Fronts softer than rear? Why?

[red]

My roommate has 240sx, he recently purchased coilovers and I asked him what the rates were. He told me 8kg/mm in the front and 6kg/mm in the rear.

I was like wtf? why would the fronts be stiffer?

Then I told him e30's have the rear spring rates were stiffer than the fronts.


Why is it that e30's have stiffer rear rates than fronts?

[E30Kaiser]

Most 240sx's use stiffer rears too, usually only real coilovers setups use stiffer front spring rates, IE the Bimmerworld Speed World Challenge car uses stiffer front rates. I don't know anything past that though.

[AndrewBird]

He wants more understeer then oversteer? :weak:

[red]

Oh hmm... I see.

I'm glad this wasn't a ridiculous newb question.

[ditchdigger]

There is a big difference between spring rate and wheel rate. The spring on the rear is inboard and there is more leverage acting on it than in the front.

Even though the spring rates on an E30 are higher in the rear the wheel rates are actually lower.

[BeirBrennerE30]

There is a big difference between spring rate and wheel rate. The spring on the rear is inboard and there is more leverage acting on it than in the front.

Even though the spring rates on an E30 are higher in the rear the wheel rates are actually lower.

ding ding ding. Spring rates of the spring are not what is felt by the wheel. The ratio of the wheel movement to spring compression times the spring rate is what the wheel feels. 240's have a different rear susupension so the wheel rate in the rear is different

[red]

Oh wow, thanks for the response.

I feel all scientific now that I can explain this to him. (after i look up what some of those terms mean)

[PaintPro21]

you'll see that on an e34 where the rear is a coilover, the spring rates won't be higher in the rear. it's really all leverage, and you have to compare apples to apples.

just ask yourself what spring rate you would put on a car that had a significant front or rear weight shift. would you really keep the factory ratio if there is an inbalance?

[Borat]

I think motion ratio is around 0.7 in the rear for an e30. alot of people seem to get caught out by that.