MTB shock

MTB Shocks: Coil or Air, Eye-to-Eye Length and Stroke

The shock is the suspension element in your mountain bike's rear triangle: The spring supports your weight, while the damping controls how fast the rear triangle compresses and rebounds. At MTB-Raceshop, you will find coil and air shocks from PUSH Industries, Öhlins, and Vorsprung.

A new shock only fits if the eye-to-eye length, stroke, and mount exactly match your frame. We explain how to check this further below.

Coil vs. Air Shocks Compared

Coil Shocks

Steel spring plus damping: very sensitive, lots of grip, and consistent on long descents. You determine the stiffness via the spring rate. Available from us: PUSH ELEVENSIX, VT/X and SV8, Vorsprung Telumand Öhlins TTX22M.2.

Air Shocks

Lighter, adjustable to your weight using a shock pump, and progression adjustable via volume spacers. For trail and enduro, we carry, for example, the Öhlins TTX1Air m.2and the TTX2Air.

XC Shocks

Lightweight air shocks for short travel, often with remote lockout. The Öhlins TXC1Airis designed for XC bikes with little travel, the TXC2Air for XC bikes with a less progressive rear triangle.

Whether a coil shock fits your bike depends on the rear triangle: it needs sufficient progression to prevent bottoming out and enough space for the spring in the frame.

Shock Dimensions: Eye-to-Eye Length and Stroke

MTB shocks are specified with two numbers, for example, 210 × 55 mm:

• Eye-to-Eye Length: Distance from bolt centre to bolt centre on the uncompressed shock.
• Stroke: How far the shock can compress. Together with the rear triangle kinematics, it determines the travel at the rear wheel.
• Common sizes are 185 × 55, 205 × 65, 210 × 55, or 230 × 65 mm. Older frames sometimes use imperial measurements like 8.5 × 2.5 inches (216 × 63 mm).
• Many shocks can be internally converted to less stroke, such as the Vorsprung Telum or the PUSH VT/X in 2.5 mm increments.

Trunnion or Standard Eyelet: How the shock is mounted

Standard Eyelet

There is a shock eyelet with a bushing or bearing at both ends. Mounting hardware accounts for the width of the frame mount and the bolt diameter.

Trunnion

The shock body is bolted directly into the frame via two lateral threaded studs. This saves length: for the same stroke, a Trunnion shock is 25 mm shorter, e.g., 205 × 65 instead of 230 × 65 mm.

Bike-Specific Shocks

Some shocks are only available for specific frames, for example, the Öhlins TTX22Mfor the Specialized Enduro and Kenevo. You select the PUSH ELEVENSIX directly according to the bike model.

You can find matching hardware, roller bearings, and needle bearings under Mounting Hardware, and FixShox bushings at DHsign.

Adjusting and Servicing MTB Shocks

Start with the SAG, i.e., the compression under your weight in the riding position. RockShox recommends 25–30% for coil shocks; your bike manufacturer specifies the exact value. Afterwards, adjust the rebound and compression damping to your terrain and riding style.

For coil shocks, the spring rate determines the SAG. Our Spring Calculatorprovides a starting value, and you can find matching steel springs under Springs.

We service shocks from FOX, RockShox, and Öhlins; PUSH shocks are serviced via the European PUSH Service Centre. You can send the shock by post or drop it off in Dällikon by appointment.

To Shock Service

Frequently Asked Questions about MTB Shocks

How do I find out the dimensions of my MTB shock?

The eye-to-eye length and stroke are usually printed on the shock body or listed in the frame manufacturer's data, e.g., 210 × 55 mm. You can also measure the eye-to-eye length from bolt centre to bolt centre. You also need to know the mount (Standard Eyelet or Trunnion) and the bushing dimensions.

What is a Trunnion shock?

In a Trunnion shock, the mount consists of two lateral threaded studs located directly on the shock body. As a result, it is more compact than a shock with a standard eyelet for the same stroke. Trunnion and standard shocks are not interchangeable.

Can I replace an air shock with a coil shock?

Often yes, if the dimensions, mount, and space in the frame fit, and the rear triangle has sufficient progression. Also, check whether the frame manufacturer approves coil shocks. Send us your bike model, model year, and frame size, and we will check it for you.

Can I install a shock with more stroke?

Only if the frame manufacturer approves the longer stroke. More stroke means more travel at the rear wheel—without approval, the tyre may hit the frame or the shock may collide with the frame. Less stroke can be set on many shocks using spacers.

How often does an MTB shock need servicing?

For air shocks, RockShox recommends an air sleeve service every 50 riding hours and a full service after 100 or 200 hours, depending on the model. FOX recommends 125 hours or once a year, PUSH recommends 12 months. You can book the Shock Servicedirectly with us.