Touring cars

[johnny99]

I'm looking for info on roll centre's, bar and spring rate's etc on modern touring cars. I am currently running an Lancer Evo 4 and an Impreza Sti in the Irish Time Attack series and doing very well. Both cars are lowered by about 60mm and of coarse the distance from the roll centre to the CoG will have increased. I have raised the roll centre (decrease the distance from RC to the CoG) on the front only by a little. Am I correct in thinking that the RC should be higher on a Saloon car with very little aero, than a single seater with good aero. Is the a Forum as good as this one that covers modern touring cars. I am looking for this info as, for next season I am building a Saloon (FWD),

John

[Belatti]

Johnny,

a nice discussion about CoG and Roll centers in this thread:

viewtopic.php?f=6&t=6834&start=30

its still lacks some explanations for the common mortals (me included) but its at least interesting.

About spring rates, I know some 350HP RWD 1300Kg touring cars here are designed at arround 3Hz front and 2Hz rear. Thats natural frequency to the wheel (no tire included) with installation ratios very close to 1 and with the least variation with camber angle.

[johnny99]

Yes, most of the info availible is single seaters with aero. The CoG is very low and the RC is below the ground. This is different to a saloon car where the RC and CoG is higher. When a saloon car is lowered the CoG is lowered, but the distance between both increases, which, if the body won't roll, the car will lift the inner wheel.

John

[mep]

Give me a try...

When you lower your car your roll center might also change a bit
but the effect will be really small.

Roll Centre's position is a compromise between roll moment and jacking force.
When your car goes through a corner with a RC above ground level, you will get a force from the suspension lifting the car up (jacking force-which is negative for handling).
When your RC is below ground you have a negative jacking force (positive for handling) but then you have a huge distance between RC and centre of gravity which gives you a big roll moment (negative for handling).
But I guess you know the stuff that far.