Choosing the Right Spring Rate for Your Weight and Riding Style

Spring rate is the foundation of every suspension setup. No amount of clicker adjustment, revalving, or oil changes can compensate for having the wrong spring installed in your forks or shock. If the spring is wrong, everything else you do is a band-aid.

“Most suspension tuners think they can compensate for bikes that are undersprung with stiffer valving — they do this to avoid having to talk the customer into buying new springs.” — Travis Flateau, TBT Racing

What Is Spring Rate?

Spring rate is measured in kg/mm (kilograms per millimeter) for fork springs and kg/mm or N/mm for shock springs. It describes how much force is required to compress the spring by one unit of distance. A higher number means a stiffer spring.

Stock motorcycles are sprung for an “average” rider — typically 165 pounds, intermediate skill level, standard motocross conditions. If you weigh more, weigh less, ride a different terrain, or ride at a different pace, the stock springs are a compromise.

Fork Spring Rate Guide by Rider Weight

These are general guidelines for conventional coil spring motocross forks. Your exact rate depends on bike model, riding discipline, and skill level. Always consult a suspension professional like TBT Racing for exact recommendations.

110-130 lbs geared up: 0.40-0.42 kg/mm
130-150 lbs: 0.42-0.44 kg/mm
150-170 lbs: 0.44-0.46 kg/mm (often stock on 250s)
170-190 lbs: 0.46-0.48 kg/mm (often stock on 450s)
190-210 lbs: 0.48-0.50 kg/mm
210-230 lbs: 0.50-0.52 kg/mm
230-250+ lbs: 0.52-0.54+ kg/mm

Shock Spring Rates

Shock spring rates vary significantly depending on whether the bike uses a linkage system or a linkage-less design like KTM/Husqvarna PDS.

Linkage bikes (Honda, Yamaha, Kawasaki, Suzuki): Rates are typically in the 4.6-6.0 kg/mm range. Example: a 170-180 lb rider on a Honda CRF450R might use a 5.2-5.4 kg/mm shock spring.
PDS bikes (KTM, Husqvarna, GasGas): Use different rates because there is no linkage ratio. Same rider might use a 42-44 N/mm shock spring on a KTM 450 SX-F.

Two-Stroke Considerations

Two-stroke bikes are significantly lighter than equivalent four-strokes — typically 15-20 pounds less. This means the total system weight (bike plus rider) is lower, and stock springs may be too stiff. A general rule: go one step softer on fork springs compared to the equivalent four-stroke. If you would use 0.46 kg/mm on a 450F at your weight, try 0.44 kg/mm on a 250 two-stroke.

Air Forks vs. Coil Springs

Some modern bikes use air forks (KTM WP XACT, Showa TAC) where air pressure replaces the metal spring. Air forks offer infinitely adjustable spring rate via an air valve on top of the fork. However, they come with trade-offs: more friction, more maintenance required, and inconsistent feel as temperature changes affect air pressure. Many riders — and many TBT Racing locations — offer coil spring conversion kits for air forks as an upgrade.

How to Know if Your Springs Are Wrong

Your sag measurement is the primary diagnostic tool. If you cannot achieve the correct race sag regardless of preload setting, your spring rate is wrong. Other signs include:

Spring too stiff: Bike sits too high, harsh ride over small bumps, loss of traction, arm pump after 10-15 minutes. Static sag will be less than 15-20mm even with correct race sag.
Spring too soft: Bike bottoms out on moderate jumps or bumps, feels mushy, dives excessively under braking. Static sag will exceed 40mm with correct race sag.

The Real-World Case Study

Travis Flateau shared a case where a customer demanded TBT install springs he had already purchased based on an online spring chart. The rider went out and immediately called back — no traction going up hills, terrible handling. When the bike came back, Travis found the rebound was maxed out at 8 clicks, and the spring was too heavy. Because the spring was too stiff, the customer had to reduce preload excessively to set sag, which threw off the entire geometry.

The fix was simple: replace with the correct (lighter) shock spring, open the rebound back up, re-set preload and sag properly. The customer was happy. The lesson: spring rate selection requires expert knowledge of the full system, not just a weight chart.

What MXA Found

When Motocross Action Magazine tested TBT Racing's work on a 2019 Honda CRF250, the stock bike had 0.47 kg/mm fork springs and a 53 kg/mm shock spring — far too stiff for their 130-pound AMA Pro test rider. The stock setup gave the bike a “stinkbug feel” with the rear too high and the front diving.

TBT Racing installed lighter 0.44 kg/mm fork springs and a softer 4.8 kg/mm shock spring. The result: improved balance, better traction, and the rider could finally use the CRF250's great turning characteristics. MXA rated the work highly. The key takeaway: TBT addressed the springs first, then tuned the valving to match.

Bottom Line

Get your springs right first. Everything else — clicker settings, oil height, revalving — is built on top of the correct spring rate. If the foundation is wrong, the house falls down. Talk to a TBT Racing technician before spending money on valving work if you are not sure your springs are correct.