Dirt Bike Spring Rate Calculator
Dial in your suspension for better traction and control
Recommended Setup:
Fork Spring Rate
kg/mm
Shock Spring Rate
kg/mm
Note: These are estimated starting points. Always verify with proper sag measurements.
The Ultimate Guide to Dirt Bike Spring Rates
Setting the correct spring rate is the single most important modification you can make to your dirt bike. Suspension shops often say that "valving is for comfort, but springs are for weight." If your springs are too soft or too stiff for your body weight, no amount of clicker adjustment will make the bike handle correctly.
Why Spring Rate Matters
Your springs support the combined weight of the bike and rider. If the spring rate (the amount of force required to compress the spring a specific distance) is incorrect, the bike will sit too low or too high in its stroke.
- Too Soft: The bike dives under braking, bottoms out on jumps, and feels "mushy." This often causes the bike to feel harsh because you are riding in the stiffest part of the internal valving.
- Too Stiff: The bike lacks traction, deflects off small rocks/roots, and feels like a pogo stick. It prevents the suspension from using its full travel.
Understanding Sag Measurements
To verify if your calculated spring rate is correct, you must measure Race Sag and Static Sag:
| Sag Type | Recommended Range (Full Size Bike) |
|---|---|
| Race Sag (Rider on bike) | 100mm – 105mm |
| Static Sag (Bike weight only) | 30mm – 45mm |
If you set your Race Sag to 105mm and your Static Sag is less than 30mm, your spring is too soft. If your Static Sag is more than 45mm, your spring is too stiff.
How This Calculator Works
Our algorithm uses base rates for common displacement classes (85cc, 250cc, 450cc) and applies a linear adjustment based on the deviation from the "standard" 175lb rider. It also applies multipliers for riding style—Enduro riders typically prefer 1-2 rates softer for technical compliance, while Desert riders need stiffer setups to handle high-speed G-outs.