H&R's PCS coilovers are one-way adjustable, with common adjustment of compression and rebound. The adjustment knob is accessible from under the car, usually with the car on the ground, and has a series of detents to aid in accuracy. The system shown is for the Audi RS4.
H&R's PCS coilovers are one-way adjustable, with common adjustment of compression and rebo
Adjustable damping coilovers are another new endeavor for H&R. It has long been H&R's position that a very good non-adjustable damper could meet the needs of almost all street drivers, but those few who demanded more became vocal enough that they could not be ignored.
H&R's PCS coilovers are one-way adjustable, with common adjustment of compression and rebound. Walter Wirtz, H&R's head of suspension development, is adamant that PCS dampers be externally adjustable, saying, "If it is adjustable, then it should be adjustable with not more than falling on the knees." The adjustment is mostly in the low-speed ranges, which affect handling and the feel of the vehicle the most. H&R finds common rebound and compression adjustment satisfactory because a greater fraction of the oil goes through the bypass and adjustments to the bypass circuit have greater effect when damping forces are high. Thus, rebound and compression adjustments are kept in proportion, despite rebound forces being several times greater.
Generally, PCS coilovers are slightly better than a very good fixed damper, except in a racing situation where one may be changing spring rates. Another case is when going from dry to wet, where a car's setup will need to be changed significantly. Changing spring rates requires disassembly of the suspension, but changing damping and anti-roll bar settings, when adjustments are available, can be done very quickly.
Walter Wirtz said he actually prefers non-adjustable dampers for street use, and to engineer. He says it is more difficult to make an adjustable damper to the same performance tolerances as a fixed damper, because each adjustment adds a bit of tolerance, and often some temperature sensitivity. Achieving the required quality and consistency of performance becomes more expensive.
PCS dampers do have a slight reduction in travel, due to the length of the adjustment mechanism internally, where there is a secondary piston for the bleed circuit that reduces extension approximately 10mm. If the end of the damper uses an eyelet, the length between the spring seat and the eyelet increases by the amount required for the adjustment knob and gear train. None of this is a problem with long, upside-down struts in front suspensions, where the only real concern is that the adjuster doesn't contact the driveshaft on a fwd car. However, it can have an effect in the rear of some cars, where travel can be long with respect to the damper body.