What Is A Freehub? (And Freehub Standards Explained)

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reviewed by Rory McAllister

The bicycle freehub is the mechanism that allows the rear wheel to turn freely when the pedals are not being engaged.

Located in the hub of the rear wheel, the freehub is what allows you to “coast” on a bike, meaning the wheels can keep turning while the pedals remain still.

The freehub is integral to the design of modern bicycles and has largely replaced older “freewheel” systems that were commonplace on older bikes.

As an experienced bike mechanic, I’ve seen plenty of cyclists run into mistakes and misunderstandings when it comes to freehubs – often with costly consequences when it comes to compatibility issues.

In this guide, we’ll walk you through the essential knowledge all cyclists should understand about freehubs, including how they work, how they differ from “freewheels”, and the different freehub compatibility standards used by different manufacturers.

We’ll be covering:

  • What Is A Freehub On A Bike?
  • How Does A Freehub Work?
  • Freehub Vs Freewheel: What’s The Difference?
  • 6 Key Freehub Standards To Know
  • Can Freehub Bodies Be Swapped Out Of Wheels?
What Is A Freehub? (Title Image)

What Is A Freehub on a Bike?

The freehub extends out of the right-hand side (the “drive-side”) of the rear wheel’s hub.

It is encased in a “freehub body”, which has splines that the cassette slides onto, allowing the freehub to act as the interface between the rear wheel and the bike’s drivetrain.

The key function of the freehub is to allow the rear wheel to disengage from the drivetrain while the pedals aren’t turning, allowing the bike to continue to move forward while the cyclist isn’t pedaling.

Without a freehub, you would have to keep pedaling the whole time that the wheels are turning, including when riding downhill. Bikes without freehubs are known as fixed-wheel or “fixie” bikes.

A bike freehub sits on a blue cloth surface.

How Does A Freehub Work?

The design of a freehub is surprisingly simple.

The freehub consists of a cylindrical chamber with a ratchet system inside. When you apply power through the drivetrain, the ratchets engage, gripping the hub and enabling the transfer of power to the wheel.

When you stop applying power, the ratchets disengage, enabling the wheel to continue spinning even though the pedals are not.

There are two main ratchet systems used in most freehub designs.

Animated diagram showing how a pawl-based freehub mechanism works.
The red arrows indicate which way force is being applied to the ratchet gear (green). The gear only moves when force is applied counterclockwise. The pawl (pink) prevents the gear from rotating clockwise.
Credit: Arglin KamplingCC BY-SA 4.0, via Wikimedia Commons.

The first is the pawl system, in which spring-loaded pawls catch onto teeth when you apply power to the freehub via the chain (demonstrated in the diagram above).

The second system features interconnecting rings with teeth on each side. When power is applied, the interconnecting rings come together and interlock to create engagement in the freehub. 

Freehubs using either system can also have a varied number of engagement points. This is how many times the freehub is capable of engaging through a full 360 rotation.

The more points of engagement, the more instantaneously and smoothly the freehub will engage when you start pedaling. Fewer engagement points can create some give when you start to pedal, with a slight knocking feeling in the pedals as the freehub engages.

A freehub with, say, 18 points of engagement (relatively few for a freehub) will make a more distinct clicking noise while coasting.

A freehub with a high number of points of engagement, 54 for example, will have more of a high-pitched whine when coasting due to the higher frequency of the noise of the freehub clicking past its engagement points.

Freehub Vs Freewheel: What’s The Difference?

Close-up of a freewheel on a vintage bike.
Close-up of a freewheel on a vintage bike.

Freehubs and freewheels both perform the same function but work very differently.

A freehub is a ratchet system that sits inside the wheel’s hub. The cassette has no moving parts; it is simply a collection of sprockets that slot onto the freehub body and is secured with a lockring.

Although the terms are often (wrongly) used interchangeably, freewheel systems do not use a cassette.

Unlike a freehub, the freewheel mechanism is separate from the rear wheel’s hub. The freewheel is integrated with a cluster of gear sprockets (resembling a cassette) as a single unit, which is screwed onto threads on the wheel’s hub.

Freewheels are a much older design but have largely been rendered obsolete on modern bicycles by freehubs.

Freewheels were difficult to remove, more prone to reliability issues, and were limited to fewer “speeds” (the number of gears) than freehub systems.

Typically, freewheels are found on bikes with 5 to 7 speeds built up until the late 1980s, whereas freehubs are found on most bikes with 7 or more speeds built after that point.

A bike mechanic slots a cassette onto a freehub body.

6 Key Freehub Standards To Know

With freehubs, there are numerous types to be aware of, known as “freehub standards”. Different cassettes and hubs are compatible only with a certain freehub standard, as their freehub bodies have different shapes or spline patterns.

As groupset technology has evolved to have ever-increasing numbers of speeds, freehub designs have had to evolve to accommodate the extra cassette sprockets, which is partly why there are so many varying designs.

Here are six of the most common freehub standards used on modern bikes: 

Shimano/SRAM Hyperglide

The most common freehub standard is the Shimano/SRAM Hyperglide.

This consists of 9 splines on a circular piece, with one spline being smaller than all the others to ensure the cassette goes on with the correct orientation. 

There are two versions of this freehub standard. One was made for 8, 9, and 10-speed drivetrains, and the other is for 8, 9, 10, and 11-speed drivetrains.

The 11-speed-compatible freehub body is slightly longer, and spacers are required to use cassettes with fewer than 11 sprockets.

Shimano Micro Spline

The Shimano Micro Spline system was first released to be used with the Shimano XTR 9100 12-speed mountain bike groupset.

Over the past few years, this technology has trickled down to Shimano’s SLX and Deore XT groupsets.

The Micro Spline freehub is similar to the Hyperglide in the fact it uses small splines to seat the cassette. The big difference comes in the size and the amount of splines. 

It’s designed to work with 12-speed cassettes and has some excellent advantages compared to other freehub systems. You can go as low as a 10-tooth cog on the cassette, which is an advantage when using a 1x drivetrain.

It has better weather protection and improved gear stepping for silky-smooth shifting. 


The SRAM XD was designed to accommodate SRAM’s 11- and 12-speed mountain bike cassettes.

Other benefits include that SRAM XD freehubs can use cassettes with a 10-tooth cog and have an improved seal to avoid dirt and water getting to the bearings.

The XD has a very different spline configuration from the Hyperglide and the Micro Spline, with only a few small splines and a threaded fitment above. It’s simple but very effective as a freehub standard.


The SRAM XDR is very similar to the XD, but instead of being designed for mountain bikes, it’s designed for road bikes.

With road bike cassette spacing being slightly different, the XDR freehub body is 1.85 mm longer than the XD body.

The XDR comes with all the advantages of the XD, and a small spacer can be used on mountain bikes, making the XDR an XD-compatible freehub.

Campagnolo FW

Unlike SRAM and Shimano components which are often interchangeable, Campagnolo mechanisms are usually proprietary.

The Campagnolo FW freehub body is functionally similar to the Hyperglide but with larger splines in a different configuration.

The Campagnolo FW freehub can accommodate cassettes with 9 to 12 sprockets.

Campagnolo N3W

The N3W (“Next 3 Ways”) is the latest freehub standard design from Campagnolo.

It is very similar to the Campagnolo FW, but the N3W can cater to 13-speed drivetrains. It was built specifically for the 13-speed Campagnolo EKAR gravel groupset.

Surprisingly, the N3W is shorter than the FW and, with an adapter, can work with Campagnolo’s road bike cassettes.

The N3W enables a massive gearing range as it can work with cogs with as few as 9 teeth, allowing for extended gear ratios even when used with a 1x drivetrain.

Can Freehub Bodies Be Swapped Out Of Wheels?

The process of removing a freehub body from a wheel.

A potential problem for cyclists is investing in a set of wheels only to find the freehub body isn’t compatible with their bike’s drivetrain.

An example is a bike having a Shimano drivetrain, but the wheels having a Campagnolo FW freehub body.

It is often possible to replace a freehub body with a different standard. You will find that with many wheelsets, you can buy freehubs that can be interchanged to suit the groupset you’re using.

However, there are other considerations and compatibility issues to be aware of. Here’s what you need to know:

Matching Hub Designs

The new freehub to be fitted has to match the hub design.

When ordering a replacement freehub body, you can often find a complete list of compatible wheelsets by crawling through the product specifications.

If the new freehub body doesn’t match the wheel’s hub, then you are not going to be able to make it work, no matter how hard you try.


You will also need to pay close attention to the speeds too. There’s no point fitting a 10-speed freehub if you have an 11-speed cassette. Unfortunately, it just won’t work.

If you have an 11-speed-compatible hub and a 10-speed cassette, you can use spacers to make it work, however.


Replacing a freehub body can require some specialist tools, and if you go into the process without them, you can end up damaging the wheels.

We highly recommend investing in the correct tools or heading to your local bike mechanic to do it for you.

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Robbie has traveled the globe as an endurance athlete and bikepacker, breaking world records and competing in international ultra-cycling events such as the BikingMan series and the Transcontinental Race. He's also worked as an ambassador for some of the industry's leading names, including Shimano and Ritchey. If Robbie's not on a bike, he's either fixing them or out walking with his dog!

2 thoughts on “What Is A Freehub? (And Freehub Standards Explained)”

  1. Excellent article! I’m about to purchase a new, wider-range cassette and wanted to be sure it would fit my freehub. Given the information presented here I found it will (and learned of other freehub standards I was unaware of). Thanks!


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