Power Meter Crankset Bottom Brackets

Your bike’s bottom bracket is the bearing pair that your crankset’s axle rides on. And there are a lot of combinations, unfortunately. A LOT. We’ll break this into the three important questions which should help you determine what bottom bracket you need for your new power meter crankset.

1. What Size is Your Axle?

This will be the easier of the two main parts since we need diameter of where the axle rides on the bearings. In most cases, this is just one number. For example, Shimano uses 24 mm for both bearings, SRAM’s DUB uses 29 mm for both and ROTOR uses either 24 mm or 30 mm for both.

However, this can also be two numbers where each bearing is a different size. For example, SRAM’s GXP uses 24mm for the driveside bearing and 22 mm for the non-driveside. Also, Praxis’ M30 uses 30 mm for the driveside bearing and 28 mm for the non-diveside.

The Industry is now generally using a name for these designations so you will likely not have to know the exact dimensions of your axle: BB30, PF30, DUB, GXP, M30, Hollowtech, Ultratorque.

2. What Size is Your Bottom Bracket Shell?

This is the “character builder”. Bottom bracket shells can be threaded or smooth and have two dimensions. What is the shell width (see below) and what is the diameter of the hole where the bottom bracket bearing or bearing cup will fit.

Our last count is that there were 21 different categories, some of which had sub-categories. You’re reading this on a site that sells a lot of power meters, so we’ll assume you don’t want one of the myriad options that came before about 1990. We’ll leave those for another day. You’re welcome.

You will see names for these combinations that will make things a touch easier: BBRight, BSA, BB90, BB386, OSBB, T47, Italian, and so on.

The absolute best place to find this information is your frame manufacturer’s website. The information should be listed in the frameset composition and description.

3)  What Bottom Bracket Material Do You Want?

Finally resides bottom bracket bearing material. You now have two general choices: steel or ceramic. One is inexpensive, the other is very much not. However, the ceramic bearings themselves are rounder, roll more smoothly and are made to last longer.

Easy right? Of course, if you have any questions, just let us know. We’re happy to help!