How to Find the Right Coil Spring for your MTB Coil Shock

In this scenario, I've input my weight while fully geared, along with the shock stroke and frame travel measurements from a Devinci Troy. The calculator indicates a spring rate of 488. However, since there isn’t a spring that matches the exact 488-pound rate, you'll need to adjust this number to fit the available spring options. You will have to choose among various spring models to round your calculated number either up or down to align with the standard 25- or 50-pound increments that springs are sold in. For instance, some spring models, such as the Fox SLS, are offered in 25-pound increments, while the majority are available only in 50-pound increments.

If you're interested in more detailed information, please check out our Auto coil spring compatibility guide.

We recommend starting with the most affordable steel spring that is compatible with your shock. Spring calculators can provide a rough estimate of where to commence, but you can't assume that the first spring you select will be the right long-term choice. It's disheartening to invest in a $130+ Fox SLS or a progressive spring only to find that the spring rate isn't suitable, necessitating an additional purchase. Therefore, we will only consider the numbers corresponding to 50-pound spring increments as a starting point.

In this example, I would look at both a 450 and a 500-pound spring rate. The 450-pound spring would feel somewhat softer, while the 500-pound option would be firmer. Personally, I would lean towards starting with the 500-pound spring because I prefer a bike that feels a little stiff rather than too soft and mushy. The calculator was purposely set to suggest slightly stiffer options to prevent the disappointment of a mushy ride right off the bat. When I tried the springs and measured the sag, the 450-pound spring settled at exactly 30% sag, confirming that the calculator's initial suggestion was a bit on the high side. However, I doubt that a 500-pound spring would have felt detrimental to my ride, but I certainly would have struggled with a 400-pound spring, which would have made my bike feel sluggish.

Let's take a look at another example. When entering my previous bike's details—a Kona Process 153—the calculator recommended a 422-pound spring rate. I opted for a 425-pound Fox SLS spring, which perfectly matched my desired sag of 30%. This instance demonstrated that the calculator worked well at the first attempt, though such accuracy is not the norm, and you shouldn’t expect your calculations to yield perfect results.