E-Bike Rear Shock Sizes: How to Measure & What Fits
Replacing or upgrading a rear shock starts with one question: what size does your bike take? Get it wrong and the shock will not fit, or it will change how the suspension works. This guide explains e-bike rear shock size in plain terms, including 9.5 x 3.0 and 185 x 55 trunnion, how to measure your bike, and which sizes HPC bikes use.
The two numbers that define rear shock size
Every rear shock is described by two measurements:
- Eye-to-eye length: the distance between the center of the two mounting points, with the shock fully extended.
- Stroke: how far the shock shaft moves as it compresses. More stroke means the shock moves further through the bike's travel.
Together they give the shock's size. A 9.5 x 3.0 shock is imperial: 9.5 inches eye-to-eye with 3.0 inches of stroke. A 185 x 55 shock is metric: 185mm eye-to-eye with 55mm of stroke. The EXT listing for a 9.5 x 3.0 shock gives the metric equivalent as 241 x 74.
Imperial, metric and trunnion mounts
- Imperial sizes, such as 9.5 x 3.0, are common on downhill and long-travel freeride bikes.
- Metric sizes, such as 185 x 55, are common on trail and enduro frames.
- Eye-to-eye vs trunnion: a classic shock mounts with an eyelet at each end. A trunnion shock replaces the lower or upper eye with a block mount that the shock body bolts into. They are not interchangeable: the frame is built for one type.
The DVO Topaz Gen 3 is available in both metric and trunnion sizes. The EXT Arma V3 is built with metric and imperial sizing, in both classic eye-to-eye and trunnion mounts.
Which size each HPC bike uses
| Bike | Rear shock size | Source |
|---|---|---|
| Trailblazer | 185 x 55mm trunnion (DVO Topaz Gen III T3 fits) | Product listing |
| Revolution W | 9.5 x 3.0 (EXT Arma MX) | HPC Revolution W specs post |
For other models, contact us with the bike and model year and we will confirm the correct size. We would rather confirm than guess. Our DVO suspension guide shows which fork and shock come on each bike.
How to measure your rear shock
- Look for markings. Many shocks list size on the body or reservoir, such as 185x55 or 9.5x3.0.
- Measure eye-to-eye. Remove the shock, fully extend it, and measure from the center of one mounting hole to the center of the other.
- Measure stroke. Measure the exposed shaft with the shock extended, or check the manufacturer's spec. The stroke must match your frame's design.
- Note the mount type. Check whether your frame uses eyelet ends or a trunnion mount, and the hardware sizes.
- Test fit. Always fit the shock and cycle it through the full travel to confirm clearance before riding. EXT also warns that dampers should be test-fit to the frame, especially on bikes with modified geometry or linkage.
Do not use a different stroke to "get more travel." On a linkage bike, a longer or shorter stroke changes the suspension's leverage and can cause the shock to bottom out or the frame to collide with parts.
Coil or air?
Both come in the sizes above. An air shock is lighter and easily tuned by changing pressure. A coil shock has a consistent, linear feel and stays predictable on long, rough descents. Our guide to downhill forks and coil shocks goes deeper.
HPC rear shocks by size
- 185 x 55mm trunnion, air: DVO Topaz Gen III T3 185 x 55mm Trunion Rear Shock, listed as fitting the Trailblazer, from $379. It has a T3 compression switch, low-speed rebound adjust, adjustable bladder pressure, and positive and negative volume spacers, and comes with a shock pump and carrying case.
- 9.5 x 3.0, coil: DVO Jade Coil 9.5x3, from $350 (Standard), $400 (Custom Tune) or $450 (Revolution Tune). The listing notes it does not include shock hardware or a coil spring, which are purchased separately. There is also a general DVO Jade Coil listing, and for that one we recommend contacting us to confirm the right size.
- 9.5 x 3.0 (241 x 74), coil: EXT Arma V3 Rear Shock, $749, custom built and tuned for your bike, rider weight and riding style, with springs in 25 lb increments.
Availability changes and some shocks are built or tuned to order, so check each product page for current stock and lead times.
Before you buy
- Confirm eye-to-eye, stroke and mount type against your current shock.
- Check the spring rate for your weight if you choose a coil.
- Ask us if your bike has a modified linkage or non-stock geometry.
If you are unsure, contact our team with your bike, year and current shock markings and we will help confirm the fit before you order.
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