K Tech Suspension Spring Rate Calculator

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K-Tech Spring Rate Calculator

kg lbs
Sportbike / Supersport (600-1000cc) Adventure / Touring Motocross / Enduro Naked / Street Standard
Street / Commuting Fast Road / Canyon Track Day / Racing

Recommended K-Tech Spring Rates

Front Fork Spring Rate:
Rear Shock Spring Rate:

Note: Values are calculated in N/mm (Newtons per millimeter), the standard unit for K-Tech performance springs.

Understanding Suspension Spring Rates

Choosing the correct K-Tech spring rate is the single most important modification you can make to your motorcycle's handling. Spring rate refers to the amount of force required to compress a spring by a specific distance. K-Tech springs are manufactured from high-tensile chrome silicone wire and are designed to provide consistent performance under extreme conditions.

Why Spring Rate Matters

If your springs are too soft for your weight, the bike will sit too low in its travel (oversag), leading to harsh bottoming out and poor steering geometry. If they are too stiff, the suspension won't move enough to absorb bumps, resulting in a loss of traction and rider fatigue. Correct spring rates ensure your suspension operates in the "sweet spot" of its stroke.

The Front vs. Rear Balance

Front fork springs typically range from 8.0 N/mm to 11.0 N/mm for sportbikes. Rear shock springs are much stiffer due to the linkage leverage ratios, often ranging from 80 N/mm to 120 N/mm. Our calculator accounts for these differences based on your specific bike category and weight.

Example Calculation

A typical 85kg rider on a 1000cc Sportbike used for track days would generally require:

  • Front: 9.5 N/mm to 10.0 N/mm
  • Rear: 95 N/mm to 105 N/mm

Always verify your static and rider sag measurements after installing new K-Tech springs to confirm the rates are perfect for your chassis setup.

function calculateKTechRate() { var rawWeight = parseFloat(document.getElementById('riderWeight').value); var unit = document.getElementById('weightUnit').value; var bikeType = document.getElementById('bikeType').value; var style = document.getElementById('ridingStyle').value; if (isNaN(rawWeight) || rawWeight <= 0) { alert("Please enter a valid weight."); return; } // Convert all to KG for internal logic var weightKg = (unit === 'lbs') ? rawWeight * 0.453592 : rawWeight; var baseFront = 0; var baseRear = 0; var weightFactorFront = 0; var weightFactorRear = 0; // Set baseline logic based on bike type if (bikeType === 'sport') { baseFront = 9.0; baseRear = 90; weightFactorFront = 0.035; weightFactorRear = 0.4; } else if (bikeType === 'adventure') { baseFront = 6.5; baseRear = 120; // Adventure bikes often have high linkage ratios weightFactorFront = 0.025; weightFactorRear = 0.6; } else if (bikeType === 'mx') { baseFront = 4.4; // MX units are usually lower baseRear = 52; weightFactorFront = 0.015; weightFactorRear = 0.2; } else { // Naked/Street baseFront = 8.5; baseRear = 85; weightFactorFront = 0.03; weightFactorRear = 0.35; } // Adjust for Rider Weight relative to 75kg (standard test rider weight) var weightDiff = weightKg – 75; var finalFront = baseFront + (weightDiff * weightFactorFront); var finalRear = baseRear + (weightDiff * weightFactorRear); // Adjust for Riding Style if (style === 'spirited') { finalFront += 0.25; finalRear += 2.5; } else if (style === 'track') { finalFront += 0.75; finalRear += 7.5; } else { finalFront -= 0.25; finalRear -= 2.5; } // Round to nearest common K-Tech sizes (usually 0.5 increments for front, 5.0 for rear) finalFront = Math.round(finalFront * 2) / 2; finalRear = Math.round(finalRear / 5) * 5; // Min caps if (finalFront < 3.0) finalFront = 3.0; if (finalRear < 30) finalRear = 30; document.getElementById('frontRate').innerText = finalFront.toFixed(1) + " N/mm"; document.getElementById('rearRate').innerText = finalRear.toFixed(0) + " N/mm"; document.getElementById('ktechResult').style.display = 'block'; }

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