Yup, assuming in your 16x7 example that you're starting with *positive*
offset, and you're wanting to increase your track (you mentioned spacers)
then positive offset will increase (in your example) from 35mm to 42mm, and
your backspace dimension will be reduced from 66mm by the same delta.
But of course, if in your example you *started* with negative offset (which
my car and others have, and plenty of it) but still wanted a wider track,
then the offset number would actually *fall* as you moved in the positive
*direction*. My SVO, which has 16x7 wheels, has 45mm of *negative* offset,
so an increase in track of 1/4" on a side (why bother) would cause my offset
dimension to *fall* to 38mm negative.
That's because *positive* offset is a measure of any amount that the
centerline of the wheel width is on the *outside* of the wheel mounting
surface (more than half the wheel is away from the car), and *negative* is
that amount that the centerline is on the *inside* of the mounting surface
(more than half of the wheel is towards the car).
Confusing, huh? And it's the very abstract nature of offset ("do you *have*
positive offset, and are you changing offset in the positive *direction*?")
that makes *backspacing* an easier measure to use, at least for autox
purposes (darned few wheels available with negative backspacing, though I'm
sure someone will come with some examples). ;)
I hitched my wagon to the SP star, and I run *two to four inches* more track
front and/or rear on my Mustang. Now that's a change worth making (if you
don't mind a little rubbing on the rear wheelwell lip when carrying
passengers, when off the course). :)
Richard Nichols
rnichol1@san.rr.com
86 Mustang SVO TII 1C: ESP/FSP/?
72 Pinto Sedan 2.0 3J - Original Owner, Restored
On display at the San Diego Automotive Museum,
June 99 through January 00
-----Original Message-----
From: Jeffrey Lloyd <jslz3@hotmail.com>
To: autox@autox.team.net <autox@autox.team.net>
Date: Sunday, April 25, 1999 8:20 PM
Subject: wheels which ones?
>I have found A buyer for my current, wheels and tires, I'm ordering a
>new set of hoosiers, so I wan't to find a nice set of superlight
>wheels to go with the light new skins, I also wan't to have the legal
>extra 1/4 inch of offset built into the wheel, so I don't have to
>compromise with a spacer, any suggestions, I need 16x7's I beleive
>the stock is 35mm offset so I guess I want 42mm offset. Right?
>
>thanks
>Jeff Lloyd>
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