The chain on a full-suspension mountain bike constantly has an effect on the performance of its suspension and, since Aaron Gwin made that astounding chainless win at Leogang in 2015, brands have been looking to mitigate any influence. Now Fox has entered the fray, publishing a patent on a rear hub and derailleur system that decouples.

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It's not just general suspension performance that's sought after, however. As rear suspension moves through its travel, the chain effectively grows which then pulls back on the chainring, resulting in what's known as pedal kickback. This can be found especially when riding through rock gardens and similar technical sections at high speed. To reduce this effect, brands such as Forbidden, Deviate and Cannondale have created bikes with idler pulleys or high pivots - but of course, these bikes are a touch weightier (generally) and require more maintenance.

2023 fox decoupling mech hero.jpg, by Liam Mercer

However, Fox has taken a different approach and has designed an automatic decoupling hub paired with a derailleur with an automatic clutch. The former uses electromagnets to disengage the freehub's pawls and allows the freehub to coast with the aim of improving suspension performance. 

Then the idea behind the automatic clutch on the derailleur is that it'll switch off under high-speed impacts, allowing the suspension to move more freely again. Of course, under pedaling both of these systems will engage and the clutch will switch back and operate as intended. 

Whether this tech will be useful to the average rider is arguable but its use during race scenarios could change the game. Let me refer back to that Aaron Gwin win - it could be said that the improved suspension performance as a result of the missing chain could have had some influence on his win. However, a shift in mindset (knowing he has to work the bike very differently) could have been a factor in earning him that podium position.

Of course, this tech would be very useful in enduro situations where stages combine extreme downhill sections with long, pedal portions.

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