How to choose your MTB wheel retention system?

Seemingly quite an inconspicuous part, the wheel retention system or wheel clamp ensures your wheels are properly secured. As such, it must be selected carefully, as otherwise you will not be able to fit your wheel.

Standards

The dimensions of the front wheel axle: 9x100 mm, 15x100 mm, 15x110 mm Boost, 15x110 Predictive Steering, 20x110 mm or Lefty (for Cannondale forks of the same name only).
Rear wheel axle dimensions: 9x135 mm, 12x135 mm, 12x142 mm, 12x148 mm or 12x150 mm.
Types of mounting: quick-release (QR) or thru-axle.

Types of wheel retention systems

Type "quick-release": Commonly known as 9 mm or QR (for Quick Release), this retention system has the distinctive feature of remaining fitted to the wheel even when it is no longer on the bike. The skewer itself has a standardised diameter of between 4 and 5 mm.
Note: For the rear wheel, however, it measures 10 mm despite being referred to as 9 mm.

Simple, lightweight and quick to install, as its name suggests, this type of retention system is reserved for leisure use due to its lack of rigidity and robustness.

Type "thru-axle" : This component, which acts as the axle for the wheel, screws directly onto the frame or fork. As such, it is removed from the wheel when it is taken off the bike.

There are several diameters: 15 or 20 mm for the front wheel axle; and 12 mm for the rear axle. Regarding the length, this is measured between the fork or frame dropouts. For the front, the most common standard is 15x100 mm, and 20x110 mm for more aggressive disciplines. For the rear it can be 135, 142 or 150 mm and there are several formats: the "X-12" type, recognisable by a 1.0 mm thread pitch (very fine). The "Maxle" type, identifiable by a 1.75 mm thread pitch (relatively coarse). And finally the "E-Thru" type, with a thread pitch of 1.5 mm. Note that certain frame brands develop their own axle standard which is therefore not compatible with these three classics.

Beyond this multitude of standards, new MTB frame geometries and the use of increasingly wide tyres have forced manufacturers to develop new standards. Thus some bike models require axles extended by a few millimetres called "Boost". Furthermore, some forks require specific axles — this is notably the case for the Cannondale Lefty and Lefty Supermax, as well as the RockShox RS-1.
Finally, you may also come across a 9 mm thru-axle called "Thru Bolt", specific to certain DT SWISS wheel models.

Increasingly widespread, thru-axles offer significantly better rigidity, particularly in torsion, and outstanding robustness.

Which wheel retention system should you choose?

The choice between a quick-release or a thru-axle, as well as its dimension, may be dictated by your frame and/or fork model. You must therefore first check the mounting system compatible with your components. Even though there are adapters that will allow you, in most cases, to opt for a different axle length from the one you had previously.

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