Some information about the Thru Axles / Through Axles

Let’s discuss some information about the Thru-Axle together. There may be some lacks in some aspects. If there is any wrong information, please correct the major bicycle enthusiasts.

Firstly, Thru-Axle (TA) is a large diameter threaded fastener that secures a bicycle’s wheel to the frame and fork, serving the same purpose as a quick-release skewer.

They originated in mountain biking, as QR axles occasionally broke during extreme riding, and if the quick release wasn’t properly seated, the force from the disc brakes could cause the wheel to dislodge from the dropper. They have also been used on many road bikes since then.

Secondly, Thru-Axle goes into the dropout on one side, through the hollow axle of the hub, and then screwed into the internal threads on the fork and frame on the other side. The frame and fork must be designed to use thru-axles, and you generally can’t retrofit quick-release frames for TA (except for some frames that use modular/interchangeable dropouts.)

The release on the thru-axle frame or fork is “closed” compared to the “open” release used by the QR system;

Finally, the advantages of thru-axle are:

①. Increased stiffness when turning due to larger diameter hub interface and higher clamping force. They are also more shear resistant as they are no longer limited by the 9 or 10mm diameter of QR open circuit dropouts.

②. The thru-axle allows for more consistent wheel placement compared to open trips and quick releases. Since the wheel can be held skewed in the release in the quick release, brake friction can occur due to misalignment due to the tight tolerances in the alignment of the disc brakes. The repeatability of the closed dropout system minimizes this problem.

③. Braking torque can no longer pop out of the front wheel because the axle is wrapped in the jaws.

④. Shock loads are shared more evenly between the two fork legs.

⑤. Less rotational torque on the fork legs to which the brake calipers are attached.

Unlike quick releases, thru-axles tend to be unique to each bike. Two bikes may have the same locknut distance (e.g. 142mm for a road bike), but their dropouts may be different thicknesses. Thread pitch is also a variable (spacing between adjacent thread peaks, e.g. 1 or 1.5mm). Some suspension designs also require extra long axles. Do not attempt to use an axle of a different specification than intended to avoid damage to the bike and possible personal injury.

Riders can obtain replacement thru-axles from the bike manufacturer, fork manufacturer, or aftermarket brand.