Research And Comparison

[Autoxdriver]

width of body / width of front tire

Your only known is width of front tire. It's on a post somewhere.
Take a look at a head on picture, scale it any way you wish.
Give the number one to the width to the front tire and divide it into the width of the front end and multiply that by the real width of the tire.

But this may only work late on a Saturday night just before leaving the bar.

Yep I already planned on doing that if it wasn't known. The front wheel track is 66.8".

 

[Craig]

Yep I already planned on doing that if it wasn't known. The front wheel track is 66.8".

That'l work to. Find a head on picture, mark on a piece of paper the track, divide it into 66.8 segments and use that for your ruler.