YSS Spring Rate Calculator
Calculate the ideal spring rate for your YSS suspension based on rider weight and bike geometry.
*Note: This is an estimation. Always consult the YSS catalog for specific shock model compatibility.
Why Spring Rate Matters for YSS Suspension
Selecting the correct spring rate is the single most important step in setting up your YSS shock absorber. The spring's primary job is to support the combined weight of the motorcycle, rider, and gear while maintaining the suspension within its optimal working range (the "sweet spot").
If your spring is too soft, the suspension will sit too low in its travel (excessive sag), leading to frequent bottoming out and harsh handling. If it is too stiff, the bike will feel unresponsive, lose traction over bumps, and fail to use its full travel.
How to Use the YSS Spring Rate Calculator
To get an accurate result, you need to input several key metrics:
- Rider Weight: Always include your helmet, leathers, boots, and gloves. This usually adds 7-10kg to your body weight.
- Leverage Ratio: This is the ratio between rear wheel travel and shock travel. Most modern bikes range between 2.0:1 and 2.8:1. If you are unsure, 2.0 is a common middle ground for twin-shock setups, while 2.5 is common for mono-shocks.
- Wet Weight: The actual weight of the bike with all fluids and fuel.
Understanding YSS Spring Markings
YSS springs usually have a code printed on them, such as 46-25-35-200. Here is how to read it:
| Code Part | Meaning |
|---|---|
| First Number (e.g., 46) | Inside Diameter of the spring (mm) |
| Second/Third Number (e.g., 25-35) | Spring Rate (N/mm). Progressive springs show two numbers. |
| Last Number (e.g., 200) | Free Length of the spring (mm) |
Linear vs. Progressive Springs
For most track and performance street applications, YSS recommends linear springs (constant rate). However, for touring bikes that carry varying loads (riding solo vs. with a passenger), a progressive spring might be suggested to provide comfort on small bumps while resisting bottoming on large impacts.
Practical Example
If you are a street rider weighing 90kg with gear on a bike with a 2.4 leverage ratio, the calculator might suggest a 95 N/mm spring. If you frequently carry a 70kg passenger, you should step up to a significantly stiffer rate, or adjust your preload, though a spring change is the better long-term solution for handling geometry.