Author Topic: gc coils, spring rate (Read 4169 times)

E30choa · « **on:** December 13, 2009, 09:51:28 PM »

so i have ground control coils, with spring rates,375 in the front and 450 in the rear with blistien sport shocks, but the front is more stiffer, shouldnt the rear be more stiff ? or is it just the weight of the car? or maybe the springs are opposite:confused:

a little help thanks...

gtatbrissy · « **Reply #1 on:** December 14, 2009, 02:13:41 AM »

usually u have a stiffer spring rates in the front because you have a big heavy engine pushing down on the front

dwtaylorpdx · « **Reply #2 on:** December 14, 2009, 02:15:31 AM »

The numbers are printed on the coils in white paint as I recall so you should be able to check without pulling them, might need a mirror.

The rear has leverage advantage over the spring, the front does not so its effective spring rate with the leverage from the trailing arm is likely around 300 in the rear, you'd have to measure the angles, and lengths etc and calculate the movement ratio. (Unless some smart duck on here knows the motion ratio of the springs on a E30 ?)

Dave

1991 E30 M42 · « **Reply #3 on:** December 14, 2009, 11:05:01 AM »

Quote from: dwtaylorpdx;82989

The numbers are printed on the coils in white paint as I recall so you should be able to check without pulling them, might need a mirror.

The rear has leverage advantage over the spring, the front does not so its effective spring rate with the leverage from the trailing arm is likely around 300 in the rear, you'd have to measure the angles, and lengths etc and calculate the movement ratio. (Unless some smart duck on here knows the motion ratio of the springs on a E30 ?)

Dave

what he said, I do not know the ratio but I will probably know soon as I intend on replicating our suspension in suspension analyzer.

White325is · « **Reply #4 on:** December 14, 2009, 11:22:45 AM »

For an E30 you want stiffer spring rates in the rear.
If you want stockish ride with coulds get 400 front 500 rear. If you want something a little stiffer get 550 front 650 rear. On my daily I run 650/750....

E30choa · « **Reply #5 on:** December 14, 2009, 12:14:19 PM »

yeah ill be checking the springs making sure there on there correctly, and yeah i rather have the rear stiffer then the front forsure

1991 E30 M42 · « **Reply #6 on:** December 14, 2009, 02:00:35 PM »

when you say you want the rear stiffer, do you mean actual spring rate, or effective spring rate, if your effective rate in the rear is stiffer than the front, you will have a drift car

flyinglizard · « **Reply #7 on:** January 29, 2010, 08:28:34 AM »

Front wheel rate is about 95% of spring rate.
Rear wheel rate is about 55- 60% of spring rate. for the E30.
Just measure how much the spring attatchment point moves, RE to the contact patch of the tire.

dvmotorsports · « **Reply #8 on:** January 29, 2010, 11:22:23 AM »

I'll catch shit for this but....

Spring rate is meaningless as it is totally modified by two things: the sprung weight of the vehicle and the leverage exerted by the suspension.

:flamesuit: