I am learning how to perform an alignment on my C7 at home for upcoming track days. I think I have decent understanding of the process, but we'll see how it goes in practice. Using the string method looks pretty straigtforward to ensure the thrust angle measures at 0 degrees. Are there any other methods to setting the thrust angle without strings? All the toe plate kits don't seem to account for thrust angle. If the string method is best for thrust angle, then it does not make sense to purchase a set of toe plates, I should just use the strings and buy a good camber tool. I apprecieate hearing all your thoughts.

 

You can measure thrust angle without strings if you have a two foot long digital laser level and a pointer/tape measure. With two people one person places the laser level across the rear wheel pointing toward the front of the car. The other person places the pointer or tape measure in the center of the front hub and holds it horizontally. The person holding the laser moves it until the laser dot hits the pointer/tape measure. At that time the person holding the tape measure memorizes the measurement and both of them move to the other side of the car where they repeat the same process. When the measurements are within one-eighth inch of each other you have close to zero thrust angle. Incrementally change toe while monitoring thrust until you get the toe setting you want along with the front measurements being within one eighth of an inch of each other.

To do this yourself you need to use toe plates across the rear wheels and place the laser level on top of the toe plates with one side against the tire/wheel. Then use something like a jack stand to hold the pointer or the tape measure. I use a small combination wrench (13 mm) that I use under the level to provide a vertical angle so the laser hits the tape measure. My laser level has magnets on the bottom so the wrench sticks to it and the ledge at the top of the toe plate is wide enough to let the wrench/level combination balance there.

The advantage of using the digital laser level is it can also be used to set camber by placing it vertically on the tire. When you are at the track all you need to do an alignment is the laser level, toe plates, 3 tape measures, and a jack stand. Once you have a level spot to work in with the car being level from side to side you are capable of doing a quick alignment change.

Bill

 

Thanks Bill. I'll have to try out this method as well. It's going to take some practice.

 

This is how I started doing it on a previous car. See the laser dot on the white board near the front wheel.
by https://www.flickr.com/photos/152454123@N04/, on Flickr
by https://www.flickr.com/photos/152454123@N04/, on Flickr
I have upgraded a little in the last 2 years to this setup. And have 2 of the white boards. The end of the pvc pipe is sized so it fits over the bolt head that attaches those 1/4" x 1.5" aluminum reinforcer pieces near the rocker panel area.
I have made up two of these to go with the pair of white boards.
by https://www.flickr.com/photos/152454123@N04/, on Flickr
I once had a chance to work w/ a couple of guys using the string method. As far as I am concerned it sucks. You do too many eyeball comparisons of a string to something just setting up the strings and more eyeball work measuring to your wheels. And usually, to make any changes, you have to move the strings out of the way to jack up the car and make your adjustments. My camber/caster is from Longacre
Longacre Caster Camber Gauges (longacreracing.com)
The laser is Klein from Lowes or HD.

 

I use a really long 1x4. The relative angle over 105" is very easy to measure. If you get within 1/8" (side to side) you are fine. I used to use lasers, but the 1x4 if faster and just as accurate

Once you get symmetry, just make your toe adjustments symmetric. You can zero the steering wheel and measure the backward "thrust angle" as well.



Keep it simple

 

David I used to use long pieces of wood trim also. I agree it works fine. For me the advantage of the laser is that I can see it move while I twist the aftermarket toe link. I am lying on the floor w/ the car on 2x10s and at 73, any time I can cut out a 'get up off the floor' procedure I do.

 

I have been doing 4 wheel alignments for over 30 years with a Hunter aligner. And i can not see how you can do a 4 wheel alignment on the floor with string and wood to specification. How do you adjust rear camber?

 

That just takes a lot of work. Measure, raise the car, adjust lower control arm cams (hopefully, just enough adjustment), lower car, take it for a drive around the block to settle the suspension, and then remeasure camber and repeat until you get it correct. Camber and caster make it more interesting.

One of the things I have done is leave my camber gauge connected to the wheel and I see how much it changes as I lift the car. Then I make my adjustments relative to the number I see once the car is lifted. So if I wanted to change the camber from -0.9 degrees to -1.4 degrees when the car is on the ground I would then move it -0.5 degrees from the reading I see with it off the ground. It can take a long time to do the job with the car on the ground and it is a real PIA crawling under a C7 to measure rear caster when you are 80 years old, the floor is cold and hard and there isn't enough room to get your shoulders under the car or to reach up to the knuckle and insert the rear caster gauge adapter.

Bill

 

Bill you are 100% correct. It's not much more fun at 73. I like to run autocrosses and I like a lot of negative camber for them. But that wears the inside of the street tires the other 4-5 months of the year. My recent project was to get the car set at the autocross camber w/ 0 or 1 washer behind the UCA mounts. I then made up extra thick washers to get the camber to 1 deg or a little less for the winter. So now I can pop washers in and out and just need to reset toe. SO much nicer than using the dang eccentrics on the LCAs.