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Suspension & Setup

Suspension Spring Rate Calculator

Estimate fork and shock spring rates from rider weight, sag targets, and linkage leverage. A starting point for ordering springs — not a replacement for a tuner.

Inputs

Wet weight is fine

Wheel travel / shock stroke. MX linkage is often 2.4–3.2

Results
Live

  • Shock spring

    17.89N/mm

  • Shock spring

    102.2lb/in

  • Each fork spring

    3.37N/mm

  • Each fork spring

    19.3lb/in

  • Load on front

    641N

  • Load on rear

    723N

Formula

k = (supported weight × gravity × leverage) / sag

Related calculators

Sag
Sag is how far the bike settles from fully extended. Measure from a fender mark to the axle with the bike on a stand, then on the ground.
Race Sag
Race sag (rider sag) is measured with the rider in full gear, balanced on the pegs. Most MX bikes want about 100–108 mm on ~310 mm travel.
Rider Sag
Front and rear rider sag together. Enter fender-to-axle (or a zip-tie on the fork stanchion) for each end.
Static Sag
Static sag is bike-only, no rider. Too little static sag with correct race sag means the spring is too soft (you used a lot of preload). Too much static sag means the spring is too stiff.