What Is The Difference Between Quick Release And Thru Axle?

For years, connecting a wheel to a bike was a simple process that used quick release skewers to connect your wheels. Today, there are options and attaching a wheel to a bike can be confusing and somewhat of a puzzle to figure out.

Along with different attachment types, hub spacing, or how wide your hub is, is different for different attachment types, further complicating things. This article walks you through the attachment types and discusses the associated hub spacing for each option. Let’s get to it.

Anatomy Of A Hub

Let’s start with the anatomy of a hub so we are all on the same page with the names of the parts.


Full Front Hub

Hub End Caps

Quick Release, 12mm, & 15mm End Caps

Bearing (Silver & Blue Part)

Axle (Threaded Part)

Hub Shell (Part With FLO That Holds The Bearings, Axle, & End Caps)

Rear Hub (Adds A Freehub, The Red Part)

Axle Types

There are two primary axle types for hubs. The first is known as "Quick Release" (QR) and the second is known as "Thru Axle." Both are explained below.

Quick Release Axle Design

The quick release option uses compression to hold the wheel in place. With something known as a quick release skewer. The skewer has a small diameter and passes through the center of the axle. You can see an axle that accepts a quick release skewer below.

Thru Axle Design

A thru-axle uses a much larger diameter rod that is threaded into the frame to hold the wheel in place. There are two primary sizes which are 12mm and 15mm. You can see an axle that accepts thru-axles below.

Attachment Options

As discussed above there are different attachment options. Below we show a quick release skewer, a 12mm thru-axle, and a 15mm thru-axle. It should be noted that generally in road and gravel cycling, 15mm thru-axles are often only seen on front wheels and rear wheels are generally 12mm. You can also see from the pictures below that some of the skewers and thru axles have levers to tighten the attachment. Others do not and must be tightened with a tool. You can find both options for quick release and thru axles.

Quick Release Skewer

12mm Thru Axle

15mm Thru Axle

End Cap Options

The end caps for hub must accommodate the attachment type. The end cap for a quick release, 12mm thru axle, and 15mm thru axle are all different. Please are pictures with the attachment type and its corresponding end caps installed.

Quick Release Skewer & Quick Release End Cap

12mm Thru Axle & 12mm End Cap

15mm Thru Axle & 15mm End Cap

Attaching To The Bike

The images below show the full hub assemblies which include, the hub shell, bearings, axle, end caps, and corresponding skewer. For the quick release skewer compression is used to hold the hub to the frame. For the thru axle designs, they are threaded into the frame.

Full Quick Release Hub Assembly

Compression Is Used To Hold The Hub To The Frame

Full 15mm Hub Assembly

Threaded Insert Of The Frame To Hold The Hub In Place

Hub Spacing

Each end cap option changes the width of the hub, which complicates things the most. Your frame will be the determining factor of the hub spacing you need. Here is the spacing for each attachment and end cap option.

Quick Release

  • Front Hub: 100mm
  • Rear Hub: 130mm


12mm Thru Axle

  • Front Hub: 100mm
  • Rear Hub: 142mm


15mm Thru Axle

  • Front Hub: 110mm
  • Rear Hub: N/A

The Bike

A bike comes designed for one of the attachment styles. Unfortunately, you cannot switch between the different types. Generally bikes use a semi consistent sizing per discipline but that isn’t always the case. Here is a general rule of thumb.

Road Bike w/ Rim Brakes

  • Quick release skewers.


Road Bike w/ Disc Brakes

  • 12mm thru-axle
  • Older bikes may be quick release.


Gravel Bike w/ Disc Brakes

  • 12mm or 15mm thru-axle for the front wheel and 12mm thru-axle for the rear wheel.

Hub Design

We’ve done our best to design hubs that can be updated to match the bike. For example, since disc brakes can have many different options our hubs allow for the end caps to be interchanged making the wheel fit multiple bike styles.

Final Thoughts

Your bike is ultimately the deciding factor for the wheel attachment type. We hope this article has helped you understand how to identify the differences. Next we will discuss the pros and cons of thru axles vs quick release skewers.



I believe you will find the article below helpful.


Take care,


Jon Thornham November 18, 2020

Great article, but what I have wondered about thru axles, and you don’t address this at all, is why? It is likely that thru axles are stronger, but why do we need them on road or even gravel bikes? Properly installed and tightened quick release axles have been ridden in some incredibly rough conditions. I have seen axles fail, but the skewers held. Beefier axles with QR skewers would have been all that was needed in those situations. I understand that disc brakes likely generate different forces than rim brakes. If so, please explain. In your blog on this page – https://flocycling.com/blogs/blog/rim-brake-vs-disc-brake-whats-the-difference you say that disc brake equipped wheels are easier to change. Not if they are used in conjunction with a thru axle. You also state that disc brakes allow for wider rims and tires. On road and gravel bikes, the brakes are rarely the limiting factor. The frame and/or fork is. On mountain bikes, cantilever, U brake and V brakes can be set up to accommodate most any rim/tire width. And, yes, rim brakes do generate more wear on the rims, and improve braking under extreme wet conditions. Disc brakes generate more stress on spokes, and for this reason, many tandem builders discourage their use. Constant light application of rim brakes on long descents can generate excess heat, which can damage the rim and or blow out the tire, but applying the brakes correctly and alternating between front and rear can alleviate this issue.

If disc brakes and thru axles don’t define solutions looking for problems, they come darn close.

Gary Kuchel November 18, 2020

Thanks Ted! I updated this.

Take care,


Jon Thornham September 28, 2020

The the Axle Design section, you repeat the “Quick Release Axle Design” subheader for both the quick release and thru axle sections.

Otherwise, great article!

Ted Boone September 28, 2020

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