[sachase]

I am wondering...if the 10 spd cassette fits where the 9 spd was, and the shifters are what indexes the derailleur, and I have 10 spd XX shifters, wouldn't any sram 9 speed rear derailleur work? I am assuming the high and low stops can be adjusted to the cassette, and the shifters are what controls where the derailleur goes...then either I'm right or I'm missing something.

 

[shiggy]

I am wondering...if the 10 spd cassette fits where the 9 spd was, and the shifters are what indexes the derailleur, and I have 10 spd XX shifters, wouldn't any sram 9 speed rear derailleur work? I am assuming the high and low stops can be adjusted to the cassette, and the shifters are what controls where the derailleur goes...then either I'm right or I'm missing something.

No, the 9-speed RDs are not compatible with 10-speed shifters, SRAM or Shimano.

 

[sachase]

Yes, Mr. SuperModerator, but why? Because Sram says so?

 

[Nater]

I believe cable pull ratio is different between SRAM's 9 and 10 speed stuff.

 

[shiggy]

Yes, Mr. SuperModerator, but why? Because Sram says so?

*sigh*

NO! Because the 10-speed RDs use different geometry than the 9-speed RDs. The RDs move a different amount for the same amount of cable travel.

Same reason you can not use a SRAM RD with a Shimano shifter.

The exception is Shimano 9-speed RDs will work with Shimano 10-speed road shifters. They have changed the geometry for the mtb 10-speed so they are not interchangeable.

 

[morganfletcher]

Yeah, it's about the rate of cable pull.

http://www.pinkbike.com/news/sram-x0-ashland-detail-2010.html

The new 10 speed XO rear derailleur (as well as the XX model) uses slightly revised cable pull ratios to move it across the 10 speed cassette, but this does mean that it is not compatible with previous years 9 speed shifters.

This is interesting.

Morgan

 

[shiggy]

This is interesting.

Morgan

Old news. Travis Brown did that a Leadville last year.

If you really want to mess around, if you hookup a Campy 10-speed road shifter to a Shimano (7-, 9-speed RD it will shift perfectly on an 8-speed Shimano/SRAM cassette.

 

[sachase]

cool thanks for the explanation.

 

[Jim311]

I say try it and see what happens

 

[sachase]

so if I have to get a 10 spd rear derailleur, should I get the med cage for my 2x10 set up?

chainrings 26/39
cassette 12-36

 

[bstiff]

so if I have to get a 10 spd rear derailleur, should I get the med cage for my 2x10 set up?

chainrings 26/39
cassette 12-36

The manual that I found here says no, if you plan to use all of the cogs on either ring:

http://www.sram.com/_media/techdocsMY08 SRAM Tech Manual English.pdf

Doc says the chain capacity is 33; your drivetrain requires 37.

 

[sachase]

cool, thats what I needed to know.