Let’s talk things Thru: the Tailfin Guide to wheel axles

Axle (noun) : a rod or spindle (either fixed or rotating) passing through the centre of a wheel.

At heart, wheel axles are a very simple concept. But that hasn’t stopped the cycling industry doing it’s best to make the subject as complicated as possible. The purpose of this article is to explain as simply and clearly as possible the different types of wheel axle.

Why do you need to know any of this? In a nutshell, it’s because Tailfin racks work by replacing the axle of your rear wheel with a specially designed axle of our own. If you want to use a Tailfin rack, you need to know the correct Tailfin axle to order along with it.

There are two different types of wheel axle out there. By far the most common is the one on the left side of this picture, called a Quick-Release axle (or a QR, or QR skewer). The QR skewer was invented in 1927 by Tullio Campagnolo, and it’s design has stayed pretty much the same ever since then.

The axle pictured on the right is called a thru axle. This is where things start to get a little more complicated. While pretty much all QR skewers are interchangeable with each other, there are many different types of thru axle.

So how do you tell a QR from a thru axle? The simplest way to do so is by looking at the axle itself. A QR is just 5mm in diameter, while thru-axles are much thicker.

You can also tell what axle you need by looking at your bike frame. On a QR compatible frame, you mount the wheels by slotting the wheel between two U-shaped mounts called ‘drop-outs’.

On a thru axle compatible frame, the ‘drop-outs’ are not U-shaped at all, but a closed loop. You fit the thru axle by pushing it through the round holes and threading it into one side of the drop outs.

If you’ve had a look at your axle or frame and can see that you need QR skewer for your Tailfin rack, then you can stop reading now. Simply select the QR option at the checkout and you’re good to go. If it looks like you need a thru axle for your Tailfin rack, there’s one last thing to check.

Because thru axles are a relatively new development invention, there is currently no industry standard. Countless different manufacturers produce their thru-axles to different specifications, making it impossible for Tailfin to make a single thru axle that will suit every bike.

What we have done is produce a set of adapter collars that will come with your thru axle that will make it compatible with your bike – all you need to do is check what ‘pitch’ you require.

Pitch refers to the thread on one end of a thru axle –  it describes the distance between each groove of the thread, or how ‘coarse’ or ‘fine’ that thread is. There are three different pitch measurements used in thru axles – 1.00mm, 1.5mm and 1.75mm. You can check what pitch measurement you need to use by checking the table here. Once you’ve matched your bike to it’s manufacturer, simply select the correct pitch at checkout.