вот чего нашел,
есть даже и физическое обоснование
"I bought some spring clamps for $3.99 a pair. When you shorten springs, it has a twofold effect. You lower the vehicle's center of gravity (good for handling), and you stiffen up the spring rate (good for handling). Merely shortening the spring actually changes the spring rate.
Imagine a 10 coil spring sitting upright on a table. You place 200 lbs on the spring. The weight moves the top of the spring down 1 inch. So your spring rate is 200 lbs per inch. Each one of the ten coils has shrunk 1/10 of an inch.
Now cut the spring in half. You have 5 coils now. When you place the 200 lbs on it, each coil still shrinks 1/10 of an inch. (same diameter coil, same amount of deflection.) Because there's only 5 coils, the spring will only move down 5/10 of an inch.
This gives you a new spring rate of 400 lbs per inch. Twice as short = twice as stiff.
Say there's 6 coils on your springs. You can stiffen them up by 1/6 , if you cut off one coil. Clamping two coils together is very similar to cutting off a coil. Cheap and effective; you get the same two-fold benefits.
So instead of buying stiff expensive "sport" springs for my Acclaim, I clamped two coils together on all four wheels. There was a MAJOR improvement in the Acclaim's handling, once lowered & stiffened. Then I put a little negative camber in the front wheels, and got rid of the factory's toe-in.
After driving around corners like a bat out of hell, there was no need to buy new sway bars! You can ask the owner of the new Corvette that I wasted on the Cross Bronx Expressway (very twisty) on the way home from Atco's ID Drag Wars 3 weeks ago, after blowing away a twin turbo Supra at the track. (the standing ovation from over a thousand people sent chills up my spine; what a hoot!)
The bolts that come with these clamps do not break! Don'y worry over nothing. My car weighed 3,000 lbs when I put them on, and my van weighed 3,250 lbs when I put them on. They're good on any sized vehicle. If you use one clamp per spring, it lowers & stiffens exactly like cutting off half a coil. If you put 2 clamps on the same coils, almost opposite each other, you get the effect of cutting a full coil. By sliding the coils closer together and farther apart, you have a "tunable" spring rate, and adjustable vehicle height. "
(c)
http://www.allpar.com