One of the best ways to customize and fine-tune the feel of your mountain bike’s suspension setup is by choosing the right spring for your rear shock. We carry a full lineup of rear shock springs from major brands including Fox Racing Shox, RockShox, Cane Creek and MRP. Rear shocks that use air springs — which are most popular among XC, trail and other short-travel suspension systems — don’t have the option of swapping out springs. You can adjust and service an air spring shock, but you can’t actually replace the spring itself. Coil spring shocks, on the other hand, use metal springs that can be changed and tuned to address variables such as rider weight, terrain, and the type of suspension system on your bike.

Coil springs are typically made from either steel or titanium. Both perform the same duties, with a similar feel, but titanium is lighter (and more expensive). Before deciding which spring you want, you’ll need to know a few measurements and technical details. The first is shock stroke length, which refers to the travel of the shock itself from unloaded to fully compressed. This is different than the actual suspension travel on your bike (which refers to rear wheel travel). You’ll also need to know spring length, which is often printed right on the spring. These figures refer to weight (in pounds) needed to compress the spring one inch (aka spring rate) and the length of the spring in inches. An example would be 400 x 2.5.

Finding the perfect spring rate depends on your weight, riding style and terrain. You want a rear shock spring that gives you the right amount of sag, which is how much the suspension compresses when you’re sitting in the saddle. A general rule of thumb for sag is to have ¼ the total amount of travel on an XC or trail bike, and 1/3 for a DH bike. This can vary depending on your riding style, but it’s a starting point. Once you’ve narrowed down your options for rear shock springs that will work for your bike, feel free to call one of our Gear Advisors at 888-880-3811 to answer any questions and help you find the right one.