K-Tech Spring Rate Calculator
Street / Commuting
Sport / Fast Road
Race / Track Day
Motocross / Off-Road
Front Fork Springs (Pair)
Rear Shock Spring (Single)
Lightweight (Under 400cc)
Middleweight (600cc – 750cc)
Heavyweight (1000cc+)
Recommended K-Tech Specification:
Estimated Spring Rate: N/mm
Understanding Suspension Spring Rates for K-Tech Performance
Choosing the correct spring rate is the single most important step in setting up your motorcycle's suspension. Whether you are installing K-Tech 20IDS cartridges or a 35DDS Pro rear shock, the hardware can only perform if the spring rate matches the rider's weight and the bike's mass.
What is Spring Rate (N/mm)?
The spring rate refers to the amount of force required to compress a spring by a specific distance. K-Tech springs are measured in Newtons per millimeter (N/mm). A 9.5 N/mm fork spring requires 9.5 Newtons of force to compress it 1 millimeter. If your spring is too soft, the suspension will ride too low in the stroke (blowing through travel); if it is too stiff, the bike will feel harsh and lose mechanical grip.
How to Choose Your Rate
When using a spring rate calculator, we look at several critical factors:
- Rider Weight: This must include your full riding gear (helmet, leathers, boots, gloves), which typically adds 7-10kg.
- Application: Track riders require stiffer rates to handle high-speed braking loads, whereas street riders benefit from slightly softer rates for compliance over potholes.
- Linkage Ratio: Rear shock rates vary wildly between bikes because of the mechanical advantage provided by the rear linkage.
Typical Examples
For a standard middleweight sportbike (e.g., Yamaha R6) with an 85kg rider:
- Road Use: Fork springs approx. 9.0 N/mm | Shock spring approx. 95 N/mm.
- Track Use: Fork springs approx. 9.5 – 10.0 N/mm | Shock spring approx. 100 – 105 N/mm.
Always verify the static and rider sag after installation to ensure the calculated rate is achieving the correct geometry for your specific motorcycle model.