[Vwdiesel] Tire size conversion

[Roger Brown]

LBaird119 at aol.com wrote:
> 
>   Sounds good but isn't the /xx number the aspect ratio of the width/diameter
> 
> rather than the width dimension itself?
>   Sort of diameter/(width divided by diameter) R wheel diameter.   (where the
> 
> slash mark is not a division symbol.  Rather than diameter divided by
> width R wheel diameter.

Its the aspect ratio of the tire, or ratio of the section height to the
section width:
	http://www.4crawler.com/Diesel/Tires.shtml#SIDEWALL

For the given tire, 27x8.5R14, the overall tire is 27" tall, 14 of the
inches is the wheel, leaving 13" of actual tire height, split with half
on top and half on the bottom of the wheel, so the tire section height
is 13/2 or 6.5".  Aspect ratio is then the ratio of the section height
to the section width or 6.5"/8.5"=0.76 or 76%.

The "metric" tire designation has to be one of my "favorite"
must-have-been-designed-by-a-committee specifications, you have a metric
section width (in millimeters), a dimensionless aspect ratio followed by
an imperial wheel diameter (in inches).  Makes everyone feel good but
tells you very little about the actual size of the tire.

-- 
   Roger