MTB Rear Shocks

How to choose your MTB rear shock

Unlike a fork, a rear shock is not chosen primarily by its range level, but by its dimensions. A top-tier shock with the wrong fitment will not fit, or will fit improperly. Always check the dimensions before looking at anything else.

Dimensions, before anything else

• A rear shock is defined by eye-to-eye × stroke : 210x55, 230x60, 190x45 in metric.
• Older frames use imperial : 7.875 x 2.0 inches, for example. The two sizing systems are not interchangeable.
• Mounting Trunnion mounts the upper body via two side bolts into the shock body, and uses dedicated dimensions (185x55, 205x60, etc.).
• A 5 mm error in stroke changes the rear travel and can cause frame bottom-out or, conversely, prevent you from using full travel.

Air or coil

• Air : lightweight, finely adjustable to your weight, and progression can be fine-tuned using volume spacers. The standard choice from XC to enduro.
• Coil : outstanding small-bump sensitivity and consistent behaviour from the first to the last corner of a long descent. Requires the correct spring rate and accepting 400 to 600 g of extra weight.

The tune, the overlooked specification

Every frame has its own kinematics and leverage ratio. Manufacturers supply their shocks with an internal tune matched to a specific kinematic profile, designated for example as M/M or L/M for compression and rebound. A shock with the right dimensions but the wrong tune will bolt on perfectly yet perform poorly: either too firm, or unable to control rebound properly. Always check the original shock's tune or the one recommended by the frame manufacturer.

Available adjustments

• Rebound : featured on all shocks, this is the baseline adjustment.
• Low-speed compression : controls pedal bob and chassis pitch under braking/support.
• High-speed compression (RC2 models): controls harsh impacts, jump landings, and fast root hits.
• Hydraulic Bottom Out : progressive damping at the very end of the stroke, found on recent Vivid and Super Deluxe shocks.
• Lockout or climb switch : useful in XC and marathon, unnecessary in enduro.

Electric mountain bike

The weight and speed of an e-MTB put greater demands on the rear shock, which runs hotter and wears faster. E-MTB tuned versions feature adapted damping and seals: on this type of bike, it is not marketing hype, but a genuine necessity.

To find out more: How to choose your MTB rear shock

See also: MTB rear shock springs · Shock seals and bushings · MTB shock spacers