SRAM Crank Compatibility

[Divebomb]

Hi all, I’m primarily a Shimano guy, but I scored a very clean SRAM Red 10 speed group locally (for a great price) for a build I’m working on. I need a BSA/GXP spindle and this one is a BB30, so I know I need a different crank. My question is about compatibility between their 11 and 10 speed cranks. The chainrings are marked 10 speed on mine and the newer ones are marked 11 speed. My cranks Do not indicate # of speeds.

My questions:
Could I replace just the non-drive crankarm with one sporting a GXP spindle? I’m not sure if the size of the spindle interface differs (probably).

If I were to move the 10 speed rings to a Red 11 speed crank, would I have an issue with spacing, or is it the rings that determine the spacing?

I’ve been keeping an eye out for a 170 or 172.5 10 speed GXP crankset and I don’t see many out there, so I’m trying to get creative.

Appreciate your suggestions.

[Mark McM]

There's very little difference between 10spd and 11spd chainrings/cranks, and they can be used virtually interchangeably (10spd cranks/chainrings with 11spd drivetrains and vice-versa). The 10pd crank should work fine with the 11spd chainrings.

If your frame has a 68mm BSA bottom bracket shell, they do make BB cups that for BSA bottom brackets tha fit 30mm cranks, so you'd just need to find the right bottom bracket cups. SRAM does not make these cups, but other manufacturers make cups that should work with a SRAM 30mm crank.

For some of the nitty gritty:

Typically, only the chainrings are changed between 10spd and 11spd cranks, with the chainring teeth offsets modified so that the chainring teeth are slightly closer together for 11spd (a fraction of a millimeter). So 11spd chainrings could be used on 10spd cranks (and vice-versa).

You can't change the cranks between GXP and 30mm just by swapping a single crankarm, for two reasons: 1) The spindle diameter and splines are different between the two spindle types, so a GXP spindle won't make with a 30mm crank arm (and vice-versa); 2) On GXP cranks, the spindle is permanently attached to the right crank, and on 30mm cranks the spindle is permanently attached to the left crank (at least for SRAM 30mm cranks).

[kppolich]

Chainrings will be fine between 10/11sp

No on swapping just one side, they work together.
GXP has the spindle attached to the drive side. NDS arm is free.
BB30 has the spindle attached to the NDS, chainrings and DS arm is free.

[many_styles]

Originally Posted by Mark McM

There's very little difference between 10spd and 11spd chainrings/cranks, and they can be used virtually interchangeably (10spd cranks/chainrings with 11spd drivetrains and vice-versa). The 10pd crank should work fine with the 11spd chainrings.

If your frame has a 68mm BSA bottom bracket shell, they do make BB cups that for BSA bottom brackets tha fit 30mm cranks, so you'd just need to find the right bottom bracket cups. SRAM does not make these cups, but other manufacturers make cups that should work with a SRAM 30mm crank.

For some of the nitty gritty:

Typically, only the chainrings are changed between 10spd and 11spd cranks, with the chainring teeth offsets modified so that the chainring teeth are slightly closer together for 11spd (a fraction of a millimeter). So 11spd chainrings could be used on 10spd cranks (and vice-versa).

You can't change the cranks between GXP and 30mm just by swapping a single crankarm, for two reasons: 1) The spindle diameter and splines are different between the two spindle types, so a GXP spindle won't make with a 30mm crank arm (and vice-versa); 2) On GXP cranks, the spindle is permanently attached to the right crank, and on 30mm cranks the spindle is permanently attached to the left crank (at least for SRAM 30mm cranks).

Another great reply Mark! Thanks!


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[Divebomb]

Agree with the comment on the great reply, Mark. Very thorough and easy to digest- thanks for that.

The spindle on the bb30 is only 84mm long and will not accommodate the 104mm required (at least for the Wheels Mfg version) bb cup conversion mentioned. Anyone know of a different type?

https://bikerumor.com/2018/12/28/aas...ded-bsa-frame/

Originally Posted by Mark McM

There's very little difference between 10spd and 11spd chainrings/cranks, and they can be used virtually interchangeably (10spd cranks/chainrings with 11spd drivetrains and vice-versa). The 10pd crank should work fine with the 11spd chainrings.

If your frame has a 68mm BSA bottom bracket shell, they do make BB cups that for BSA bottom brackets tha fit 30mm cranks, so you'd just need to find the right bottom bracket cups. SRAM does not make these cups, but other manufacturers make cups that should work with a SRAM 30mm crank.

For some of the nitty gritty:

Typically, only the chainrings are changed between 10spd and 11spd cranks, with the chainring teeth offsets modified so that the chainring teeth are slightly closer together for 11spd (a fraction of a millimeter). So 11spd chainrings could be used on 10spd cranks (and vice-versa).

You can't change the cranks between GXP and 30mm just by swapping a single crankarm, for two reasons: 1) The spindle diameter and splines are different between the two spindle types, so a GXP spindle won't make with a 30mm crank arm (and vice-versa); 2) On GXP cranks, the spindle is permanently attached to the right crank, and on 30mm cranks the spindle is permanently attached to the left crank (at least for SRAM 30mm cranks).

[Mark McM]

Originally Posted by Divebomb

Agree with the comment on the great reply, Mark. Very thorough and easy to digest- thanks for that.

The spindle on the bb30 is only 84mm long and will not accommodate the 104mm required (at least for the Wheels Mfg version) bb cup conversion mentioned. Anyone know of a different type?

https://bikerumor.com/2018/12/28/aas...ded-bsa-frame/

So this crank is a true BB30 crank then? The later iterations SRAM road cranks that are labeled "BB30" are actually more like BB386 crank (which also happen to be able to be fit to BB30 bottom brackets by using spacers). These later iterations have spindles long enough to be fit to a 68mm BSA bottom bracket shell by using cups with external bearings.

If your crank is a true BB30 crank, then you're out of luck, it can't be fit to a BSA bottom bracket (because there is no room for the bearings).

[Divebomb]

Yep - I think that’s the deal and wanted to confirm the need to swap/buy a crankset.

Originally Posted by Mark McM

So this crank is a true BB30 crank then? The later iterations SRAM road cranks that are labeled "BB30" are actually more like BB386 crank (which also happen to be able to be fit to BB30 bottom brackets by using spacers). These later iterations have spindles long enough to be fit to a 68mm BSA bottom bracket shell by using cups with external bearings.

If your crank is a true BB30 crank, then you're out of luck, it can't be fit to a BSA bottom bracket (because there is no room for the bearings).