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RockShox Monarch 4.2 (09) review

SID fork's perfect rear shock match

Our rating 
4.5 out of 5 star rating 4.5
GBP £225.09 RRP | USD $309.00

Our review

Well-controlled compression and rebound, wide adjustment range and good reliability
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RockShox has often struggled with its rear shocks but its latest Monarch line for cross-country and trail bikes finally has what it takes to go toe-to-toe with the current industry benchmark, the Fox Racing Shox RP23.


Housed within the compact body of our top-end Monarch 4.2 model is essentially a miniaturized version of the Motion Control damper used in the SID fork complete with similar adjustments – Floodgate on/off, blowoff threshold and rebound speed – all accessed via high-quality machined and anodized aluminium knobs. Though the air spring switches to RockShox’s simpler Solo Air setup rather than the more complex Dual Air, negative and positive pressures are automatically equalized for the smoothest possible ride.

Not surprisingly, the Monarch provides the same ride quality out back as the SID does up front and is impressively RP23-like. Small and large impacts alike are exceptionally well controlled and the damper adjustments offer an impressively wide range. In addition, the standard air can is far less spikey than earlier RockShox renditions. If it is still a bit too progressive for your liking, there is a cleverly designed high-volume option that can be adjusted without tools to dial in your desired spring rate.

Weights are comparable as well – our 200x50mm sample is just 234g without hardware versus 244g for the RP23. The high-volume option adds another 36g.

Most impressive, however, is how much smoother the Monarch made our test bikes feel throughout the travel range, though it’s not due to any internal improvements over the RP23. RockShox fits the Monarch with its own hard anodized aluminium hardware that yields lower friction than the usual raw aluminium stuff. It rotates far easier and even presses in with less effort, with no tools required.

Downsides are few and trivial in nature. About the only thing we could come up with is the somewhat hard-to-reach rebound adjuster knob which we are almost willing to overlook in light of the handy flip-out air valve.


If you already have an RP23, the Monarch 4.2’s comparably excellent performance alone isn’t enough to justify the cost of the swap. However, those looking to upgrade from something lesser should pay the Monarch 4.2 a hard look and the hard anodized RockShox hardware (which will fit Fox eyelets) is an absolute no-brainer.

Product Specifications


Name Monarch 4.2 (09)
Brand RockShox

Description US$309-345 depending on size, plus mounting hardware, Configurations - 152 x 31mm (6.0 x 1.25), 165 x 28mm (6.5 x 1.5), 190 x 50mm (7.5 x 2.0) 200 x 50 or 57mm (7.875 x 2.0 or 2.25) 216 x 63mm (8.5 x 2.5) Weights - 234g (200x50mm, standard air can, without hardware); 270g (200x50mm, high-volume air can, without hardware) Optional high volume air can.
Additional Features Dual Flow Rebound, Hydraulic damping with IFP
Adjustable Air Spring Yes
Bushes Included No
Damping Adjustment External Rebound Floodgate
Body Material Aluminium
Body Diameter 28