72 grams can be a hell of a lot. At least for hardcore racers who weigh out the oatmeal for their morning muesli. The OVR damping cartridge from ND-Tuned is aimed at precisely this target group. For a price of 339 euros, gram-hungry riders can save another 72 grams on the Fox 32 Float SC fork for marathon use. The cartridge is also optionally available for Sid and Reba forks from Rockshox. How does ND-Tuned tickle another 72 grams out of the forks, which are already on a strict diet ex works?
The fork crown, fork tubes and stanchions remain untouched for the diet. The air chamber (left fork side) gets a modified interior, but the real difference on the scales is the damping cartridge. Normally, oil, which has to flow through different sized openings in the cartridge during compression, ensures the right compression and rebound speed, making the ride over rooty trails controllable. In suspension forks, this damping is also known as compression or rebound damping and can be adjusted using rotary knobs at the top and bottom of the right-hand fork leg. Without compression and rebound damping, suspension forks would sag when compressing and rebound so quickly that the tyre loses contact with the ground. So there is no saving on the function itself, but because oil weighs 870 grams per litre, the Portuguese only press air (1.2 grams per litre) instead of the viscous liquid through their OVR (Opening Valve Resistance) damping cartridge. In addition to the weight reduction, the OVR cartridge should also prevent annoying bobbing of the fork when pedalling and reduce maintenance - so much for the theory.
In practice The setup works the same for both rivals. We filled the forks with 75 PSI each (right fork leg) and adjusted the rebound accordingly. After the first ride on the singletrack, however, the differences become clear. While the original fork with oil damping willingly smacks away all bumps and glides over root carpets and small stone fields in a comfortable and controlled manner, the counterpart with air damping has a little more trouble. No matter how high we set the breakaway torque of the OVR cartridge, the ND-Tuned version does not want to work as elegantly as the original. The lightweight fork is less responsive and works much firmer. When pedalling in the saddle, both forks bob equally little. Our suspension fork test rig, developed by the Zedler test institute, underlines the impression from practice and even measures four millimetres less travel on the tuned version.
The bottom line: The ND Tuned cartridge works in principle, but cannot hold a candle to the original from Fox. The air cartridge offers an alternative for tuners who haggle over every gram and mainly ride in moderate terrain. In view of the surcharge of 339 euros, however, weighing oatmeal is cheaper.
WHAT THE TESTERS SAY
Stefan Loibl, BIKE editor:
I'm not prepared to accept the loss of damping for a 72 gram weight saving. The standard fork responds more sensitively and dissipates energy more harmoniously during compression. There is no reason for me to change.
Ludwig Döhl, BIKE editor:
Anyone who also likes to ride single trails on their cross-country bike will be happier with the standard cartridge from Fox. It is clearly superior to the OVR cartridge off-road. The OVR cartridge is a product for gram-foxers who rarely leave the gravel track.
Peter Nilges, BIKE Test Manager:
The technology of ND-Tuned has a promising future. However, there are clear limits to air damping. In addition, the setup with a separate air chamber is more complex. There is a reason why all standard suspension elements are damped with oil.
Fox 32 Float SC 100 mm / 29"
Price 1159 Euro
Weight 1345 grammes
Stiffness Twisting 14.4 Nm/°
Setting option Spring rate, rebound, low-speed compression, three platforms
Fox 32 Float ND-Tuned 96 mm / 29"
Price 339 Euro (cartridge only) | 1498 Euro (whole fork)
Weight 1273 grammes
Stiffness Twisting 14.8 Nm/°
Setting option Spring stiffness, rebound, OVR release hardness
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