Torsion bars
Posts 11 and 13 are dead wrong. Dead wrong.
Evidently they have never scaled a torsion bar car, use preload or understand spring rates.
The lighter the spring rate, the more compressed height (think coil spring since it's easier to visualize) there has to be to hold the car at the same height.
Let's consider an example that is easy math.
You have two springs. Spring one has a rate of 100 pounds per inch, and spring two is 500 pounds per inch. Extreme numbers but it makes easy math.
The 100 pound spring will be to be compressed down to a length of 10 inches to get 1000 pounds of spring load and hold the car at ride height. Let's say the spring has a free height 20 inches. That means it has an installed height of 10 inches.
The 500 pound spring will need to get the same 1000 pounds of spring load. To do that the spring is only 15 inches long in free height, and installs at 13 inches as it takes only 2 inches of spring compression to get the same ride height as the 100 pound spring.
No matter what you do, considering shock settings are the same, the 100 pound spring will have more stored energy. So...that means when you mash the throttle and weight transfer begins, for every inch of front end travel in the extension direction will only require removing 100 pounds for every inch of spring travel. The 500 pound spring will require removing 500 pounds to make the spring extend just one inch.
It's simple math.
It is simple math, but you got the physics wrong.
First, your example is clearly for a coil spring set up. Free height and installed height are totally meaningless on a torsion bar suspension, and that matters because unlike a coil spring set up you can't realistically preload the torsion bar. If the UCA isn't pinned to the upper bump stop then the weight of the car is the amount of stored energy. If you change the corner weights on a torsion bar car you're changing the height in the front.
Second, there is
no difference in stored energy, not even in your example. The 100 lb spring compressed 10 inches and the 500 lb spring compressed 2 inches have EXACTLY the same amount of stored energy, 1000 lbs. They have different compressed heights, but the same exact stored energy.
So, why do drag racers want light springs? Well it has
nothing to do with stored energy. It's about weight transfer. Which is about traction. To go back to the part of your example that you got right, when you mash the throttle you start weight transfer because of acceleration. And the car with 100 lb springs will rise 1" for every 100 lbs worth of transfer you get due to acceleration. With a 500 lb spring you only get .2" of rise for that 100 lbs of transfer. That means that the car with 100 lb springs will be higher in the front, which moves the center of gravity of the car further back, so, more weight on the rear wheels. Which means more traction.
But please note, the same amount of energy was released from the spring. The difference is the change in front end height and the additional weight transfer that occurs because of that change in height moving the CG, not a difference in the stored energy of the spring. The 1" rise in the 100 lb spring and the .2" rise in the 500 lb spring release the same 100 lbs of energy stored in the springs.
