Do you remember Gyro Gearloose? He was an anthropomorphic chicken created by the Walt Disney Company who appeared in the Scrooge McDuck comic-book series. Gyro was the town of Duckburg’s most famous inventor. Because his inventions were rarely successful, the name Gyro Gearloose has become synonymous with any inventor with a crazy or crackpot idea. Motocross has had more than its fair share of Gyro Gearlooses — some amazingly successful and others forgotten. MXA presents the latest installment in its series of weird and wacky inventions.
AIR SHOCKS THROUGH TIME
Ryan Dungey’s raced an air shock-equipped KTM 450SX early in the 2013 Supercross season. He stopped using it after the shock failed on the starting line a few weeks later.
Ryan Dungey’s WP Air shock. Dungey’s large shaft air shock was nothing new. Georges Jobe was working with KTM on an air fork and air shock system in 2001. MXA actually tested Jobe’s suspension and was very impressed with it. Jobe would later make a mountain bike version, but his motocross suspension never went into production. The FN Jobe air forks and air shock knocked 12 pounds off the KTM 520SX test mule that MXA tested.
Fox Airshox. Perhaps the best known air shock system was the Fox Airshox. It was used by virtually every rider in 1977…including factory teams. It had two air chambers. A low-pressure chamber for small bumps and a secondary high-pressure chamber for big hits. Word on the street is that WP has found a way to compensate for the air pressure gain caused by heat buildup with some type of compensating valve that changes volume as air pressure rises.
Brad Lackey on a Fox Airshox-equipped Husvarna.
1975 CZ Falta Replica with production air shocks made in Czechoslovakia.
CZ Air shock.
The only production bike to come with air shocks was the 1975 CZ Falta Replica (although Yamaha did put air forks on their bikes in 1976).
THE FN JOBE AIR SHOCK
The FN Jobe air shock.
This is the FN Jobe air shock from 2001 as tested by MXA. When George Jobe brought his radical air suspension to MXA back in 2001, he said, “I know the negatives, but I believe that at FN Jobe we have solved most of the problems. Air forks do not get as hot as an air shock, since they are not driven through the bumps, so the pressure buildup in forks is not as much of a problem.
“On the shock, I have included a series of pressure-relief valves and regulators that maintain a constant air pressure inside the shock. Our regulator system keeps the air pressure constant all the time, from the beginning to the end. We have developed a system that doesn’t require us to adjust the shock after every ride. We use both an air spring for compression and a negative air spring to control rebound.”
In essence the Jobe system was designed with a series of blow-off valves that released excess air pressure, while a regulator controlled the optimum pressure setting. There was a dial that allows the rider or mechanic to change the base air pressure setting with a bicycle pump. Even when MXA over inflated the shock on the stand, it would gasp out air when we exceeded the regulator setting. And that is what it does on the race track. As the air pressure increased with heat buildup, the shock bled off the excess pressure.