In the world of bicycles, Shimano and Sram are almost the dominant players in the freehub and cassette market. With technology advancing rapidly, the compatibility between components has become increasingly complex. We’ve put together a simple guide to help you understand the historical changes and current options. If you are using a Campagnolo cassette, remember, it can only be paired with a Campagnolo freehub; Shimano or Sram freehubs won’t work.

If you want to know whether the cassette or freehub you have can be paired together, just skip to the table at the end.

Shimano

Shimano's Hyperglide (HG) freehub was released in the 1980s, featuring 9 splines with a larger central slot to ensure proper gear alignment during shifting. There are several versions of the HG freehub.  

Shimano HG "8-11" Speed Mountain Freehub

When the 9-speed was introduced, the chain became narrower, and the gear spacing was smaller than the 8-speed, but the overall width remained the same, so no spacer was needed. When designing the 11-speed, Shimano anticipated this change, making the 10-speed spacing narrower than the 9-speed. The Shimano 10-speed cassette is narrower than the 9-speed, requiring a 1mm spacer. The 11-speed mountain cassette can be directly mounted onto a freehub from 8 to 10 speeds without a spacer, but road 11-speed requires removing an internal spline.

Shimano HG L2 12-Speed Road

In 2021, Shimano introduced the 12-speed Dura-Ace and Ultegra road groupsets, offering faster and smoother shifting. They brought the Hyperglide + technology from mountain bikes to the road. The 12-speed cassette is compatible with 11-speed road freehubs, but a 12-speed-specific freehub cannot be used with 11-speed components.

Shimano HG 10-Speed ONLY Freehub

For a period, Shimano released freehubs that were only compatible with 10-speed cassettes. No spacer was needed, but 11-speed or 12-speed cassettes would not fit, and other speeds might not be compatible either, as the splines on the 10-speed freehub are higher.

Shimano MicroSpline (MS) 11/12-Speed

As mountain cassettes evolved to 12-speed, Shimano introduced MicroSpline. The MS freehub is compact and lightweight, featuring 23 splines and using a lighter alloy to distribute forces more efficiently.

Sram

Shimano HG-Style
Sram's HG-style cassettes have a similar spacing to Shimano’s, but there is an exception with the 10-speed. Sram's 10-speed cassette is the same width as the 8/9-speed, while Shimano's 10-speed cassette is 1 mm narrower.

Compatibility and Spacer Table:

XD 11 & 12-Speed

Sram's XD driver allows the smallest cog to be as small as 10 teeth, improving the gear ratio. It is lighter and more durable than the HG freehub because the cassette does not wear down the splines.

XD-R 11 & 12-Speed

The road version of the XD-R is compatible with mountain cassettes, but requires a 1.85mm spacer. The road XDR cassette does not need a spacer. There are no compatibility issues between 11-speed and 12-speed Sram cassettes. The SRAM RED eTap AXS and Force eTap AXS road cassettes use the XDR freehub.

Sram XX1, XX1 Eagle, X01, X01 Eagle, X1, GX, and GX Eagle all use the XD freehub. The Sram NX 12-speed cassette, however, uses the Shimano HG freehub, so this is important to note. To check compatibility, look at the smallest cog. If it's 10T, it should use an XD-style freehub; if it's 11T, it may be a Shimano HG freehub.

Cassette Compatibility Table:

I hope this more vivid explanation helps you feel more confident and efficient when selecting and using bicycle components.