XTR sprockets

1. At the Shimano web site the rear derailleurs (RD-M960) are specified to
service a 11T minimum and 34T maximum sprocket and 22T maximum
front difference. All this information is clear to me, but I do not
understand the specification called "Total Capacity" (43T for SGS and 33T
for SG). I understand that SGS (the derailleur with super long arm) can take
up more slack than the SG (long arm) and also can handle a larger rear
sprockets, but what does the notation 33T and 43T actually refer to?

2. In all groups from Deore to Deore XT there is always a crank
and a front derailleur that can be used with a maximum 48T front sprocket.
On the XTR, however, (M960 series) there seems to be no option to
fit a larger than 44T sprocket on the crank and the front derailleur
FD-M961 can only service a 46T sprocket. Is this right or am
I missing something? Is there a FC-M961 crank around the corner?
I will build a no-compromise cross/hybrid with 700C wheels and 11-34
rear sprocket and 26-36-48 crank and am considering the XTR group M960.
Do I really have to stick with XT if I shall get my favorite gear ratios?

Erik L
(antispam: replace "com" with "no" in my e-mail address if you want
to communicate with me directly, not recommended if you
communicate about a news topic.)

Erik Lindeberg wrote:
1. At the Shimano web site the rear derailleurs (RD-M960) are
specified to service a 11T minimum and 34T maximum sprocket and 22T
maximum
front difference. All this information is clear to me, but I do not
understand the specification called "Total Capacity" (43T for SGS and
33T for SG). I understand that SGS (the derailleur with super long
arm) can take up more slack than the SG (long arm) and also can
handle a larger rear sprockets, but what does the notation 33T and
43T actually refer to?

total capacity = (largest chainring - smallest chainring) + (largest
sprocket - smallest sprocket)

See http://www.sheldonbrown.com/gloss_ca-m.html - Capacity

note: "Competent riders can considerably exceed the official rated
capacity, since they will not misuse the granny ring by running it with
the smaller rear sprockets, so it doesn't matter if the chain hangs slack
in those gears"

~PB

"Pete Biggs" wrote in message
news:c5dqcn$fqkc$1@ID-
but what does the notation 33T and 43T actually refer to?

total capacity = (largest chainring - smallest chainring) + (largest
sprocket - smallest sprocket)
See http://www.sheldonbrown.com/gloss_ca-m.html - Capacity
note: "Competent riders can considerably exceed the official rated
capacity, since they will not misuse the granny ring by running it with
the smaller rear sprockets, so it doesn't matter if the chain hangs slack
in those gears"

Thank you, so I will need a capacity: (48 - 26) + (34 -11) = 45.
Despite I consider myself to be a fairly competent rider I will
need the extra-long arm (SGS).
Erik

"Erik Lindeberg" wrote in message
...


2. In all groups from Deore to Deore XT there is always a crank
and a front derailleur that can be used with a maximum 48T front sprocket.
On the XTR, however, (M960 series) there seems to be no option to
fit a larger than 44T sprocket on the crank and the front derailleur
FD-M961 can only service a 46T sprocket. Is this right or am
I missing something? Is there a FC-M961 crank around the corner?
I will build a no-compromise cross/hybrid with 700C wheels and 11-34
rear sprocket and 26-36-48 crank and am considering the XTR group M960.
Do I really have to stick with XT if I shall get my favorite gear ratios?

Pete already answered the first question so I'll just address your second.
The main issue for max chainring size AIUI is the radius of the cage of the
F Der. You might get away with 48T on one rated for 46T, and Sheldon on his
site describes somewhere reprofiling a cage with a dremel tool. Otherwise
if XT is rated for 48T you'll either have to use that for the FD (obviously
you can still put XTR on the rear), or consider a road FD. FWIW, I have
exactly that on my commuter bike - long cage XTR M960 on the rear and 105 on
the front with 52-42-30 chainrings. ATM the rear cassette is a 12-23, but
I intend replacing it with an 11-32 when I go touring, which was the reason
for choosing the XTR - 21 rear tooth difference + 22 front adds up nicely to
its 43T max capacity.

Remember that the M960 is rapid-rise BTW - quickest shifting is lower, not
higher.

Rich

"Richard Goodman" wrote in message
...
"Erik Lindeberg" wrote in message
...


2. In all groups from Deore to Deore XT there is always a crank
and a front derailleur that can be used with a maximum 48T front
sprocket.
On the XTR, however, (M960 series) there seems to be no option to
fit a larger than 44T sprocket on the crank and the front derailleur
FD-M961 can only service a 46T sprocket. Is this right or am
I missing something? Is there a FC-M961 crank around the corner?
I will build a no-compromise cross/hybrid with 700C wheels and 11-34
rear sprocket and 26-36-48 crank and am considering the XTR group M960.
Do I really have to stick with XT if I shall get my favorite gear
ratios?

Pete already answered the first question so I'll just address your second.
The main issue for max chainring size AIUI is the radius of the cage of
the
F Der. You might get away with 48T on one rated for 46T, and Sheldon on
his
site describes somewhere reprofiling a cage with a dremel tool. Otherwise
if XT is rated for 48T you'll either have to use that for the FD
(obviously
you can still put XTR on the rear), or consider a road FD. FWIW, I have
exactly that on my commuter bike - long cage XTR M960 on the rear and 105
on
the front with 52-42-30 chainrings. ATM the rear cassette is a 12-23,
but
I intend replacing it with an 11-32 when I go touring, which was the
reason
for choosing the XTR - 21 rear tooth difference + 22 front adds up nicely
to
its 43T max capacity.

Remember that the M960 is rapid-rise BTW - quickest shifting is lower, not
higher.

Rich
Thank you, but is it possible to put larger than 44T chainrings on the XTR
crank?
Are these rings different than those for XT?
I will take the rapid-rise challenge. Actually I have rapid-rise on my
summer house
old cross bike (Nexave 400T). It is a pain to get used to, but with the
combined
controller on M960 I hope it will be easier. It seems to have come to stay..

Erik