Frank,
Well yes, you are right - sort of. Puhn's "How To Make Your Car Handle",
which I bought in 1978. Page 126, Figure 34, has a nice drawing and a
detailed caption showing negative is in and positive is out. The adjacent
text also says "Wheels built so the center of the rim is inboard of the
wheel-mounting surface, called 'negative offset', makes the track narrower."
Puhn was consistent, but backwards from the 1968 SAE spec. And Puhn is
where I first learned about offsets, and it stuck. And this was reinforced
by my wheel purchases from American Racing, CenterLine, and Saber Wheel, who
all referred to offsets in the same way Puhn did.
Somewhere along the way the wheel industry has changed to the SAE
terminology, but I hadn't noticed. As you go back in time, more and more
books use the opposite convention to SAE. For example, Tim Remus' "Boyd
Coddington's How To Build Hot Rod Chassis" from 1992 says, "OFFSET: This is
where it gets confusing... Whether offset to the outside of the car should
be referred to as positive or negative depends on whom you talk to." Or
apparently when I might add. Sometime between 1993 and the present common
usage seems to have swung to SAE's convention.
Thanks for pointing this out. I guess I'll try to re-educate myself. But
just one more reason to use backspacing instead of offset.
Bob
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