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Bottom Brackets for Power Meter Cranksets

Your bike’s bottom bracket is a crucial part of your drivetrain. A bottom bracket is a set of bearings that your crankset spindle rotates on. While there are many commonly used bottom brackets, there is no industry standard which means there are many combinations and options. Here, we’ll break down finding a bottom bracket for your power meter crankset into the three questions which should help you determine what bottom bracket you need.

1. What Size is Your Axle?

This is often the easiest of the questions to determine. In order to determine what bottom bracket you need, we will need to know the diameter of your spindle. In most cases, the spindle is the same diameter across its entire length. For example, Shimano uses 24 mm spindles, SRAM’s DUB uses a 29 mm spindle and ROTOR has options for both 24 mm or 30 mm spindles.

However, some spindles are tapered and have a different diameter at one end than the other. For example, SRAM’s GXP uses 24mm at the driveside and 22 mm at the non-driveside. Praxis’ M30 uses 30 mm at the driveside and 28 mm at the non-diveside.

This information can often be found on a manufacturers’ website or can be physically measured with the crankset removed from your bike.

2. What Size is Your Bottom Bracket Shell?

This can be the trickiest of the questions to answer, but we hope to provide an easy way to find the answer. Bottom bracket shells can be threaded for threaded bottom brackets or smooth for pressfit bottom brackets. Once you’ve determined if your bottom bracket shell accepts a threaded or pressfit bottom bracket, we need two measurements to determine which bottom bracket will fit your frame. We need both the width and diameter of your bottom bracket shell.

With these two measurements and spindle diameter, you’ll now be able to find a compatible bottom bracket. Unfortunately, like we mentioned earlier, there are many bottom bracket options and nomenclature is not always the most clear. Our last count is that there were 21 different categories, some of which had sub-categories. Some bottom brackets like BB86 are easy. If you’ve got a 86.5 mm wide road shell or 91.5 mm wide MTB shell and a 41 mm shell diameter, this is the bottom bracket for you. Some can be more difficult to determine the name based purely on size. 

This is why we recommend checking your frame manufacturer’s website. It is the absolute best place to confirm the correct bottom bracket for your frame. This information is often listed under the specifications of your bike. You will see specific bottom bracket names like BSA, BB90, BB386, T47 and so on. This gives you the bottom bracket you need instead of having to measure your shell width and diameter. From here, you just need the bottom bracket that will match your spindle size.

Bottom Bracket Shell

3)  What Bottom Bracket Material Do You Want?

The final question with bottom brackets is if you want steel or ceramic bearings. Steel bearings are often more affordable while ceramic will provide less rolling resistance but are more expensive. Steel bottom brackets are a popular choice for many riders as they require less maintenance and because bottom brackets are a wear item, can be replaced more affordably. Ceramic bearings are designed for performance and reduce resistance within the drivetrain, are often machined at tighter tolerances and can use higher end greases and materials.

Of course, if you have any questions, just let us know. We’re happy to help you find the right power meter crankset bottom bracket for your bike!

Dave Harris

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