Please read through the whole thing if you have the time.
So here is the story. I had a guy who came highly recommended align my CTS-V, but 5k miles later the inside of my rear tires showed a ton of wear from toe. I had the before and after printout. According to his rack, my after rear camber was -1.1 / -1.0 and rear toe on each side was .06 / .06 toe in. All good. I won't bother talking about the front because that is still fine. I checked the car with my own camber gauge and did the 'ol jack stand and string trick to measure toe. What I found was that my front measurements were close to his, as was my rear camber, however my measurements showed rear toe out 3/16" on each wheel. So after going back and forth with this guy and getting the whole "I know what I'm doing....." I go to another shop. Turns out my measurements were right. Now, I know different racks are going to show a little different, as this shop showed camber .1 or .2 degrees different on all sides and .01 different total toe on the front....but, the rear toe was -.62 / -.56 degrees (toe out). Now obviously both toe angles are not going to change that drastically on their own. Both tie rods were tight, no bad bushings, and even if the camber adjustment was not torqued correctly, the rear camber would have gone more negative by the LCA's pushing outwards, which would have actually made the toe go in more, not out.
So..how the hell did this guy screw up? I used to do alignments and even had my SAE certs in alignment and suspension, however it has been over 20 years and I forgot part of it.
So, from what I remember, you get the car on the rack, straighten the steering wheel, tell the machine what vehicle it is, and go through the calibration procedure. At that point you get a baseline reading. So far, so good on my first alignment as the pre readings matched what I was seeing on my old tires. (front toe too far in).
Now for the rear, camber would be first, right? He would have to tell the machine to use a simulated camber measurement and then would jack up the car to get the wheels off the ground and do the adjustment. Now the next part is where I'm foggy. He had to put the car back on the ground and would have to do some calibration to measure the actual camber angle at this point. Now...He reduced rear camber from -1.5 to -1, which would pull the LCA's inward...which would cause the toe to go way outward because the tie rod ends are in front of the control arms. So at this point the toe he showed had to be a simulated measurement and not the actual.
Can anyone explain how this happened? Just so you know, I'm not going after this guy. It was a side job at a dealership, so live and learn on my part. I just want to understand what happened. Thanks!
So here is the story. I had a guy who came highly recommended align my CTS-V, but 5k miles later the inside of my rear tires showed a ton of wear from toe. I had the before and after printout. According to his rack, my after rear camber was -1.1 / -1.0 and rear toe on each side was .06 / .06 toe in. All good. I won't bother talking about the front because that is still fine. I checked the car with my own camber gauge and did the 'ol jack stand and string trick to measure toe. What I found was that my front measurements were close to his, as was my rear camber, however my measurements showed rear toe out 3/16" on each wheel. So after going back and forth with this guy and getting the whole "I know what I'm doing....." I go to another shop. Turns out my measurements were right. Now, I know different racks are going to show a little different, as this shop showed camber .1 or .2 degrees different on all sides and .01 different total toe on the front....but, the rear toe was -.62 / -.56 degrees (toe out). Now obviously both toe angles are not going to change that drastically on their own. Both tie rods were tight, no bad bushings, and even if the camber adjustment was not torqued correctly, the rear camber would have gone more negative by the LCA's pushing outwards, which would have actually made the toe go in more, not out.
So..how the hell did this guy screw up? I used to do alignments and even had my SAE certs in alignment and suspension, however it has been over 20 years and I forgot part of it.
So, from what I remember, you get the car on the rack, straighten the steering wheel, tell the machine what vehicle it is, and go through the calibration procedure. At that point you get a baseline reading. So far, so good on my first alignment as the pre readings matched what I was seeing on my old tires. (front toe too far in).
Now for the rear, camber would be first, right? He would have to tell the machine to use a simulated camber measurement and then would jack up the car to get the wheels off the ground and do the adjustment. Now the next part is where I'm foggy. He had to put the car back on the ground and would have to do some calibration to measure the actual camber angle at this point. Now...He reduced rear camber from -1.5 to -1, which would pull the LCA's inward...which would cause the toe to go way outward because the tie rod ends are in front of the control arms. So at this point the toe he showed had to be a simulated measurement and not the actual.
Can anyone explain how this happened? Just so you know, I'm not going after this guy. It was a side job at a dealership, so live and learn on my part. I just want to understand what happened. Thanks!
