Recent years saw the introduction of hollow axles, as the pipe is the stiffest construction for it's weight for loads expected on an axle.

And now the industry is introducing the 12mm solid rear axle. Solid. Why solid? Why not standardize both axles to be 9, 15 and 20mm and be done with it?

  • 2
    I can only speculate than in 2-3 years time the industry will "invent" the hollow rear axle. However, I have faith that the bike market competative, at least when hubs and frames are concerned!
    – Vorac
    Sep 26, 2014 at 8:27

1 Answer 1


If you mean 12mm thru axles, they have been around for a few years now but in different guises depending on hub and frame spacing standards.

• 150x12mm
• 142x12mm
• 135x12mm

With the rise of enduro/am/do it all style mtb It's about creating harmony between weight, stiffness and ease of use. and a standard going forward that can adhere to modern frame and hub design trends.

The main advantage of 12mm thru axle is that through axles enable you to get a more secure connection between frame and wheel as the axle goes through the hub and almost always then screwed into the frame.

The 15mm and 20mm axle standard is geared up more for Forks. and some come as proprietary technology specific to a fork manufacturer.
Also depending on your riding style and frame dropouts 9mm qr can be weak and flexy thus a 10mm bolt up conversion may provide appropriate strength/rigidity for older frames.

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