We’ve been fans of RockShox forks with Dual Air spring for a long time, so it made perfect sense to us when they introduced the system to their top-of-the-line Monarch rear shock.
The system uses two air chambers working in opposition. This makes the shock much more supple through the first part of the travel, because compression is assisted. Negative air springs aren’t new, but independent adjustability is, allowing tuning of both sensitivity and the spring rate.
With minimal and matched negative and positive spring pressure, we got a fairly linear and supple action. Whacking in a load of positive pressure, the shock really ramped up through its travel, but retained the small bump sensitivity and sag we wanted by charging more pressure in the negative chamber than the positive.
The negative air chamber has a very small capacity, so is difficult to set accurately. A tiny amount of air equates to a big pressure difference, and we used a check-valve adapter on our pump for accuracy.
After spending some time experimenting with different ratios of positive versus negative air pressure, we were really reaping the rewards. We got the shock to feel nearly as supple as a coil sprung shock over small bumps, yet could tune in that super-useful ramp-up to stop the bike wallowing in its travel through G-outs and berms.
The Dual Flow rebound damping stroke copes superbly as the spring rate changes through the travel. The initial rebound stroke is adjustable and can be set to really follow the terrain over high speed, small bumps, giving bags of traction. Give the bike a good wallop at speed and there isn’t a trace of bucking, because it absorbs and controls the forces consistently well.
The effective low speed compression floodgate is externally adjustable and switchable. We wound on loads of damping to get the bike to sit up on climbs, yet as soon as things sped up and the bike got into its travel we could hardly even notice the floodgate intervening. When we flicked the lever to turn the floodgate off the bike became super-active, allowing us to push it into turns and plough through rocks with superb control.
Our shock was custom valved for the bike, and we would definitely recommend this. We did try an initial pre-production shock and it took a couple of different shim stack tweaks to get things running exactly the way we wanted them.