Again, the issue is not the OD of the tire.

Inflation pressure determines the tire's spring rate.  And that, in combination with the 
load applied to the tire, determines the tire's rolling radius.

The issue is the tire's rolling radius, which ultimately determines the tire's RPM 
(revolutions per mile).

--- On Sun, 27 Apr 1997 11:38:05 -0500  Shawn & Janis Wright <vwnut@smuslabs.smus.bc.ca> 
wrote:

>> From:          Paul Uusitalo <puusital@Adobe.COM>
>> With tire pressures set to VW spec, (take your pick from inside the door
>> jam, I run fronts at 40 and  backs at 48) you must be pretty darn close to
>> the 3mm F to R tire size difference (Tim describes below) that will cause
>> the Syncro's viscous coupling to begin to engage, no?
>> 
>Has anyone tried just measuring the static radius of the tire when 
>inflated this way? It would seem to me that taking an average of 3-4 
>measurements on each tire, from ground to edge of rim, or centre of 
>axle, would indicate how close the front/rear radii are...
>
>Shawn & Janis Wright
>'88 Westy (338k) '85 Jetta TD (375k)
>VWnut@smus.bc.ca  :  swright@smus.bc.ca
>http://www.islandnet.com/~swright/vw.html
>http://www.smus.bc.ca

-----------------End of Original Message-----------------

____________________________________________

  Michael Stocker <mdstockr@neo.lrun.com>   
  North Canton, Ohio, USA
  4/27/97 12:44:33 PM EST
____________________________________________