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This calculator is frequency based and operates in a different way to every other spring calculator. It has been configured to work well for most XC through Enduro bikes in the 120-180 mm travel range. It has not been verified on DH bikes yet. That work is still in progress.
Sag numbers are based on the rider in the attack position. Sag is difficult to measure, is affected by dozens of other variables and doesn't really matter unless your numbers are out enough to affect geometry and bike handling.
You must purchase a voucher code to use this calculator. The voucher code will be emailed to you after purchase and can only be used once. Simply click add to cart and proceed through the checkout process to purchase a voucher code. Your results (rear shock spring rate & sag approximation) will be emailed to you.
If you want spring rates for both your fork and rear shock use our Bike Spring Rate Calculator - Advanced - Front & Rear Spring.
Unsprung Front & Rear (kg)
Unsprung Front is the weight of your complete front wheel plus allowance for brake & fork lowers. For lightweight bikes it is usually ~2.5 kg, for heavy weight bikes it is usually ~3.5 kg.
Unsprung Rear is the weight of your complete rear wheel plus allowance for suspension linkages, brake & drive train. For lightweight bikes it is usually ~3.5 kg, for heavy weight bikes it is usually ~4.5 kg.
Accuracy for this is not super critical so an estimate of the fork, brakes and suspension linkages is okay.
IFP Preload
IFP preload or force is the shaft force your rear shock presents due to the internal gas charge. It can greatly change sag numbers but has little effect on spring rate.
Pick the best example:
Cane Creek DB Coil 8 mm shaft = 5 kg
Fox DHX2 9 mm shaft = 7 kg
Fox vanilla Old School 3/8" shaft = 10 kg
RS Super Deluxe Coil 12 mm shaft = 16 kg
Manitou Swinger/Revox 18 kg
Fox DHX/Vanilla with 1/2" shaft = 18 kg
Marzocchi Bomber CR with 1/2" shaft = 18 kg
Fox DHX/Vanilla with 5/8" shaft = 27 kg force.
Enter details and click submit for the results to be emailed to you.
SKU:CALC-BIKESPRINGRATEADV
SKU:CALC-BIKESPRINGRATESIMP
SKU:CALC-COILSPRINGSIMP
SKU:CALC-COILSPRINGDET
SKU:CALC-SPRINGRATECONVERT
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