Condensed Answer: A 12-speed cassette can be installed on a 142mm hub when the freehub body and the cassette are compatible.
If the freehub has HyperGlide/PowerGlide splines, the options are:
а. SRAM NX and SX cassettes
b. 12-speed HyperGlide models made by SunRace (or other brands).
If the hub has a Microspline freehub body, then 12-speed cassettes made by Shimano are the only option.
If the freehub body is SRAM’s XD, you will need a matching 12-speed cassette.
Hub Length and Cassette Compatibility
The 142mm measurement indicates the spacing/length of the hub and has no direct influence on the cassettes that the hub is compatible with.
However, the hub’s spacing directly influences the frame that the hub can be installed on. For example, if the frame’s O.L.D. is 135mm, then it won’t accept a 142mm hub.
The term over-locknut dimension or O.L.D. indicates the distance from one locknut of the hub to the other.
The freehub body is the element of the hub on which the cassette slides. It contains the ratcheting mechanism that allows the bike to coast. (That mechanism is responsible for the popular buzz sound that rear hubs make.)
It’s also important to know that freehub bodies have splines acting as anchor points for the cassette. The cassette should be machined for the splines of the hub on which it is installed. Otherwise, you won’t be able to slide the cassette onto the hub.
Consequently, the freehub body type and its width determine whether a hub is compatible with a specific cassette or not.
In the case of 12-speed cassettes, we observe the following dependencies:
- From 8 to 11 speeds, Shimano hubs fall under the category HyperGlide (SRAM’s equivalent is called PowerGlide). 12-speed Shimano hubs are part of the Microspline family and have different splines.
A HyperGlide hub can accept a 12-speed cassette under the following circumstances:
- The hub is made for at least 8-speeds (otherwise the hub is too short).
- The cassette is made for the HyperGlide family. SRAM’s NX and SX cassettes meet those criteria. It’s also possible to get a 12-speed HyperGlide cassette from SunRace.
If the hub is part of the Microspline family, a Shimano 12-speed cassette will be needed.
If the hub is SRAM XD, it can only work with a 12-speed cassette made for an XD hub.
What Are The Advantages of 12-speed Cassettes?
- Smooth Transitions
The main motivation to increase the number of speeds on a cassette is to make the transitions between gears as smooth as possible.
A 12-speed cassette offers small jumps which in return allow the rider to maintain optimal cadence even when shifting frequently.
The term cadence refers to the number of crank rotations per minute. A higher cadence such as 90RPM is considered a good combination of efficiency and decent power output.
- Better for 1x Drivetrains
12-speed cassettes offer a decent number of gears and a massive large cog (first gear). This makes them a decent choice for 1x speed drivetrains (single chainring).
The 12 gears diminish the main downside of a 1x drivetrain, namely the limited number of gear combinations.
What Are The Downsides of Switching to a 12-speed Cassette?
- Extra Cost
12-speed components are more expensive and thus absent from budget projects.
A 12-speed system has low tolerances. Or in other words, it takes more effort to maintain it because the gears are very close to one another. Properly indexing the gears and making final adjustments could be annoying.