2014 Fox 40 Float RC2 & DHX RC4

Mountain Biking Magazine


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2014 Fox 40 Float RC2 & DHX RC4

Over the past two years the engineers at Fox have been working hard with their top riders to come up with something special, and the new air sprung 40 Float RC2 forks and DHX RC4 rear shock are the fruits of that labour.

Float 40 gallery

The new air sprung 40 has been completely reworked from the ground up. As you’d expect, the removal of a coil spring has automatically made this fork lighter than ever, but with a redesign of almost every single other component the fork is even lighter than you’d expect. At just a fraction under 6 lbs this fork is over a whole pound lighter than the 2013 40. Out of pure curiosity we also weighed a pair of the very first Fox 40’s which we have kicking around the office and those weighed nearly 2 lbs more than this new fork!

The full breakdown of the weight savings is as follows:

Air Spring: -152g
Lower Leg Casting: -150g
Upper Tubes: -89g
Upper Crown: -45g
RC2 Damper: -24g
Lower Crown: -18g
Steering Stop Bumpers: -4g

As you can see the new lower leg design have saved almost the same amount of weight as removing the coil spring, and the butting of the upper tubes has also saved a fair old chunk too. Of course though, weight saving is all well and good, but can this new air fork rival the coil 40? Well the guys at Fox seem to think so, and Deputy Editor Steve Jones has only recently got back from a sunny trip where he got to test them out himself. It’s obviously too early to draw any final conclusions, especially as these forks will have received royal treatment and will certainly not be ‘off the shelf’ units (as with most forks that we get to test out), but he did say that a couple of improvements were definitely noticeable.

The first is that the new chasis is more compliant, which is definitely a good thing. Don’t think that it’s not precise though, that’s just the same as before, as is the overall strength, but now there’s definitely a bit more ‘give’ which helps to reduce feedback to the bars. The other thing that he noticed is that there’s none of that knocking feeling mid stroke which we’ve so often had on previous 40’s. The ability to dial in the correct pressure and spring rate (nine settings are available) is also a welcome bonus.

Fox reckon they have spent a lot of time getting the negative spring system right (a titanium coil spring) and the result is that they’ve ended up with a very supple and linear first half of the travel and then the progressivity ramps up as you go deeper into the travel. The level of this progressivity can be adjusted internally to one of nine different settings. The nature of the air spring differs from that of the coil spring so much that Fox have also had to rework the RC2 damper. Years ago we all seemed to be crying out for linear springs (and therefore coil), but it seems that now we often want a more progressive feel and to achieve this with a coil spring you have to rely on the damping to mimmic this, but with this air spring Fox reckon that less is actually asked of the damper, and therefore it can be made to perform better. The natural ramping up at the end has also meant that Fox have been able to do away with the hydraulic bottom out control. To reduce friction as much as possible Fox have even given the damper shaft a Kashima coating.

Adjustments on the damping side are as before, i.e. you get externally adjustable high and low speed compression and rebound damping. There are however a couple of other small changes and those are that on the back of the legs just underneath the seals you now get a push button air bleed port to remove any built up pressure within the fork, and Fox have done a slight tweak to the design of the axle pinch bolts. All in all then these forks really do look to be very promising indeed, which should make this year even more interesting in terms of DH forks than we already thought it was going to be…plus these are also 650b compatible thanks to two size specific lowers, so that opens up another door…

DHX RC4 gallery

The other new product which is being launched today is the latest incarnation of the DHX RC4 rear shock. It comes as little surprise to hear that this shock has been designed to work in harmony with the new fork. The main improvements that Fox set out to make though were to improve the damping performance and increase responsiveness and sensitivity.

On the damping side Fox reckon that frames are now tending to be made with more natural progressiveness built into the suspension design, which in tern means that they feel that they can now offer a more linear shock tune. Like the fork damper this means that the shock can be left to concentrate on pure damping work rather than also having to deal with adjusting the progressivity of the suspension. The addition of Air Assist and Air Assist Volume adjusters instead of the ‘Boost Valve’ does allow you to adjust the progressivity of the shock though, much like the fork, it’s just that now the damping is not expected to carry out that work.

The sensitivity of the shock has mainly been increased by reducing the diameter of the shaft from 5/8″ to 1/2″. This reduces friction and it has the added benefit of allowing more room for oil.

Adjust wise, apart from the Air Assist, the shock remains largely as before with externally adjustable high and low speed compression and rebound damping. So, perhaps less of a reworking than the forks, but the changes should be noticeable nonetheless.

And finally, for those that like to see behind the scenes here are some photos of the development of the new fork…



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