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

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.