Current Recommendations On Home Wheel Alignment Equipment?

MDchanic said
Okay. That makes sense. I never tried to work any of this out on paper (if I could even remember how to - Geometry was a LOOOOOOONG time ago), so that's helpful.

Probably needed if you want to check for runout, though. I don't remember whether that was part of the process, but I do remember adjusting a thumbwheel that moved one level tube, then rotating the wheel and doing that again. I think. It's been like 30 years...

- Eric

Runout has to be checked for the toe, if you’re using the wheel attachments/adapters for an optical gauge or similar. It also confirms that the wheel attachments are in fact parallel to the wheel face. But for camber and caster you should be able to see if the wheel adapters aren’t flush.

92b said
Also just thinking outloud. I don't think it would matter on caster swings where the gauge is vertically as long as it is still centered with the hub. I'm not sure if that would hold true horizontally or front to back for caster swings. In my head I'm picturing an extreme for effect. If the gauge could be slid back from centered all the way to near the bead of the tire. I'm not sure it would read the same. I know this is not a realistic example, just an extreme for the thought experiment.

So the SPC fastrax gauge that I use basically reads off the bottom attachment at the lip of the rim, not at the center.

Because of the way it attaches it should still pass through center, but the gauge doesn’t even have a level going the other direction to confirm it’s parallel to the ground.

By zeroing the camber reading with the wheels turned, and then reading it turned the same amount in the opposite direction you cancel out pretty much all the geometry except for the angle of inclination which is your caster angle.

It’s been a long time for geometry proofs for me, but because you’re taking the difference between those measurements it cancels out a ton of variables.