[MetroMPG]

Just did a quick calc to determine how accurate the measuring-tape-across-the-treads method of checking alignment specs for my car would be:

With my 155/80 r13 tires, the outer diameter is 22.76 inches / 578.2 mm, and a 1 degree toe angle equates to a 5 mm or 0.2 inch difference at the tread. That's coarser than I would have guessed, so probably worth a check.

The larger your tires' outer diameter, the more potential accuracy in the measuring tape quick check.