This is the way I see it.....
You mash the pedal and unleash all your torque on the rear tyres. A stiff spring allows no give at all and makes it harder for the tyre to get traction, a softer spring takes that shock and slows it down, making it easier for the tyres. Think of your tyre as a fishing line and the fish as your engine power. See how some guys can land a 20lb fish on 2lb line when other guys can't land a 1lb fish on 2lb line. The fish weighs the same, just the application of force is different.
This does not take into consideration weight transfer. To make it easier for your rear tyres it helps to put more weight on them. 90/10s and long soft front springs will throw some of the front mass onto the rear wheels. This makes it easier to get traction.
In a perfect world the best vehicle reaction time comes with no suspension - look at a dragster. The sad reality of a street car is you need bandaid fixes like springs and shocks to counter the weight distribution and lack of tyre.
If you want to run firm springs and shocks and go drag racing you can, you just need a huge tyre to get the traction you need. In fact, as stated earlier the stiffer the suspension, the quicker the car will react, but in reality the shock on the tyres will be too much and they will likely go up in smoke.
This is just a basic look at what happens, other factors such as HP and TQ and the force the tailshaft exerts on the diff housing (causing the left or pass. side of the car to lift, and the right or drivers side to dip) make getting a torquey street car to leave efficiently quite a challenge. There are many street cars in the 8-11 sec bracket with different shock/spring combos on each corner.
P.S. A soft spring does NOT increase down force. It just softens the shock on the tyre. The force is the same, it just gets applied differently. Bear in mind also, the drivers rear wheel is trying to LIFT upon acceleration. A soft spring on this corner will not help traction. This is why an auto car when linelocked spins the drivers rear wheel. The weight is coming off it and being applied to the pass. side wheel. The drivers side tyre gets lighter and spins easier. The pass. side wheel is pushed so hard into the road that that side of the car is lifted.
Edited by Struggler, 10 February 2006 - 07:01 AM.