Join Date: Feb 2009
Location: Largo, FL 33774
I have lowered my car, and there are a few things you have to consider. If you are going to just put lowering springs on the car, it is relatively easy. The only major issues will be tire clearance, camber on the front, and springs falling out at the rear. If you are going to use drop spindles in the front, you should have the front end aligned, but you will not have to make the camber adjustment for the spring lowering. You will have to check for tire clearance because the drop spindles move your wheel out about 1/3 to 1/2 inch.
Front tire clearance is only a problem if you get wide tires. A 27 inch 255 tire (same as a stock Imp tire) will not give you any problems until you get really low (2 1/2-3 inch from stock Caprice height). Rears are a little more forgiving in width up to 275. You can stagger the rims and it will not hurt anything as long as the rims have the original offset. I believe it is -6mm. The distance from the outside of the backside of the rim to the contact surface should be about 1/2 inch more than 1/2 of the width of the rim. For example a 9 inch wide rim would have an offset of 5 inches (9" divided by 2 +1/2") from the back of the rim
You will have negative camber in the front when you lower it with springs. Measure the front axle center line (take the dust cap off) to the bottom of the fender vertically before you do anything, and write it down. Once you have lowered it with springs, measure it again to find the drop (you have the drop without tire variables). You have to remove 0.030 in shim thickness from all alignment stacks for each 1/2 inch of drop to correct for the negative camber. If you do not, it will wear the insides of your tires excessively, and quickly. For example, if you drop it 2 inches that will require the removal of 0.120 of shim thickness.
The rear springs from most manufacturers are shorter than the OEM springs. If you do not put a drop shock (short) on the rear, when you jack the car to change tires, the springs will fall out, because they do not touch the top spring perch when the suspensions drops. You can use your original shocks if you have a 3-4 inch piece of exhaust pipe welded to the center of the top perch. It keeps the spring aligned so that it lands on the spring perch when you lower the car again. You should also consider using a tiewrap to hold the spring on the axle perch to keep it from slipping off when the car is jacked.
Mechanically you will not hurt the car by dropping it. Depending on who many miles are on the front components, and while you have it apart, you might consider new bushings and ball joints just to replace any unknown worn out parts, and give it a fresh feeling suspension. You can buy complete new arms with BJs and bushings from Rock Auto for less than having yours rebuilt, unless you are using upgraded aftermarket wear parts. Always tighten the bushing bolts when the car has full weight on the suspension to avoid stress on them which would shorten their life substantially. Because of the limited access to the underside after lowering, you may have to have it on a rack to tighten them. While I had my car on jackstands with the wheels off, I jacked up the respective arm until the frame lifted off of a jackstand then tightened the bolts. The rear is similar to the front for the bushings, but you do not have completely separate action for each side. I would also update wear parts for the drop spindles as well.
1991 OCC 461 (.030 over 454) BBC, 3.23 posi, flash to pass, drop spindles & springs, Impala rims, Hydroboost, Recaros, MOMO/wood SW w/QR, custom wood shift knob, Pioneer DEH P77DH
1992 OCC now with 5.7 tbi, DEH P77DH
For a parts list, check https://www.impalassforum.com/vBulle...ion-parts.html