SRAM Crank Arm Bolt

Here's another public service announcement.

I was servicing the bottom bracket on my MTB which is SRAM equipped. It has the X01/XX1/GXP style where a single bolt goes through the left crank arm and holds the entire bottom bracket together. This bolt torques to around 35-40 ft.lbs. When reassembling it, the head of the bolt sheared off at about half that torque. It turns out these bolts are made of aluminum alloy despite being a high torque, high stress application. Apparently SRAM uses steel bolts in the cheaper gruppos but tries to save a few grams (at the expense of durability) in their top of the line stuff. "Race to the lightest, at any cost". So, consider the alloy bolt a "consumable" and replace it even if it looks fine. Reading about this, I found that SRAM is now making a steel replacement bolt. They're still using alloy as the standard part but you can order the steel if you know the part number: 11.6118.066.000.

Yeah I'm not the only one to discover this: