So, you've managed to choose the right wheels for you, successfully select the correct freehub option for your cassette and order some of our sweet wheels - thank you! After checkout on our website, we will email you a confirmation and ask you to complete a form telling us what the axle requirements are for your frame and fork. This will help us choose the correct axle adapters for your wheels. This article is designed to help you choose the correct options, so you can get up and rolling as soon as possible after receiving your wheels!

Note: If your bike is using rim brakes, you don’t need to think about this - 99.9% of all rim brake bikes and wheels use the same fittings. We’ll send your wheels with the parts you need to fit them to your bike.

Thru-Axle VS Quick Release

Wheels are held in the dropouts of a frame or fork using either a Thru-Axle or Quick Release (QR) skewer. You can tell if your frame and fork are designed for quick release or a thru-axle by looking at how the wheels are attached. A thru-axle holds the wheel in a closed (or O-shaped) dropout, whilst a QR skewer holds a wheel in an open (or U-shaped) dropout.

Thru-Axles and Closed Dropouts

To remove a thru-axle wheel from your frame or fork you need to unscrew the whole thru-axle and remove it before the wheel can be taken off the bike. Thru-axle type frame dropouts are closed and the wheels cannot drop out of them until the thru-axle has been removed - this is one of the reasons why thru-axles are very common on mountain bikes. Wheel positioning in the frame is much more reliable than with a QR system, meaning that thru-axles work well for disc brakes - as a result, you’ll find them on the majority of disc-brake bikes, no matter the discipline. 

The axles are usually provided with frames and forks and can be brand-specific. We’ll set up your wheels to fit your bike using your existing axles. If none were supplied with your frame or fork, please get in touch and we can help to find some compatible ones.

Note: Thru-axles may have a lever at one end (similar to a QR skewer), to allow tool-free removal and installation. Alternatively, they may have an Allen/hex bolt at one end, which means that you'll need an Allen/hex key to remove and install your wheels.

QR Skewers and Open Dropouts

A QR wheel can be removed from the frame or fork without removing any parts. Once the cam-operated lever on the end of the QR skewer has been loosened, the wheel can be removed. If you are using open dropouts, you can select the QR option when we get in touch. 

If your bike uses rim brakes, it's more than likely that you have open dropouts and will require QR skewers and axle adapters. As above, if you're ordering rim brake wheels, you don't need to worry about a thing!

Thru-Axle Sizes

There are a number of different thru-axle sizes that frames and forks are supplied with. There are a few common thru-axle sizes, and some less common. We won’t go into the details of how and why they came about here, as it's a bit of a complicated area of the bike industry! However, there are two important things for us to know to get your wheels setup correctly:

  • The diameter of the axle or dropouts in the frame and fork
  • The distance between the dropouts

A lot of brands publish these axle sizes on their websites for their bikes, frames and forks. Usually, this is found under the full/technical specifications section, in the frame/fork/front/rear hub information sub-sections. However, sometimes this information can be hard to find online. In that case, it can be useful to measure your fork and frame directly.

You can measure the diameter of the circular dropouts on your frame and fork using a calliper, tape measure or ruler. On the front fork this will be approximately 9mm, 12mm (common for road and gravel), 15mm (common for MTBs) or 20mm. On the back of the frame this will be approximately 10mm or 12mm (very common).

Measure the distance between the inside face of the frame and fork dropouts using a tape measure or ruler. On the fork this will measure approximately 100mm (common for road and gravel) or 110mm (common for MTBs). On the frame this will measure approximately 130mm, 135mm, 142mm (common for road and gravel), 148mm (common for MTBs), 150mm or 157mm.

Front Thru-Axle Size (Diameter x Width)

Used on

9 x 100mm*


12 x 100mm

Road, Gravel

12 x 110mm (Road Boost)*Road

15 x 100mm (non-Boost)

Mountain, Gravel, Road

15 x 110mm (Boost)


20 x 100mm (non-Boost)*


20 x 110mm (Boost)*


Rear Thru-Axle Size (Diameter x Width) 

Used On

10 x 135mm

Road, Gravel

12 x 130mm*

Specialized SCS bikes only

12 x 135mm

Road, Gravel

12 x 142mm (non-Boost)

Road, Gravel, Mountain

12 x 148mm (Boost and Road Boost)

Mountain, Gravel, Road

12 x 150mm


12 x 157mm*


12 x 157mm (Super Boost)*


* Send us an email with your bike details if you’ve measured your frame and it’s one of these, we’ll be able to help find the right wheels to fit your bike.

Quick Release Sizes

The majority of open-dropout, QR-type frames, forks and skewers are the same size. That is:

  • A fork dropout of approximately 100mm width
  • A frame dropout of approximately 130mm width (rim brake) or 135mm width (disc brake)
  • A skewer of approximately 5mm diameter

However, some mountain bikes use what is known as 'Boost QR'. This uses a wider spacing on the fork dropout (110mm) and frame dropout (141mm).

What's next?

Once you have filled out the form with your axle requirements, we will set your wheels up with the right axle adapters to fit your frame and fork before shipping. If you already have a pair of our wheels and would like to use them on a different bike or are changing your forks, you can purchase replacement axle adapters if needed on our site. Our Knowledge Base contains lots of useful information to guide you through the process of changing your front and rear adapters.

We do understand that this can be a confusing area however - we struggle with it from time to time too! If it's still unclear, you can select 'Unsure' on the form, letting us know your frame/fork make, model and year of manufacture and we will do our best to determine the correct axle requirements for you. However, if you do have the details available, it will speed up the dispatch process. 

If you have any questions, please let us know. You can speak to us on live chat, over the phone, or email us and we’ll respond within 24 hours.