A car's natural frequency (in Hz) is the number of times a car will bounce up and down each second. Typically, a family sedan will have a spring frequency of around 1hz, a sports car around 1.5hz, and a race car around 2hz.

Overall:

Vehicle Weight with Driver:

3500

lbs

Front axle weight:

2030.00

lb

Wheelbase

100

in

Rear axle weight:

1470.00

lb

Weight per front spring:

920.00

lb

Weight per rear spring:

645.00

lb

Front:

However, it is commonly taught to run a spring frequency higher in the rear than the front. The idea is to have the oscillation of the front suspension finish at the same time as the rear. Since the delay between when the front suspension hits a bump and the rear suspsension hits that bump varies according to vehicle speed, the spring frequency increase in the rear also varies according to what speed the one wants to optimize for. This calculator will calculate your rear spring rate for you based on your selection of front spring rate.

Weight Distribution:

58.0%

Front wheel rate:

210.76

lb/in

Motion Ratio (see worksheet):

0.97

Droop travel to unload spring:

4.13

in

Unsprung Weight:

95

lbs/side

Damper rates at Optimal Damping:

129.64

N/mm/sec

Spring rate:

224

lbs/in

Front natural freq:

1.50

Hz

Rear:

Weight Distribution:

42.0%

Rear wheel rate:

186.32

lb/in

Motion Ratio (see worksheet):

0.98

Droop travel to unload spring:

3.19

in

Unsprung Weight:

90

lbs/side

Damper rates at Optimal Damping:

102.06

N/mm/sec

Spring rate:

194

lbs/in

Rear natural freq:

1.68

Hz

Recommended rear spring rate:

Optimize for this speed:

80

mph

Recommended rear wheel rate:

185.03

lb/in

Recommended rear natural freq:

1.68

Hz

by Steve Edwards

Recommended rear spring rate:

192.66

lb/in

Damper Rate Calculator

Compare your shock dyno by plotting your values here:

Optimal damping ratio:

65%

critically damped

Velocity (mm/s):

0

50

100

150

200

Rebound Force (N), Front:

0

200

550

800

1000

Rebound Force (N), Rear:

0

100

300

550

700

Within 65-70% critically damped is said to be the ideal damper setting for both handling and comfort simultaneously. Most modern dampers show some digression to them as well, meaning they may be 70% critically damped at low piston speeds but move towards 40% critically damped at high piston speeds to allow the absorption of large bumps. Damping is most important below 100mm/second as this is where car control tuning takes place. This graph shows rebound resistance only; bump resistance should be no lower than one third of rebound resistance.