Rider Weight Spring Rate Calculator
Calculate the ideal coil spring rate for your mountain bike or motorcycle suspension based on your weight and frame geometry.
Recommended Spring Rate:
Metric Equivalent: 0 N/mm
*Note: Always round to the nearest available spring increment (usually 25 or 50 lbs/in).
Understanding Spring Rate and Suspension Sag
Choosing the correct spring rate is the single most important adjustment you can make to your coil-sprung suspension. Whether you are riding a downhill mountain bike or a motocross bike, the spring rate determines how the bike sits in its travel (sag) and how it responds to impacts.
What is Spring Rate?
Spring rate is the amount of force required to compress a spring by a specific distance. In the imperial system, this is measured in lbs/in (pounds per inch). In the metric system, it is measured in N/mm (Newtons per millimeter). A 500 lb spring requires 500 pounds of force to compress it exactly one inch.
Why Weight Distribution Matters
Your total weight isn't distributed evenly between the front and rear wheels. For most mountain bikes, especially during descending, roughly 60% to 70% of the rider's weight is supported by the rear shock. Our calculator uses a default of 65%, but you can adjust this based on your specific bike's geometry or riding style.
The Role of Leverage Ratio
The leverage ratio is the relationship between how much the rear wheel moves compared to how much the shock moves. It is calculated as Total Wheel Travel / Shock Stroke. A bike with 150mm of travel and a 50mm stroke shock has a leverage ratio of 3.0. A higher leverage ratio requires a stiffer spring to support the same rider weight.
Realistic Example
Imagine a rider who weighs 180 lbs with 15 lbs of gear (total 195 lbs). They ride an enduro bike with 160mm (6.3″) of travel and a 62.5mm (2.46″) stroke shock. They want 30% sag.
- Total Weight: 195 lbs
- Leverage Ratio: 6.3 / 2.46 = 2.56
- Weight on Rear: 195 * 0.65 = 126.75 lbs
- Required Spring: (126.75 * 2.56) / (2.46 * 0.30) ≈ 441 lbs/in
In this scenario, the rider should look for a 450 lb spring.
How to Verify Your Rate
After installing your recommended spring, you must check your Sag. Sag is the amount the suspension compresses under your weight in a neutral riding position. If you have too much sag, you need a firmer spring. If you have too little sag, you need a lighter spring. Avoid using more than 2 turns of "preload" on a coil spring to compensate for a light rate, as this can lead to coil bind and poor small-bump sensitivity.