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Do you remember first grade when the Circus came to town and you attended it as a field trip? There was always some excitement until the clowns came up into the audience and you freaked out. Well get your freak on kids, because here comes the Circus.
TPC (Twin Piston Chamber) is a shim-based damper that uses two independently adjustable pistons: one optimized for rebound, the other for compression. TPC is a low-pressure, high-volume system which prevents cavitation (which leads to compression spikes and stiffening) and heat-related problems. Compared to the Absolute damper, TPC is always active. A fork equipped with TPC damping will soak up even the slightest impacts. The benefit of TPC is that it allows precise control of the fork's compression damping rate. As a result, the fork can be tuned to make the fullest use of its travel while minimizing bottom-outs. Forks equipped with TPC dampers have a compression adjustment dial on the top of the right leg and a rebound adjustment dial at the bottom of the right leg. The effect of these adjustments can be easily observed when the bike is at rest and the fork is compressed.
Absolute is a platform-style damper. This means that the fork can be set to remain rigid until a certain impact threshold is exceeded. The benefit is pedalling efficiency. As proponents of rigid forks will attest, suspension has the potential to diminish pedalling efficiency by compressing the fork rather than propelling the bike forward. In the open position, the Absolute damper acts much like TPC, absorbing even slight impacts. By introducing a bit of damping platform, a rider can get the benefit of suspension without the penalty of wasted energy. In the second and third positions, the Absolute damper resists pedal bob and brake dive on smooth terrain, yet still allows the fork to move through its travel over most bumps. In the fourth and fifth positions, the fork remains rigid during most out-of-the-saddle sprints or climbs, at the expense of some harshness over washboard and rooty trails. In the sixth position, the Absolute damper locks out the suspension for everything but a major, abrupt impact, like suddenly running into a rock or log. Forks equipped with the Absolute damper have a platform adjustment dial on the top of the right leg and a rebound adjustment dial on the bottom of the right leg. The platform adjuster has a total of six positions ranging from completely open (no platform) to completely closed. The dial can be turned from one extreme to the other in about 1/3 of a turn, for easy on-bike adjustment. The effect of the various platform settings is more apparent at speed than when the bike is at rest.
Like MARS Air, ACT Air is a hybrid coil/air spring. However, while the coil and air springs in the MARS system work in series and contribute equally to the spring rate, the ACT Air system consists of a coil spring inside an air chamber. The energy of an impact is primarily absorbed by the coil spring. The air chamber provides enough adjustability to set the proper amount of sag for a given rider weight, and also contributes a certain amount of bottom-out resistance.
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