Use the spring rate estimator below to decide if the RFY spring package will provide a working setup for you. If approximate sag is less than .5 of an inch it is too stiff. If the sag is greater than 2 inches, the spring is too soft.


Enter your weight, your bike’s weight, and pick a spring from the drop down. The form will calculate the rest.

Calculation Formula

This equation assumes that your bike has a 50/50 front to rear weight distribution.

(Bike Weight) * (.15)  = Unsprung Weight

(Riders weight) + (Bikes Weight) – (Unsprung Weight) = Total Sprung Weight

(Total Sprung Weight) / (2) = Load on Rear Suspension

(Spring Rate) * (2) = Total Rear Spring Rate

(Load on Rear Suspension) – (Total Rear Spring Rate) = Weight Differential

(Load On Rear Suspension) / (Total Rear Spring Rate) = Approximate Sag

(Weight Differential) / (Spring Rate) = Approximate Sag with One Inch of Preload

Warning and Caveats

Given that this calculation assumes a 50/50 weight distribution this calculator may not accurately reflect your bikes characteristics.

Rear suspension geometry dictates there is a ratio between movement at the wheel versus that of the spring. This motion ratio is assumed to be 1/1. As a result the calculations produced here may not accurately reflect your bikes properties.

This calculator is meant to give a simple understanding of the available spring rates in relation to your bike and weight. It should NOT be considered a decisive tool.

This calculator has been updated to consider unsprung weight. It uses a standard rate of 15% total unsprung weight for its calculation. This number is an estimate at best. Previous iterations of this estimation tool made no concessions for unsprung weight, thusly it was decided that even a rough estimate for unsprung weight would be better than not considering it at all.