Miata Mailing List: May 1994, Message #108
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   From: strick@merle.acns.nwu.edu
Subject: offset/backspace
   Date: Thu, 5 May 1994 21:07:31 -0400

My question today has to do with the relationship between wheel offset and
"backspace."  As everyone knows, the beatiful new wheels on the '94 Miata are
14x6" with a 45mm (1.77") offset.  With this information in hand, I called a
company called FastWheels in Tulsa, OK, hoping to order some wheels for my new
Yokohama autocross tires.  They told me they didn't work with offset figures
and asked me what the "backspace" was.  I said I didn't know, but would
measure it for them if they would tell me how.  I thought I understood their
instructions, but every time I called back, they were unhappy with the numbers
I gave them.  (These were mostly in the range of 5-5.5").  Then I called Tire
Rack (who have always been very helpful) and was told that the "backspace"
could be derived by adding the offset (1.77") to half the wheel width (3"). 
We get 4.77".  Let's say 4 3/4".

My question is:  Is this right?  If I order wheels with a 4 3/4" "backspace"
are they going to fit properly?  Why isn't there one standard measure of wheel
dimensions?

Stuart Strickland
strick@merle.acns.nwu.edu

p.s.:  I asked the local dealer about this.  He was dumbfounded, as always.