Sram Red BB386 crank arm compatibility

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Jian81
Posts: 36
Joined: Mon Jun 15, 2015 1:29 pm

by Jian81

Hi guys i have a question regarding the BB386 left crank arm and its compatibility with a regular sram red 22 bb30 crank spider. I bought a Sram Red 22 BB386 Quarq ready crankset as i needed the left crank arm to fit my BB86 frameset that accepts a BB30 spindle(couldnt find anyone selling just the left arm).
I was wondering if the left BB386 crank arms is able to fit into a regular Sram red 22 BB30 crank spider without issues? Reason being is that i have the BB30 crankset with 52/36t which i favour largely and want to reuse that crank spider. My BB386 crankset is a 53/39.
I know that the only difference between the BB386 and BB30 version is that the left crank spindle arm is longer width wise for the bb386 version to fit into a bb386 frame, and the BB386 is also quarq power ready, correct me if im wrong.

Any help would be greatly appreciated! Cheers!

Hexsense
Posts: 517
Joined: Wed Dec 30, 2015 12:41 am

by Hexsense

Jian81 wrote:Hi guys i have a question regarding the BB386 left crank arm and its compatibility with a regular sram red 22 bb30 crank spider. I bought a Sram Red 22 BB386 Quarq ready crankset as i needed the left crank arm to fit my BB86 frameset that accepts a BB30 spindle(couldnt find anyone selling just the left arm).
I was wondering if the left BB386 crank arms is able to fit into a regular Sram red 22 BB30 crank spider without issues? Reason being is that i have the BB30 crankset with 52/36t which i favour largely and want to reuse that crank spider. My BB386 crankset is a 53/39.
I know that the only difference between the BB386 and BB30 version is that the left crank spindle arm is longer width wise for the bb386 version to fit into a bb386 frame, and the BB386 is also quarq power ready, correct me if im wrong.

Any help would be greatly appreciated! Cheers!
Yes you are wrong.
Both left and right side are different.
Left arm of BB30 are more tapered in to provide more heel clearance. Excluding adjuster, there is no other spacer for bb30 bb.
Left arm of BB386 are more straight because it need to clear wider bb. When use on BB30 BB, it need additional spacer.

Right arm of BB30 are one piece, tapered similar to left arm. If you look how Sram Red BB30 sit on a BB30 BB, you'll notice that it sit flat touching the BB WITHOUT any spacers.
Right arm of BB386 are modular, it contains arm and spider separately. Arm is more straight (not dive in to clear your heel) and spider sit further out from the frame (and bend back to provide correct chainline). You need (included) spacer to fit it on BB30 frame.

With Right arm of BB30 version on BB86 frame, there will be a problem with chain line.
That BB30 right side sit flush on bb that is 68mm wide without spacer. Now you are using 86.5mm wide BB. which means your right side spider will be pushed out by at least 9mm (without any spacer to remove to bring it back to the frame). Longer spindle or alternative spindle can't help this chainline issue.
Tell me if you think this is fine.

by Weenie


Jian81
Posts: 36
Joined: Mon Jun 15, 2015 1:29 pm

by Jian81

Oh i get it now. Thank you so much for the detailed explanation. Makes perfect sense. Cheers!

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