CMS-GT4":16onyie2 said:
Thanks. I checked the rack when I set it up, and it measured centered. I am using a tape measure though, and I would like to look into a more accurate tool for large measurement, preferably in mm. I am just not sure what that tool would be.
You could slide the rack boots down over the tierod and measure the distance from the rack end to the rack casing on each side.
I think that would be the easiest way.
I did take the readings about 4 other times for this side, I just did not record it. I had a lot of recordings of failed measurements as I was figuring out the angle of the frame against the plate. While the numbers were different from the final results, the toe change in and out were consistent at the heights.
I will do the other side once I get the new parts in. My control arm is not right on the other side and has a degree of caster difference, so I will measure that when its replaced.
The height I chose was the ride height I had measured off the car. I made a cap with a slot cut into it to measure off of so my measuring points from the axle would be consistent. Due to alignment at the height the toe change is 0 and is the lowest point but 0 is achieved again at 1.25" of compression. I had looked at some other cars bump steer readings and talked to a couple tuners on the subject, and supposedly its common for a production car to have bump toe changes like that.
I am going to try and measure droop the next time too. The problem I had with that is the shock wheel did not want to drop hardly below the ride height without assistance. I had to put weight on it, and I was afraid I would mess up my reading that way.
Try pushing it all the way to droop (hopefully it'll stay there due to stiff bushes), then use the jack to raise it from droop to full compression.
You need to plot a graph like this, then everything will become clear:
You should get a shape pretty close to that.
In that graph, the 11.5 inch mark is the ideal settled ride height for the minimum amount of bump steer.
So using a graph like that, you would set your ride height to 11.5in, then do a wheel align to set your normal wheel align toe in/out amount (0 for me).
Once you've done that, you'll have the perfect front ride height & wheel alignment to achieve the minimum amount of bumpster.
In other news I tried a camber curve experiment. I have a magnetic digital level used for alignments and I put it on the car and measured and went through the 3" of compression, and 3/4" of droop to see what I get. The gauge is zeroed at ride height. Here is the numbers, and they may also explain why I have more wear on the outside of my tire. I want to do more research on how to test it though. I expected a curve that added negative camber then would go to positive when deeper in compression, but it seems to go straight into positive on compression.
If you corner hard (ie, >1G) a lot, then its a camber/caster issue. If you don't corner hard much, then its a wheel align issue.
Camber change through suspension travel is a macpherson strut weakness. There is nothing you can do about it without completely changing the suspension setup to double A arm.