Freehub and freehub body: function, compatibility and conversion

In front of you the trail, behind you a cloud of dust – and in between, a soundtrack of tyre noise, birdsong and the hum of your hub. Or more precisely: the freehub on your bike. When you pedal, the freehub body transfers the power from the sprocket to the hub. When you stop pedalling, it allows you to roll effortlessly. Some riders even appreciate it for its distinctive sound – like a catchy tune.

Here we give you an overview of which freehub body is compatible with which drivetrain and explain how the freehub on your bike works. This is helpful when choosing a new cassette, rear hub or wheelset, or when replacing the freehub body during a drivetrain upgrade.

Converting the freehub body: best done tool-free

How exactly the freehub body is replaced varies from one hub manufacturer to another. Many manufacturers such as Hope, DT Swiss, SRAM or Shimano allow tool-free replacement: the freehub body is simply pushed on. Whether this is also the case for your hub or how the replacement works instead can be found in the user manual or by contacting our service team.

You will need some tools beforehand to remove the wheel and take off the cassette. You can find out how this works in our dedicated guides: How To: change an MTB cassette / How To: change a road bike cassette

Overview: the most common mounting standards

To help you keep track when shopping, we have briefly summarised the most common mounting standards and cassette compatibilities. If you are looking for a quick overview, you will find it further below.

What fits Shimano HG (MTB / road)?

Shimano Hyperglide (HG) has long been the most widely used standard. As of January 2026, there are three variants:

• Shimano MTB is suitable for 8-, 9-, 10- and 11-speed mountain bike cassettes from Shimano, where the smallest sprocket has at least 11 teeth. Various other manufacturers also offer cassettes for the classic HG standard, in some cases even up to 12-speed (including SRAM, except XD/XDR). The cassette interface is 34.9 mm long and has nine splines. Shimano also refers to this standard as “HG spline M”.
  Note: Shimano 8-, 9- and 10-speed road cassettes also fit.
• Shimano Road is suitable for 8-, 9-, 10-, 11- and 12-speed road cassettes from Shimano and various other manufacturers, where the smallest sprocket has at least 11 teeth (including SRAM, except XD/XDR). The cassette interface is 36.75 mm long and has nine splines. You can mount 8- to 10-speed cassettes using a spacer. Shimano refers to this as “HG spline L”.
  Note: The 11-speed road cassettes CS-HG800 and CS-HG700 also require a spacer.
• Shimano Road 12-speed: Shimano’s Dura-Ace rear hubs feature a specific freehub that is supplied in combination with Dura-Ace wheelsets. The 12-speed cassette engages with 18 splines that are 37.65 mm long. Shimano calls this freehub “HG spline L2”.
  Note: This freehub is only compatible with 12-speed cassettes.

Note: HG freehub bodies are not compatible with SRAM XD/XDR or Campagnolo cassettes.

What is the difference between SRAM XD and XDR?

The XD standard was introduced by SRAM to enable the use of cassettes with a smallest sprocket of 10 teeth or less (e.g. e*thirteen with a 9-tooth sprocket). It is compatible with 11- and 12-speed cassettes from SRAM and various third-party manufacturers.

SRAM XDR is an adaptation of this standard for road bikes and features a freehub body that is 1.85 millimetres longer. It is compatible with 12- and 13-speed cassettes from SRAM road and gravel groups. When using a 1.85 mm spacer, it is also compatible with SRAM XD cassettes.

Note: not compatible with Campagnolo or Shimano (HG) cassettes.

Special cases: singlespeed and fixie

For singlespeed and trial bikes, there are special hubs with narrow freehub bodies designed to mount a single sprocket and usually offering enough space to adjust the chainline with spacers. The narrow freehub allows wider hub flanges, enabling the construction of more symmetrical and stable wheelsets. However, converting such hubs to a geared drivetrain with a cassette is not possible. On the other hand, you can convert Shimano road, MTB and SRAM freehub bodies to singlespeed use with appropriate spacers and singlespeed sprockets. Some singlespeed sprockets feature a wider interface to protect the freehub body.

Another option is singlespeed hubs with a threaded interface. This design requires a sprocket with an integrated freewheel, i.e. a freewheel sprocket.

Track bikes and fixies do not have a freehub at all. Here, the sprocket is screwed directly onto the hub body or mounted via an adapter and secured with a lockring. When the rear wheel rotates, the sprocket and crank rotate as well.

Engagement points and noise level

The finer the engagement of the pawls or ratchet teeth, the more engagement points are available per hub revolution. This reduces the engagement or pickup angle when pedalling. In other words: the crank’s free movement decreases and after coasting you regain drive almost immediately. This is especially important for trial, mountain and gravel riders. On road or triathlon bikes, where you aim for a constant cadence anyway, this is less critical. Here, fewer but larger pawls can offer greater robustness and resistance to pedalling forces.

The engagement system is also responsible for the sound you hear when coasting. The more engagement points your hub has, the higher-pitched the buzzing sound becomes. How defined and loud your freehub sounds depends on details such as how the manufacturer designs the ratchet rings or pawls – and on lubrication. The cassette, rims and even the frame can further amplify the sound as resonance bodies. This gives every bike its own unique road or trail soundtrack.

Materials: aluminium, steel, titanium

Freehub bodies are typically made from one of three materials, each with its own advantages and disadvantages:

• Aluminium freehubs are very common. They are lightweight, but when used with cassettes made of individual sprockets, pedalling forces can cause notches to form. That’s why many cassettes mount most sprockets on a carrier that spans the full width of the freehub.
• Steel freehub bodies are more robust and affordable, but heavier.
• Some high-end hubs feature freehub bodies made of titanium. This premium lightweight metal combines low weight with high durability.

Table: which freehub fits?

FAQ: freehub and freehub body

Which two checks determine compatibility?

A freehub body must 1. be compatible with the cassette you want to mount on it and 2. fit your hub. You can check 1. using the table above, and 2. depends on what your hub manufacturer offers.

Is replacement tool-free?

Many freehub bodies can be replaced without tools, as they are simply pushed on. It’s best to check the documentation from your hub (or wheel) manufacturer to confirm whether this applies or if tools are required. In any case, the cassette must be removed beforehand, which does require tools.

Does an 11-speed road cassette fit on HG Road?

Yes, Shimano 11-speed road cassettes fit on the HG Road freehub body (HG spline L). Some models (CS-HG800 and CS-HG700) require a 1.85 mm spacer. Note: some 11-speed road cassettes from other manufacturers are not HG-compatible.

Do I need Micro Spline for Shimano 12-speed MTB?

Yes, currently (as of January 2026), Shimano 12-speed MTB cassettes are only available for Micro Spline freehubs.

XD vs. XDR: can I run my XD cassette on XDR?

Yes, 11- and 12-speed XD cassettes can be mounted on XDR freehubs using a 1.85 mm spacer.

Campagnolo N3W – what’s different?

N3W freehub bodies are shorter than classic Campagnolo freehubs to allow space for smaller sprockets. With an adapter, you can also mount older Campagnolo cassettes.

Singlespeed/fixed: is there a freehub?

Singlespeed: yes. Fixed: no. Singlespeed means one sprocket with a freehub (either a threaded freewheel sprocket or a single sprocket with spacers on a freehub body). Fixed refers to a rigid drivetrain where the sprocket is fixed directly to the rear hub (usually threaded).

What causes the loud buzzing sound from my hub?

The noise comes from the freehub mechanism. Teeth that lock together in one direction slip over each other in the other direction, creating the sound. Engagement, lubrication, design and even other bike components all influence the sound and its volume.