I went to a local shop that had fairly new alignment equipment last week and put the car on the rack. Just got a printout and left.
I did this for my own curiosity but thought it would be very useful for forum members.
Last week was spent lowering the car and tweaking each corner because I'm so ****. As soon as I was happy with the height at the corners I took it back to align the car. I was betting it would be out of spec in at least one area.
The alignment was done by the same tech on the same machine. Tire pressures at 31 psi and 7/8 fuel in the tank.
Below are the results, before on the left and after on the right. You can see that after lowering there were 3 areas out of spec.
Here is a picture of the car. The front has been lowered, the rear not yet.


LF
Caster 7.95____________________ Caster 8.26 (out of specs)
Camber -0.12___________________Camber -0.42
Toe 0.14_______________________Toe 0.04
Total toe 0.20___________________Total toe 0.02

RF
Caster 7.47____________________ Caster 7.83
Camber -0.76___________________Camber -0.87
Toe 0.06_______________________Toe -0.02
Total toe 0.20___________________Total toe 0.02

LR
Camber -0.65___________________Camber -0.83
Toe 0.00_______________________Toe 0.14 (out of specs)
Total toe -0.07__________________Total toe 0.04

RR
Camber -0.55___________________Camber -0.74
Toe -0.07______________________Toe -0.11 (out of specs)
Total toe -0.07__________________Total toe 0.04

 

Mine was dead on factory specs after I lowered the car.

 

I just had my car aligned after lowering and I had the EXACT items out-of-spec. Rear toe.

 

The problem you have and a lot of others have had over the years is using the body of the car for your reference. The body isn't mounted on the frame consistently from one car to the next (not a controlled manufacturing point) so all of your reference points are different from car to car. Ride height is adjustable but the measurement is made at the lower control arm and requires a special tool. When you lower the car based on body reference points you can change the corner balance which might affect car handling at the extreme end of the range (on the track or when on the street in an extreme emergency maneuver). Lowering always increases negative camber which then changes the toe settings. You didn't include thrust angle or steering wheel centering which changes with the changes in toe.

I don't know GM's permitted range of settings for the C7 but I can see the initial alignment wasn't well done. There shouldn't have been that much camber difference between the front wheels (-.12 L and -.76 R). The left front wheel was practically standing straight up. It looks like you may have lowered the left front more than the right front so your after camber readings are more closely matched. Reducing the caster on the left front will bring the negative camber closer to the right front which is good from a performance stand point but will increase tire wear. Do you know which way the machine measured toe? Most machines and specification sheets define toe in as positive and toe out as negative but there is no defined standard so sometimes you run into the situations where the signs are reversed. Typically lowering will increase front toe in and increase rear toe out since negative camber increases. The toe results are interesting since you got increased toe in at the left rear and increased toe out at the right rear.

Bill

 

Both the C5 and C6 go toe out in the rear while being lowered and I would have to assume the C7 would be the same. I would recommend that this be corrected before driving and not just because of tire wear but because the handling will be pretty unstable if the total toe is out.

 

Bill,
Nowhere in my post did I say I used the body to make measurements.
I am aware of wedge and rake. I have been explaining this to forum members for years. Most don't seem to care.
Your explanation is well taken.

Here is what I posted in another thread:

The lowering bolts allow the corners to be adjusted about 1/2" to 3/4" up or down. Each car is different from the factory, even a small amount.
If you look at a stock corvette from the factory you will see there are varying amounts of threads remaining on the bolts. As an example, one corner you might be able to turn the bolt 4 turns. Another corner might be 8 turns. The others might be somewhere between those two.
The bolts are not exact to the correct ride height.
Mine were 8, 7, 6, 5.
Lowering the car to the max at all corners does not make the car level.
My advice is to keep the amount of lowering as even as possible side to side front and rear.
Also keep the amount of lowering as even as possible front to rear to keep the factory rake.
You will end up with some bolts at their max and some not.
Mine ended with 2 maxed and 2 not.
Take accurate measurements before turning anything and record them.

 

Dave...how much did you lower f/r?
S.

 

If you lower your car it's a crap shoot on the affects it'll have on your alignment. If your willing to gamble with $1500 worth of tires your a braver man than me.

Tom

 

11/16" rear
3/4" front

 

Not sure what you mean.
I had my car aligned after lowering.
It is aligned better now than it arrived from the factory.

 

I mean many folks don't align their cars and think they are alright. I would never gamble like that.

Tom

 

Actually, it's quite predictable. If it's not, it means you have loose/worn/bent parts.

 

LR
Camber -0.65___________________Camber -0.83
Toe 0.00_______________________Toe 0.14 (out of specs)
Total toe -0.07__________________Total toe 0.04

RR
Camber -0.55___________________Camber -0.74
Toe -0.07______________________Toe -0.11 (out of specs)
Total toe -0.07__________________Total toe 0.04[/QUOTE]

So regarding your REAR TOE specs, where you indicate that the rear changes from negative to positive after lowering, pardon my basic question but does that mean your rear toe went toe in after it was lowered? I thought usually Corvettes go toe out after lowering. Negative toe means toe out and positive means toe in? Thanks.
Dave

 

So regarding your REAR TOE specs, where you indicate that the rear changes from negative to positive after lowering, pardon my basic question but does that mean your rear toe went toe in after it was lowered? I thought usually Corvettes go toe out after lowering. Negative toe means toe out and positive means toe in? Thanks.
Dave[/QUOTE]

Dave,
There is no universal agreement on which sign should be assigned to toe in or toe out. From a GM standpoint Toe In is positive and Toe out is negative. This is something that should be clarified when you are getting an alignment and telling the mechanic what you want. I always show toe in as positive but I also write on the sheet right next to it TOE IN. A case on point are the old Pfadt specs used for the C5 and C6. They had toe in listed as negative and some people were getting toe out instead. Pfadt updated their later sheets with a note that Toe In was negative in their specs. Most people use positive for Toe In but there are just enough that do the opposite that you need to ensure you don't get caught in a failure to communicate situation.

Bill

 

Dave,
There is no universal agreement on which sign should be assigned to toe in or toe out. From a GM standpoint Toe In is positive and Toe out is negative. This is something that should be clarified when you are getting an alignment and telling the mechanic what you want. I always show toe in as positive but I also write on the sheet right next to it TOE IN. A case on point are the old Pfadt specs used for the C5 and C6. They had toe in listed as negative and some people were getting toe out instead. Pfadt updated their later sheets with a note that Toe In was negative in their specs. Most people use positive for Toe In but there are just enough that do the opposite that you need to ensure you don't get caught in a failure to communicate situation.

Bill[/QUOTE]
Awesome info Bill and you confirmed what I was thinking. There needs to be clarification when people use the +/- instead of "in/out" to indicate toe. Thanks for the reply...So that still leaves me with the question then...does he mean the toe went out or in after he lowered his car. lol
-Dave