Fox Evol air sleeve review

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Full Product Name: Fox Evol air sleeve

Retail Price: £91 for the Kashima, and £57.44 for regular anodised

Available From: Mojo Suspension

Increased sensitivity on existing Fox air shocks

For 2016 Fox are offering the EVOL (extra volume) air sleeve on Float and Float X shocks, which has a larger volume negative spring to dramatically increase sensitivity on smaller bumps.

The EVOL sleeve is now available as an aftermarket hop-up for your existing shock in both Kashima finish for £91 or regular anodised for £57.44.

Fox EVOL air sleeve

The EVOL air sleeve has a characteristic bulge to house the extra air volume for the negative spring.

Although the Float shock that came as stock on my Mondraker Foxy XR Carbon felt great, I’ve found myself running the shock a little softer than I would usually to increase the sensitivity off the top and get the feel I like.

But by doing this the shock would feel a little wallowy in the mid-stroke and I would blow the O-ring off by using full travel more often than I should. Even with the biggest volume spacer, it could have felt better.

Fox EVOL air sleeve

Our Fox Float CTD shock, with the EVOL sleeve installed in place of the stock unit. Note the size of the bulge compared to the standard unit.

The EVOL air sleeve increases the size of the negative spring, which acts against the positive spring – meaning the initial force required to get the shock moving is substantially less than usual.

With the EVOL sleeve installed in place of the conventional Float sleeve, I bolted the shock to my bike- and noticed the routing for the Rockshox Reverb seat post was hampered slightly by the additional bulge on the shock body. It worked out OK once I’d adjusted the cable routing – but it’s something to factor in if you have tight clearance for your shock body.

I set the shock up with just over 25% sag  (before I was a touch over 30%) and found the initial movement of the shock to be so supple that I had to double check my sag was correct. The EVOL sleeve has such little resistance that you nearly get bike-sag!

Other than more grip and comfort over smaller bumps, what I immediately noticed was how much the bike sat up in the mid stroke compared to the previous set ups – it felt a lot more composed in G-outs and hard corners, really matching the suspension performance to the Fox 36 plugged in to the front of the bike.


Compared to the maximum volume spacer I was running previously, I’ve gone down to the smaller size and have found I only blow the O-ring off the end on those heavy head-nod landings. I’m using all but about 4mm of the shaft movement on a regular basis, with the last of it being very firm. Although this makes the end of stroke feel quite firm, the bike really does feel a lot more composed in the really rough stuff.

I’ve ridden my 140mm travel Foxy to the limit this year on proper mountain terrain, and the EVOL sleeve certainly helped me get away with questionable line choice fairly frequently!

The team at Mojo Suspension are big fans of the EVOL sleeve:

“I don’t think there’s a design out there that wouldn’t be improved by a softer start to the stroke. Obviously the shock spacers may need to be swapped to get the best feel. We find most bikes need a spacer one or two sizes down to get the best feel – though some bikes already on the largest spacer will just feel better on the same spacer if that’s still not progressive enough!”

Chris Porter, Mojo Suspension

Fox EVOL air sleeve

Although he Foxy rides brilliantly with the stock Float CTD shock, I felt it could be improved a touch and the EVOL sleeve adds the perfect touch. The shock really does add a lot of support and control to the suspension action.

I can’t find anything bad performance-wise to bring up with the EVOL sleeve – but as I mentioned earlier, the bulge in the sleeve body could be an minor issue on certain bike designs. Mondraker spec the EVOL sleeve on the 2016 model of the Foxy XR Carbon – it’s purely down to routing the Reverb cable so it doesn’t rub between the bulge and the frame.

We say

Although I’m sure there might be cases where the EVOL sleeve doesn’t work too well on certain suspension designs, I can’t imagine why any rider wouldn’t want the benefit of increased grip, better mid-stroke support and a decent progressive feel.

£91 might seem a little steep to enhance your rear suspension to some, but once you’ve tried the performance of the extra volume sleeve there’s no looking back as it’s £180 cheaper than buying the base model Anodised Float DPS shock with the EVOL sleeve already installed. 

Highly recommended.


Could your rear suspension do with a better action? 

What shock do you currently run?

Let us know below…



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