Rear Shocks

Rear Shock Buying Guide

The rear shock controls how the back end of your full-suspension bike responds to impacts, braking forces and pedalling input. Getting the right shock for your frame and riding style makes a bigger difference than most people expect.

Sizing: Eye-to-Eye and Stroke

Rear shocks are defined by two measurements:

• Eye-to-eye (E2E): The total length of the shock from centre of one mounting eye to the other, measured with the shock fully extended. Common sizes: 185mm, 190mm, 200mm, 210mm, 230mm, 250mm.
• Stroke: How far the shock compresses. This, combined with the frame’s leverage ratio, determines rear wheel travel.

These measurements must match your frame exactly. A shock with the wrong E2E won’t physically fit, and wrong stroke will give you too much or too little travel. Check your frame manufacturer’s specs before buying.

Trunnion vs Eyelet Mount

Most older frames use standard eyelet mounts (a bearing or bushing at each end). Trunnion mount shocks bolt through the shock body itself and are shorter for the same stroke length, letting frame designers run longer travel in compact frames. Your frame dictates which you need — they’re not interchangeable.

What to Check on a Used Rear Shock

• Shaft condition: On air shocks, check the shaft for scratches or scoring. A damaged shaft destroys seals and causes air loss.
• Mounting hardware: Bushings and reducers wear over time, causing knocking. Cheap to replace but check they’re included and not wallowed out.
• Damper feel: Cycle the shock slowly by hand. It should compress and rebound smoothly with no dead spots, harsh clicks, or metallic sounds.
• Air loss: For air shocks, set the pressure and leave it overnight. Losing more than 5–10 psi overnight means the seals need replacing.