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Fox Evolution Series Fork Upgrade

Posted on August 16 2017

The FOX Evolution Oil Cartridge has now been super-seeded, and is no longer offered in the Fox fork range. (2016 onwards). However, the good news for Fox Evolution (and RL) fork owners, is that the new FIT4 dampers are an impressive way to upgrade a Fox Evolution series fork (and many open bath RL/RLC systems too!) to massively improve that small bump responsiveness, overall tune-ability and gain a guaranteed increase in performance in every aspect of your fork's ability to perform.

The main issue with the Evolution series damper, is that it is an open-chamber system, that essentially allows oil to expel from the damper as it expands under heat, however there is no way for that oil to make it's way back in, so over time - The performance of your damper will deteriorate. A fork with the evolution series damper also requires a significantly greater amount of force required to initiate the travel, and thus a lot of users have commented on having to run lower pressures to allow the fork to move with ease. The problem with this though, is you're more than likely running too little pressure for your weight, and the fork 'bottoms-out' too easily, with little to no mid-travel stability. The Evolution damper also has a relatively basic compression circuit resulting in a very linear and un-stable feel through the travel.

Thankfully for 2016, Fox no longer use this system and ALL forks will have a fully closed FIT (Fox Isolated Technology) damper inside, with varying levels of functionality, and these dampers are compatible with 32mm, 34mm and 36mm fork options dating back to pre-2010 in some cases!

Here's just a few of the benefits of the FIT4 upgrade:


  • Greater small bump sensitivity
  • Less friction throughout travel
  • Less breakaway force required to initiate travel
  • Greater controlled oil flow through both rebound and compression cycles
  • Correct air spring pressures can be maintained.
  • External adjustability of Open, Medium and Firm
  • Long term tunability
  • Long term serviceability



Evolution 'Open-Chamber' damper vs FIT Cartridge


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