My recent experience on lowering by 2K Z51 Coupe might be of interest. Front end was lowered by removing the adjuster bolts and lathe cutting 2 washers off the bushing, leaving one washer and an 1/8" thickness of rubber cushion on the bolts. When reinstalled and bottomed into the spring, the front end dropped 3/4" both sides, with an inner fender lip measurement at 26 1/4". The rear was lowered by replacing the bolts with 6" long ones and leaving 2 threads exposed on new Nylock nuts. The rear dropped a full 2 inches down to 27". As a matter of fact, the drivers side was 1/4" lower before and after, so after making sure the suspension had settled after 2 weeks, I tightened up on this bolt to raise it. Four full turns on a 13 threads per inch bolt raised this corner 1/4". Trying to correlate how much a change in the contact points of the front and rear control arms with how much each end dropped is interesting. Cutting the front bushings measured 1/2" and screwing the bolts in gained another 1/2" for a total of 1", yet the front only
dropped 3/4". In the rear, I figured I increased the spacing with the new bolt by 1 1/2", yet the rear dropped 2 full inches. Hope this will give some guidlines to anyone interested.
Now, for realignment, the shop had a Hunter machine with a "311" on the computer, but said he couldn't use it because the front side spoilers were in the way of the light beams. I let him do it by hand. First of all, they almost didn't get the car on the rack because the machine has 2 cross beam lifts that the center spoiler would hit. Fortunately, we was able to rotate these as he cleared the beems. After measuring with a bubble device hand held to each rim, he had to significantly adjust the front a lot while the rear was OK. I guess this shows how sensitive the front alignment is to lowereing compared to the rear. I almost had a stroke when I saw him lifting the front and rear ends with the cross beam lifts. He was right under the fiberglass springs. I checked the rear closely, and there was no contact. The front spring is protected by the lower wishbones. I'm sure this is the first C5 this guy did, so when anybody else needs an alignment, they might want to check out the shop's experience first.

 

FYI - in the future, these are EASILY (2 or 3 bolts) removed.

-Jim

 

I lowered mine an inch and a half all the way around.Did not feel alignment was necessary... that was 2 years and 35000 miles ago...I still have 3/32 of rubber on my original rear tires and 4/32 on the fronts..all four tires are wearing evenly all the way across..no cupping and no inner or outer tread wear... seems strange huh? I also had better than 50% of the brake pad surface remaining whgen I replaced the rotors with eradispeeds..

 

Hey Evil, I agree. When you lower you are dropping the body. You are not changing the relationship of the upper and lower arms to the spindle. If this were true then your camber would change under load. I had my car aligned before I lowered and had it rechecked JFTHOI and it was the same. ;)

 

This has been an enlightening topic. I recently lowered my C5 and did not have an alignment done. It is nice to hear that this really was not required.

Lowering will affect how the car rides and a few other things. My experience with the back end was too much lowering and the back end bounced annoyingly. I added some spacer back in and that helped quite a bit. Then I installed the Bilstein Sports on the back (still to do on the front) and the bounce was gone. The ride is very firm.

The very low back really affected my front end steering during autocross. I had a lot of understeer and actually pushed the tires with the wheel turned sharply. This was much harder to do before. With the back raised a little, I am hoping that that aspect is changed. I will add more rear end height if it is not improved enough.

Once I was lowered, I received many comments and compliments. I also scrape an low spots and speed bumps a lot more. As long as I am careful, there is no problem. It is amazing how changed the car looks after lowering.
The nice part of this is that the whole modification is easily reversed, if you decide to go back to the rarified air..... :D :cheers: :cheers:

 

That's an interesting observation from Chuck Broten. I think I'll try to find a deserted parking lot this weekend to see if I can detect any understeer. Don't know if my butt is sensitive enough, but will give it a try. I've often wondered if one of the major physical characterisitcs that make a great racer is a sensitive butt?

 

:confused: Camber DOES change under load, it's measured as "camber gain". You ARE changing the angle of the upper and lower control arms when you lower the car - yes you are dropping the body, but you are also dropping the frame that the control arms are attached to.

FYI, the testing group at GM's proving grounds found that when you lower the C5, the rear end toes out (a poor handling attribute). I know this because I am friends with one of them.

 

Lowering any corvette over 1 inch will increase negative camber front and rear. Most likely the toe will change also.
What I think we are missing here is this:
Some people can lower their car and still be within specs of the factory alignment.
Others are going to lower their car the same amount and find their car to be out of specs and need to be aligned.
Example: if a car is near or at the limit of negative camber before lowering then it will exceed the specs after it is lowered.
If you have access to a camber gauge try this: measure the camber of a rear wheel then put enough weight on the rear to lower it 1 inch. Then check the camber again. I have done this on several cars and I will bet you will change camber by .3 to .5 degrees. Sometimes more.
Hope this helps.
So if you are going to lower your car 1 inch or more, have the alignment checked. It may still be in specs but you will know for sure.


[Modified by corvette dave, 11:09 PM 8/10/2001]