There are two requirements for a cassette to be compatible with a particular hub
- The splines of the hub should match the cutout on the cassette. If that condition is not met, there is no way to slide the cassette onto the hub.
- The cassette should be narrow enough to fit on the freehub body.
To ensure that one hub can accept a great number of cassettes of different speeds, the sprockets get thinner and closer to one another as the number of gears increases.
Shimano
MTB
Shimano’s 8, 9, 10, 11 and 12-speed MTB cassettes are close in width.
The table below contains the width of 8-12-speed cassettes:
| NUMBER OF SPEEDS | TOTAL WIDTH |
|---|---|
| 8 | 35.4mm |
| 9 | 36.5mm |
| 10 | 37.2mm |
| 11 | 40.6mm |
| 12 | 41.2mm |
Spline Difference
The width of the cassette is irrelevant when its cutout is incompatible with the splines of the hub. This would be the case for Shimano’s microspline 12-speed cassette.
The 12-speed cassettes from the Microspline family are compatible only with Microspline hubs. Those cassettes cannot be installed on a standard Shimano Hyperglide hub.
That said, 10-speed HyperGlide MTB hubs can accept 12-speed HyperGlide cassettes made by other companies such as SunRace.
Road Cassettes
Shimano’s 10-speed road cassettes are narrower than 8,9, 11 and 12-speed models. Consequently, the matching hubs are narrower too.
Or in other words, you will be unable to install a 12-speed cassette on a dedicated Shimano 10-speed road cassette due to the lack of space. Those cassettes accept only 10-speed road cassettes and nothing else.
However, an 11-speed hub can also run a 10-speed cassette with the help of spacers to make up for the extra width. Thus, some 10-speed road bikes actually use 11-speed hubs. Those hubs will allow the installation of a 12-speed cassette with matching splines upon removing the spacers.
SRAM
SRAM’s 12-speed NX and SX cassettes can be installed on standard 10-speed SRAM and Shimano hubs (the type of hubs compatible with the PowerGlide and HyperGlide cassettes).
However, SRAM’s GX cassette requires an XD driver. Therefore, it’s not possible to install a GX cassette on a standard Shimano or SRAM 10-speed hub. This conversion will require a hub with an XD driver.
Campagnolo
A 12-speed Campagnolo cassette can be installed on a 10-speed hub, but only when the hub is also made by Campagnolo.
Campagnolo cassettes are not compatible with Shimano and SRAM hubs.
The above can seem a bit complicated and I will therefore summarize it in a simple table:
| Manufacturer | Hub Type | Cassette Compatibility |
| Shimano + SRAM | MTB 10-speed | 8, 9, 10, 11 MTB 12-speed HyperGlide Models SRAM NX and SX 12-speed models |
| Shimano | 10-speed Road | only 10-speed road cassettes |
| Campagnolo | 10-speed | 9,10,11, 12-speed Campagnolo cassettes |
What is the advantage of a 12-speed cassette over a 10-speed model?
- Smoother transitions
The extra cogs on the cassette make the jumps between gears smaller. As a result, the rider can maintain a smooth cadence. Cadence is a term describing the rotations of the cranks per minute. High cadence (e.g., 90 RPM) is associated with higher average speeds and lower energy expenditure.
What are the downsides of installing a 12-speed cassette on a 10-speed hub?
The main downsides of this conversion are the extra expenses. A switch from 10 to 12 speeds will require the following parts:
- New hub (If the current isn’t compatible. The wheel will have to be rebuilt too.)
- New cassette (12-speed cassettes aren’t the cheapest.)
- 12-speed shifter + cable + housing
- New derailleur if the current one cannot cover the entire cassette
- New chain (12-speed chains are narrower to prevent rubbing against the cogs)
- New chainring (the narrow 12-speed chains will bind when used on standard 10-speed chainrings)
