Motion Ratio

Measuring Motion Ratio is surprisingly simple, but take care, this is the most important measurement because it is used several times in out equations. Take measurements on both sides and average the result.

For Shocks Mounted To a Solid Axle:

• Measure the angle the shock leans forwards or backwards
• Measure the angle the shock leans in or out

For All Other Configurations:

• For best results measure to the nearest 1/16”
• Start with the vehicle at ride height
• Droop the wheel ~4” below ride height (measured vertically), record the exact droop
• Measure and record the distance between the shock mounts
• Raise the wheel to ~4” above ride height (measured vertically), record the exact compression
• Measure and record the distance between the shock mounts
• The amount the shock moved between droop and bump divided by the amount you moved the wheel is your motion ratio

UnSprung Weight

Unsprung weight can be measured by removing shocks from the vehicle and weighing the axles, tires, wheel. If the weight can’t be directly measured with scales, we can look it up using our vast collection of data.

Sprung Weight

If the sprung weight can’t be directly measured with scales, try measuring the entire vehicle and subtracting unsprung weight.

For vehicles with existing coilovers and springs perform the measurements in this article.

For OEM vehicles we have had good success using published curb weights.

Total Wheel Travel

Measure shock shaft showing at full droop.

Up Travel

Measure shock shaft is showing at ride height.

Wheel Rate

For coilovers record upper and lower spring rate. (We will calculate these for you if you’re buying coilovers)

Many lift kit coil spring rates are available online, and we have a pretty complete selection as well.

Wheel Rate for leaf spring vehicles

• Measure sprung weight.
• Set the vehicle at ride height on a flat, level surface.
• Perform the following measurements on both sides and take the average.
• Measure vertical distance from leaf spring (at center pin) to chassis.
• Droop suspension without anything limiting it (ideally done without wheels and tires or axles attached).
• Measure the new vertical distance from leaf spring (at center pin) to chassis.
• Wheel rate = (Sprung Weight) / (Droop)

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