Most direct-drive smart trainers on the market are designed for road bikes with anywhere from 8 to 11 speed gear cassette on the wheel. With 12 speed drivetrains occupying the top of the bike industry, I thought I’d add this post on how to select cassettes.
Here is our guide to Direct Drive Trainers.
If you’ve purchased a trainer where the cassette is not included, we recommend you purchase a cassette that closely matches what’s on your bike’s rear wheel for the best shifting performance and compatibility with the rest of your drivetrain.
- The number of speeds should match what’s on your bike.
- The gear range should also match (“11-28” means the smallest cog has 11 teeth, and the largest cog has 28). You can count the teeth to be sure, or look for the number stamped on the cog.
- Ideally, the brand of the cassette should match the brand of your rear derailleur.
To install the cassette, please see our guide to Installing a Cassette.
Some bikes are equipped with a 12 speed cassette on the rear wheel. Most direct-drive trainers come with a freehub body compatible with 8 - 11 speed Shimano and SRAM road cassettes, so you may need to swap out the trainer’s stock freehub body before installing your cassette. Please check with your trainer’s manufacturer for additional info.
Campagnolo 11 and 12 speed cassettes will only fit on a Campagnolo-specific freehub body.
SRAM 12 speed road bike cassettes will only fit on a SRAM XDR freehub body
SRAM 12 speed “SX” and “NX” Eagle mountain bike cassettes will fit a standard Shimano/SRAM freehub body. These have an 11 tooth smallest cog.
Higher-end SRAM 12 speed mountain bike cassettes will fit either a [SRAM XD freehub body, or an XDR freehub body with an additional 1.8 mm spacer. These have a 10 tooth smallest cog.
Most trainer manufacturers make all three of these optional freehub body types to retrofit on their trainers.
Shimano introduced their 12 speed mountain bike drivetrains in 2019, and these cassettes fit a new Microspline freehub standard. At this time, we are not aware of trainer companies that have a Microspline retrofit, but we will update when this changes.