200 wheel fitment

George Selby gselby4x4 at earthlink.net
Thu Oct 13 11:57:42 EDT 2005

At 10:19 AM 10/13/2005, you wrote:

>I may be wrong, but backspacing is measured from back of rim (hub mounting
>surface to) to "back" of rim. Meaning, there should only be a 3mm difference
>between the 45 and 48 ET. (Rim width is irrelevant!)
>I'd be more concerned with fender to wheel and tie rod/strut steering

Ah, there are two ways to describe where the wheel mounting surface is on a 
wheel in relation to the center.  The two common methods are backspacing 
and offset.  Backspacing is the "old" way of measuring this spec, and it is 
measured from the back of the wheel (thus the name backspacing.)  This is 
typically how they describe 4x4 truck wheels, and it is usually expressed 
in inches.

The other method is offset, and is used by most everyone now.  It measures 
the offset from the center of the wheel, typically in mm.  A positive 
number means the mounting surface is more towards the outside of the wheel, 
and negative towards the inside.  So a larger ET (offset) number means the 
wheel surface is more to the outside of the wheel which moves the rest of 
the wheel in towards to car.

Further proof I'm right:  If ET45 meant a 45 mm backspacing, this is less 
than 2 inches.  Is the wheel mounting surface less than 2 inches from the 
back of the wheel?  No, it is more toward the outside.  So I'm pretty sure 
my math was correct.

I also wasn't to worried about fender clearance, as I already have a set of 
tires that are taller than stock on my car.  Even with 17" wheels, my 
desired combination of 225/45R17's and 17" wheels would be smaller in 
diameter than what I've got on there now.

I eventually came to the conclusion that even though the wheel itself would 
fit, the tire would either hit or be extremely close to the tie rod 
end.  Further proof of this was evidenced by investigation www.tirerack.com 
and www.discountiredirect.com.  Tire rack didn't even have a 17" wheel for 
a 1990 200, and Discount TD showed that largest size fitting as being a 
17x7.5, with a ET35, which I feel indicates a 17x8 ET 48 would have 
clearance problems in the inside (probably with the tire.)

The point is moot now, though, as the wheels are gone.

George Selby 

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