XX Chainring Questions & Swap with a X.0 Chainring Possible?
So I have an XX crank (39/26 156q GXP) and I need a new chainring. I know for my crank I am suppose to get the L-pin. But what is the actual difference between the L-pin, S-pin and C-pin. and why do I want a L-pin over a S-pin? And Yes I know the different pins go with different cranks(see below), but why. All the measurements look like they are the same.
Also as a curve ball: Can I just get a X.0 chainring (39T of course) and put that on there?
Part Number Description
11.6215.188.140 XX Chain Ring 39T S1 120 AL6 Tungsten Grey L-Pin GXP 10 speed
11.6215.188.150 XX Chain Ring 39T S1 120 AL6 Tungsten Grey S-Pin BB30 10 speed
11.6215.188.160 XX Chain Ring 39T S1 120 AL6 Tungsten Grey C-Pin Cannondale 10 speed
I'm 90% sure the different pins are just different lengths of the pin that sits on the outer chainring behind the crank arm. This is what keeps the chain from dropping between the crank arm and the spider and jamming in there or causing damage to the crank. If the pin is too long it will hit the back of the crank arm (this could be ground off easily to fit). If the pin is too short, the chain will be able to get past it and stuck if dropped over the outside of the big ring.
I think the Letters for them are just the SRAM code's that they created to track different pins through production. I bet they have many more lengths of pins beyond these for all their many cranks they make and that's why some of the letters seem arbitrary.
X0 cranks are 166q factor, not 156q factor like yours, but it's also a different crank arm shape so not sure. I'd guess the rings have a longer pin, but not sure. I really wish SRAM would put a lot more compatibility info on their website because the average shop employee has no idea cause they can't possibly know what fits where in every case. I say call SRAM and ask, but you might get the same lame response I recently got on another issue, which was go to your LBS and ask them. Customer service is a dying thing
Yeah someone had posted the pin lengths are different (I haven't seen pics), but I'm not understanding why. source: L-pin vs C-pin
I though maybe chainring spacing, but the spacing between all the XX cranks and the X0 are all the same. Then I thought maybe the chain line would be different so the pins help with different chain line, but going off Sram's measurements show the same chain line.
Sram X0: Page 15, w3 = 52.5 http://www.sram.com/sites/default/fi..._-_rev_c_0.pdf
Sram XX: Page 7, w3 = 52.5 http://www.sram.com/sites/default/fi...ifications.pdf
You are thinking about the opposite side of the chainring. The pin (singular) I am speaking of is on the outside of only the big ring. It is the one pin you see sticking up in this picture of the XX S-works spider and rings...
Please read my last post if that pin's purpose is not clear.
The shift pins you are thinking of are likely the same length because those are located and sized based on the shifting kinematics of different size gears and chainring positions. I'm pretty sure the chainring positions are the same in relation to each other on all XX and X0 (2x10). I believe the shifting features of XX and X0 rings have the same geo, just maybe very subtle differences due to different materials, but even that is likely false. They are probably exactly the same.
The outside pin, that makes alot of sense. With the different Q's if would need to be different lengths. Thank you for this info.
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