HOW IT WORKS Because the Curnutt valving system is incredibly simple (one-fifth the parts of a typical washer-stack piston), it is difficult to explain its operation with words alone Click Here For A Diagram
Anyone who follows the downhill scene has heard or seen the Curnutt shock. Brent Foes and Charles Curnutt Jr. have been developing the revolutionary damper for the past four years in relative obscurity, but now, the floodgates have opened on their new damping technology, I figured that it’s time to tell the complete story.
The Curnutt shock was invented by Charlie’s dad, Charles Curnutt Sr., who designed the position-sensitive compression valve to keep off-road racing cars riding level through fast corners. The valve has a blow-off feature that can be externally tuned with simple air pressure. Once the bump energy exceeds the compression valve’s threshold pressure, it cycles easily. Charlie Sr. may have intended his compression valve for car suspension, but when Brent Foes got wind of it, he immediately recognized that it could prove to be the holy grail of mountain bike monkey motion.
It was Charlie Curnutt Jr. who approached Brent with the concept of adapting the air-powered compression valve for mountain bikes. Foes is no stranger to the difficulties of developing a raw concept into a tool that can win World Cup races and Curnutt heralds from Honda Motor Corporation’s suspension development shop. Both are perfectionists, so it is no surprise that they spent almost four years tweaking the shock before they proclaimed it fit for sale. Don?t get into a huff yet, though–presently the shock will be offered as an upgrade to 2001 and up-coming 2002 Foes DH Mono chassis.
HOW THE SHOCK RIDES I had a chance to test the team’s only spare 2002 Foes DH Mono at Snow Summit, the site of the previous NORBA National. (read the full test in the up-coming MBA) and was impressed by the shock. If you have ever pedaled a Foes DH racer, you?ll know that it is one of the slower-accelerating of the breed. The Curnutt shock converted the Foes into one of the best pedaling DH machines that I have ever thrown a leg over. In the rough, the suspension remained in the middle of its travel, while sucking up everything in its path. Too much to believe?
What if I said that anyone who can operate a shock pump and a couple of clickers, can fine-tune the high and low-speed damping of the Curnutt shock?while it’s on the bike. Yeah, it works. I switched back to the stock, Fox Vanilla RC shock (the reigning superdamper) and realized the benefits right off. The conventionally valved Fox blew through its travel easily, and the bike felt far more unsettled?especially through the corners.
There is no bottom-out bumper on the Curnutt shock. As the shock shaft plunges into the body, it raises the internal pressure?and increases the compression damping. This feature is adjustable with a red knob on top of the shock. The main compression damping is set with air pressure in the compensation chamber. The more pressure, the greater the compression damping forces. That’s the simplicity of the system. Conventional shocks require a complete disassembly to accomplish a single readjustment?a Foes/Curnutt pilot can do all of this mid-way through a DH run. Rebound damping is adjustable with a conventional clicker.
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