MTB Rear Wheel Axles

How to choose your MTB rear thru-axle

The rear axle passes through the frame dropouts and screws into place. Its length and thread pitch therefore depend on the frame, not on the wheel or rear derailleur.

Spacings

• 12x148 mm Boost : the standard for recent MTBs, from XC to enduro.
• 12x142 mm : the previous generation, still very common.
• 12x157 mm Super Boost : certain enduro and e-MTB models, to increase wheel stiffness and tyre clearance.
• 9x135 mm quick release : older MTBs.

Total length and thread pitch: the two pitfalls

Two frames listed as 12x148 mm may require two different axle lengths, depending on dropout thickness and thread depth. The thread pitch also varies: M12x1.0, M12x1.5 or M12x1.75 depending on the brand. The safest approach is to measure the original axle—total length and thread length; failing that, check using the exact frame model—Burgtec categorises its axles by brand and model.

Lever or Allen key?

• Lever : tool-free removal, handy for a puncture on the trail.
• Allen key : lighter and with nothing protruding on the drivetrain side.
• DT Swiss RWS : adjustable lever that is torqued down and then tucked along the chainstay.

When tightening

Comply with the torque specified by the frame manufacturer. An over-tightened axle distorts the dropouts and makes removal difficult; if not tightened enough, it develops play and damages the frame threads—a repair far more costly than a new axle. Clean and lightly grease the threads each time you reinstall it.

To find out more: How to choose your MTB wheel skewers

See also: MTB front thru-axles · MTB derailleur hangers · 29-inch MTB wheels