Suspension Coil Compressors
Note: Allpar does not endorse and cannot take responsibility for any of these modifications.
Gus Mahon wrote:
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.
Installation of coil spring compressors
After you jack up the wheel to compress the spring, then you take a large pair of Channel Lock pliers, and compress the 2 center coils a little more. Then they fit. After the installation, hacksaw off the protruding bolt ends.
harber wrote: You don't have to remove the tire or the spring. In the case of the front springs (at least on the last car I did) I had to compress the spring, it was easy though, I just used a floor jack to raise the car by its A-frame.
harber agreed: Those things are a piece of cake. I had a set on a car of mine a LONG time ago and they did work. They are essentially a U bolt with a clamp at the bottom side. The U bolt slips over the spring, then a slip-on clamp goes on the bottom spring, then you tighten two nuts to compress the spring. Easy. ...
Brain P. Minnebo agreed: I was going to mention Gus's $4 per spring upgrade. It is the ultimate bang-for-the-buck (b4b?) way to turn your stock springs into perfomance parts.
...but Bradley Miller wrote:
As for the lowering -- just changing tires can make a killer effect on the car. I went from 195-60HR15 to 195-50 and got immensely different handling from my old 2.5L Duster. The tires are the biggest key to making anything work -- too much sidewall deflection, and suddenly your squirming around on an inch of tread on the sidewall. Between that and a decent alignment, you'd be surprised what can be done.
Try the welded up rear axle -- it consists of basically boxing that U channel that forms the rear axle. This keeps the rear end from flexing. Be sure to stitch weld -- alternating to keep from warping the axle. Ed Peters said he has a jig to do those axles all at one time -- but just taking your time you can do it while on the car. (Make sure the car is level and loaded equally!)
...and Mike Swern wrote:
For MacPherson strut suspensions, it is generally not a good idea to lower more than .5-1.5 inches. After that, bump steer is greatly increased. The advantage of sport springs over [clamps] is that the spring rate is higher on a sport spring and many sport springs are progressive rather than linear. Yes, the spring ratio is raised when you use the clamps. but if you live near the city (read potholes) then your may want to consider sport springs. Lowered springs don't have as high a rate and can hit the bump stops under maximum load. for most of us, that shouldn't be a problem.
Again, if you live near potholes, though, especially with a more aggressive wheel combination like 50 or 40 series tires, be prepared to shell out some dough for new rims if you hit your bump stops in a pothole. Also, progressive springs give a nicer ride while keeping good handling characteristics because they soak up the small bumps while hardening up for the twisties.
Does the spring rate really change?
Drew wrote -
The information given by Gus Mahon regarding shortening a spring to increase its stiffness is incorrect. A standard spring (non-variable spring rate) has a single stiffness (spring rate) no matter its length. A spring with a 200lb/in spring rate will deflect 1" under a 200lb load no matter how long it is (given it is long enough to deflect 1". Therefore shortening it would not make it stiffer, just limits its maximum possible deflection. There are only two ways to increase the spring rate: 1) Purchase a new spring with an increased spring rate or 2) Install two springs in parallel. The new spring rate (Keq) would equal K1 + K2, where K1 and K2 are the initial springs rates of the two springs. The only benefit of chopping or compressing the coils are the reduced center of gravity.
Bob Sheaves answered -
Specifically, there are portions of both claims that are true. A spring designed for 200lb/in and a certain length is a certain wire diameter. When you "shorten" the spring by some amount and NOT changing the wire gage diameter the rate goes up becasue the rate is a function of the diameter of the wire times its length (if uncoiled).
Basically, think of the coil spring as a long torsion bar. Keep the diameter the same and shorten the bar and it gets stiffer (more resistant to twisting efforts). Keep the length the same and increase the bar diameter and it also gets stiffer. A coil spring is a "dual axis" torsion bar, in rough terms—a mandrel centerline, and a wire gage centerline.
