Back from alignment and a question

[Theshandman]

Kevin at Roland Tire in Jasper (GA) did a fantastic job aligning the front end. I go-carted the Roadster a few miles to a place where we could get the car on a U-Haul auto trailer for the trip into town and back. After alignment and back in the neighborhood, off the trailer and home: what a difference! Our build initial alignment was close and the car drove reasonably well. But after the align job, wow. Huge diff. But- Kevin pointed out a -0.38 degree thrust angle at the rear (live) axel. The lower control arms are not adjustable so no correction can be made with the hardware as is.

So- does -0.38 thrust angle sound problematic to anyone? It seems hardly significant but I have no idea what's acceptable. I did not notice any "dog walking" to any degree as I drove back to the house. Length adjustable LCAs would solve the prob but really?
Art

[CraigS]

To me that # seems well within acceptable norms. You already know what would be needed to fix it. One somewhat less expensive option would be to slot one of the rear LCA frame mount holes. Then get a longer bolt and a pair of hardened washers, set it where it needs to go and weld the washers in position. But this is one of those cases where I would wait til you get it on the road, get several hundred miles on it, and see if you notice any drifting one way or the other.

[Jeff Kleiner]

The only thing a small amount of thrust does (and .38 degree is a small amount) is affect dynamic vs stationary steering wheel centering.

Jeff

[FLPBFoot]

0.38 degrees is very small. Mine was close to 0.5 inches! I went with the Breeze adjustable lower control arms to dial it out. Added benefit is they have Heim joints on both ends so they move very smoothly and to me seem to help with the ride.

[J R Jones]

Kevin at Roland Tire in Jasper (GA) did a fantastic job aligning the front end. I go-carted the Roadster a few miles to a place where we could get the car on a U-Haul auto trailer for the trip into town and back. After alignment and back in the neighborhood, off the trailer and home: what a difference! Our build initial alignment was close and the car drove reasonably well. But after the align job, wow. Huge diff. But- Kevin pointed out a -0.38 degree thrust angle at the rear (live) axel. The lower control arms are not adjustable so no correction can be made with the hardware as is.

So- does -0.38 thrust angle sound problematic to anyone? It seems hardly significant but I have no idea what's acceptable. I did not notice any "dog walking" to any degree as I drove back to the house. Length adjustable LCAs would solve the prob but really?
Art

Given the magnitude of error it could be hard to evaluate from the driver's seat. I have found dog tracking is more easily identified by following your vehicle. By aligning your line of sight with the left and right sides, you can see how the rear tires follow the front. Staggered tire sizes make it difficult but side to side comparison can be effective.
GM X series cars were prone to rear sub frame failure at the spring mounts that caused dog tracking, but some drivers seemed to be oblivious.
jim