NSX

hey guys,
i was reading that article that bbarbulo posted about the basics of suspension and i learned a bit. but my question is that i thought that load transfer on the tires induce the understeer/oversteer on the car. and i know for a fact that load transfer happens because of the couple produced by the distance between the cg and roll center of the car. now if that is so where does increasing/decreasing the spring rate come in to induce understeer/oversteer. this has been troubling me for a while now hehe, ive asked many ppl but they always tell me to never use spring rates to balance my car and its only to be used to reduce roll. i would really appreciate for ur input guys.

imported_gatherer

I confused by your question... prime example of load transfer is body roll in a turn

stieer springs reduce roll at that side (so if you stiffenthe front only it'll roll less then the back)

now common knowledge is that stiffer rear = more oversteer

Stiffer front = more understeer

now why does making it stiffer affect this you';d think stiffer = less body roll (and it does... ) but doesn't that mean less weight transfer? nope

with less body roll there is more wieght transfer ... witht he soft stock suspension there is alot of body roll body roll is motion and reduces weight transfer. (hard Idea to grasp but it';s important)

now with the rear suspension when you have stiffer sprinsg back tehre you are loading up the outside tire more with the wieght transfer this causes the tire to go over the optimal wieght for grip and therefore reduces grip this results in a reduction of traction. if you reduce traction int he rear you get oversteer. (note I'm not saying that traction is reduced to nothing)

now for the front same thing happens when you go stiffer except that loss of traction causes understeer...

I hope this helps ... maybe I've just confused you more

NSX

thanks for ur reply man and sorry for the confusing question,
but the thing is im reading this book by caroll smith and he said that springs only reduce roll and they dont contribute to load transfer which in turn induces understeer/oversteer. he just said that the further above ur cg is from the roll center axis of ur car, the more load is gonna be transferred (sort of like a moment arm where u have a load on a stick and the longer the stick, the more force its gonna produce)

i use to believe what u said about that load is transferred quicker to the outside tire with stiffer springs and thats y it puts too much load on the tire and slips.

but right now i still dont know which is right.

do know of any way for me to test which theory is actually correct? and thanks again

imported_gatherer

Carroll Smith is generally correct... no way I'm arguing with that mind....

but if thats the case then why do most Front wheel drive race cars use super stiff springs on the rear and softer ones on the front? THeory is one thing Practice is another....

bbarbulo

iTrader: (2)

I don't feel like reading so much, but I think I got the jist of your question....

basically it's very simple.

stiffer springs prevent weight transfer to the corner of the car where the stiffer spring is installed. agree?

so if there is less weight transferred to that corner, it will have less weight on the tires? yes? so if there is less weight on the tires, there is less traction on that side. less traction means more likely to break away.

so let's review. stiffer springs all around (same % increase) reduce roll but leave the attitude of the car the same.

altering spring rates so that the rear is stiffer (increase stiffness in the rear more than the front) causes less weight transfer to the rear, therefore causing less traction to the rear. now, this isn't a universal truth, it's more of a guideline.

say for example you are halfway through a turn and your rear end starts to let go. naturally being a good driver you mash the throttle to attempt to rebalance the car by transfering weight to the rear (acceleration transfers weight backwards). if you have stiff springs in the rear, the car will resist your attempt to rebalance and may continue the skid. this is the reason most cars come from the factory set up to favour understeer rather than oversteer.

peoples natural tendency to mash your brakes in any sort of situation favours oversteer, so to be on the safe side, manufacturers have set up most cars to favour understeer.

so there is no need to worry about altering spring rates in diff't proportions as long as you keep that in mind when you drive at the limit. it would be good to test out your new limits in a safe environment.

StewPiddass

Like solo2... that's where Gatherer and I test our higher rear spring rates every weekend!


Now if I was building a street car, or even a track car, I'm not sure I'd go with higher rates in the rear. But because our cars are prepped for solo2 we need lots of rotation therefore the stiffer rear rates. I personally run 400fr and 500rr, I forget what Gatherer runs but I believe his difference is even more aggressive than mine.

NSX

ah, that makes sense too but how come gatherer said the opposite hahaha

"now why does making it stiffer affect this you';d think stiffer = less body roll (and it does... ) but doesn't that mean less weight transfer? nope

with less body roll there is more wieght transfer ... witht he soft stock suspension there is alot of body roll body roll is motion and reduces weight transfer. (hard Idea to grasp but it';s important)"

the way i think of it is that spring rates is the rate of load transfer to the tires. so the higher the rate (stiffer) the faster the load is gonna be transmitted to the tires and that causes the tires to slip. but the only fact i know is that springs do not promote weight transfer. but then i can be all wrong, thats y im askin u guys since u have had more experience with this stuff than me hehe. ne ways ill keep searchin