MTB rear shock springs

How to choose your MTB shock spring

Two figures are all you need to choose a spring: its length, determined by the shock, and its spring rate, determined by your weight and the frame's suspension kinematics. The rest is just material and colour.

Length, dictated by stroke

• The spring must match the shock stroke : 134, 151, 174 mm are the common metric values.
• Too short, it will not stay seated and will knock at full extension.
• Too long, it will coil bind before full stroke: the shock stops dead, and the mounting points take the impact.
• Metric and imperial lengths are not interchangeable, even when they seem close.

Spring rate

• Expressed in pounds per inch (400, 450, 500, 550…), it indicates the force required to compress the spring by one inch.
• It depends on your riding weight, the leverage ratio of the frame and your target sag.
• Aim for 25 to 30% sag in enduro, slightly less in pure downhill.
• Between two spring rates, choose the softer one if you are looking for comfort and traction, or the firmer one if you bottom out on aggressive descents.
• Most manufacturers publish a weight/spring rate chart specific to their frame: this is the most reliable starting point.

Steel or lightweight alloy

• Steel : the most common, the most durable, and by far the cheapest.
• Lightweight alloy (titanium or lightweight steel): 150 to 250 g saved in unsprung mass, but at a vastly higher price. The difference is noticeable, but it comes at a premium.

Compatibility

Coil springs are specific to each brand and often to each generation: a Super Deluxe Coil spring will not fit a Vivid or a Fox shock. Note down the exact model and year of the rear shock before ordering.

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

See also: MTB rear shocks · Shock seals and hardware · MTB shock spacers