Choosing a rear shock: eye-to-eye length, stroke and Trunnion mount
Updated October 8, 2026 · Fahrradwerkstatt Avelo, Hamburg
A shock only fits if three measurements match: eye-to-eye length, stroke and mount type (standard eyelet or Trunnion). You will usually find them on your old shock or in the frame specifications. Only then do you choose between air and coil.
The three sizes that must match
Eye-to-eye length: the distance between the two mounting points, for example 210 mm or 230 mm.
Stroke: how far the shock compresses, for example 55 mm or 65 mm. Together with the frame's kinematics it sets rear wheel travel.
Mount: a Trunnion shock is bolted through the sides of its body, a standard shock through an eyelet at each end. A Trunnion shock will not fit a frame built for a standard mount, and vice versa.
| Mount | Example sizes (length × stroke) |
|---|---|
| Standard (metric) | 210 × 55 mm, 230 × 65 mm |
| Trunnion | 185 × 55 mm, 205 × 65 mm |
Air or coil?
Air shocks (Fox Float, RockShox Deluxe and Super Deluxe, Öhlins TTX Air) are lighter and are set up for any rider weight with a shock pump. Coil shocks (for example RockShox Vivid Coil, Öhlins TTX22 Coil) are very supple and stay consistent on long descents; the spring is chosen by rider weight. Air dominates in cross-country and trail; both are common in enduro and downhill.
Fitting: remember bushings and hardware
New shocks often come without mounting hardware, whose width depends on your frame. The shop stocks mounting kits, bushings and shock pumps.
Frequently asked questions
Where do I find my shock's sizes?
Eye-to-eye length and stroke are often printed on the shock or listed in the frame specifications. If in doubt, send us your frame model and year.
Can I fit a longer shock?
Only if your frame maker allows it: a longer stroke can make the rear wheel hit the seat tube or frame.
What do 2POS and Remote mean?
The shock has a lever, or a handlebar remote, to switch between an open and a firmer setting, for example when climbing.
Matching products
- Cane Creek Air IL G2 Double Barrel Trunnion air shock — £254.15
- DT Swiss Lever Trunnion R 535 ONE – rear shock — £249.89
- Formula MOD DH – rear shock — £532.09
- Fox DHX 2POS Factory – rear shock — £338.29
- Öhlins Air Trunnion TXC 1 – air shock — £164.89
- RockShox Deluxe Ultimate RCT DebonAir shock — £178.49
- Cane Creek Coil IL G2 Double Barrel coil shock — £394.40
- Cane Creek Coil IL G2 Double Barrel Trunnion coil shock — £169.99
- Cane Creek Tigon Double Barrel coil shock — £339.15
- Cane Creek Tigon Double Barrel Trunnion coil shock — £254.15
- DT Swiss R 232 ONE Lever – rear shock — £209.09
- DT Swiss R 232 ONE Lever shock — £212.49