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Fox Fork Axles Explained

Posted on December 24 2021

 

Fox have produced varying axle systems and types over the years, and we've created this little blog to help you identify the differences between them. Fox's axles have rarely been interchangeable between models, and hopefully this little guide is helpful.
 
2021 - Kabolt 'X' Axle P/N 820-09-071 here.
Works with 2021 and 2022 Fox 36 and Fox 38 forks. The Kabolt system does away with the axle/hub alignment system as found on the normal QR axle for 2021, but it is preferred in many ways due to its simplicity and hex bolt security. It relies on adequate tension through the 6mm Hex upon installation. When using this Kabolt-X system, you need to use the circular washer as supplied in the kit, instead of the keyed shim that comes standard in a fork originally with QR15.
 
2021 - 15 QR (15x110 Boost) Axle P/N 820-09-063 here.
Compatible with all boost Fox forks from 2016 (when 'Boost' was first released), however this axle was only introduced in 2021 with the release of the new chassis 36 and 38. It features the 4mm hex tension adjustment within the axle internals, and hence is designed for use with forks that do not have the axle hardware (803-00-370) adjuster on the drive side. The axle tension adjustment allows for the QR lever to be properly tensioned for when closed.
 
2016-2020 15QR (15x110 Boost) Axle P/N 820-09-013 here.
Compatible with boost Fox forks from 2016 (when 'Boost' was first released), except for the 2021+ 36 and 38, and forks without the axle hardware (803-00-370). It has no tension adjustment for the QR lever, and hence is designed for use with forks that have the axle hardware (803-00-370) adjuster on the drive side. The axle hardware allows for the QR lever to be properly tensioned for when closed.
 
2016-2020 15QR (15x110 Boost) KABOLT Axle P/N 820-09-019 (black) and 820-09-023 (orange) here.
 
Compatible with boost Fox forks from 2016 (when 'Boost' was first released), except for the 2021+ 36 and 38, and forks with or without the axle hardware (803-00-370). It relies on adequate tension through the 6mm Hex upon installation. 
 
2016-2020 15QR (15x100 NON Boost) KABOLT Axle P/N 820-09-018 (black) and 820-09-022 (orange) here.
 
Compatible with non boost Fox forks from 2009 (except 29" or bolt-up axle early 36 models), and suitable for forks with or without the axle hardware (803-00-370). It relies on adequate tension through the 6mm Hex upon installation.
 
2009-2021 15QR (15x100 NON Boost) Axle P/N 820-09-014 here.
 
Compatible with non boost Fox 32, 34 forks using the 15mm axle system, introduced in 2009. It is also compatible with select Fox 36 27.5" non-boost models from 2015. It has no tension adjustment for the QR lever, and hence is designed for use with forks that have the axle hardware (803-00-370) adjuster on the drive side. The axle hardware allows for the QR lever to be properly tensioned for when closed.
 
2015-2017 Fox 36 15x100 Axle 
  • 820-09-005 (axle only) here.
  • 820-09-029 (axle with hardware) here.

The 2015 chassis update to the 36 brought with it a funky new interchangeable axle system, allowing riders to pick between the 15 or 20mm axle options, forks often came with the options for both. The lower leg used 2 spacers within the circular dropout for the 15mm axle suitability, combined with 1 (very specific) locating shim on each side. It was a bolt up system using a 5mm hex key. 4 pinch bolts seen from the front clamped down on the axle for increased chassis stiffness, and axle security.
 
2015-2017 Fox 36 20x110 Axle 
  • 820-09-004 (axle only) here.
  • 820-09-028 (axle with hardware) here.
 
The 2015 chassis update to the 36 brought with it a funky new interchangeable axle system, allowing riders to pick between the 15 or 20mm axle options, forks often came with the options for both. The lower leg used 0 spacers within the circular dropout for the 20mm axle suitability, combined with 1 (specific to the 20mm axle system) locating shim on each side. It was a bolt up system using a 5mm hex key. 4 pinch bolts seen from the front clamped down on the axle for increased chassis stiffness, and axle security.
 
 
2004-2022 Fox 40 20x110 Axle P/N 802-00-024 here.
Fox's longest running axle that still features in the range. Back in 2004 when the Fox 40 was released, this axle was used in conjunction with the 4-pinch bolts. It was a bolt up system using a 5mm hex key. The 4 pinch bolts seen from the front clamped down on the axle for increased chassis stiffness, and axle security. This system remains the same as of today in the Fox 40 and bomber 58 models. 
 
 
2005-2014 Fox 36 20x110 Axle 
Originally released with the first generation 36, which was 20mm only for it's first few years. The early generation 36 20mm axle is no longer available, but can be substituted with the Fox 40 axle as above, as long as you don't mind it protruding 5mm further out than it should.
 
Note, all early versions of the 20mm axle system are 20x110. Newer systems seen in the 2019+ Fox 40 models use the same axle, but are referred to as 20x110 Boost. This refers to the brake spacing, which is 5mm further out, allowing for hubs to be built with a wider flange for a stiffer wheel build.