<VV> Re: VirtualVairs Digest, Vol 25, Issue 36

[Ken Franson]

The 70 and the 80 are percentages of the tire width, the 205, 185, etc. 
are width in millimeters.
A 185-80 would be 80% of 185 mm from the wheel to the outside diameter. 
That's 148 mm,
or 5.83 inches Times 2 for the other side equals 11.65 inches, plus 13 
inches of wheel equals
25.65 inches diameter.
A 205-70-13 would be 11.3 inches plus 13, equals 24.3 inches diameter, 
so it is a smaller
diameter.
You can find a bunch of tire info at 
http://auto.howstuffworks.com/tire2.htm or use the chart
at http://www.musclecarclub.com/library/tech/tires.shtml
-Ken Franson
Arkansas Corvair Club

In regards to tire size... I remember reading somewhere that when you
> go from an 80 size tire to a 70 size, you should increase the other
> number by 20.  Therefore to go from a 185x80R13 to a 70R13 you need
> to get a 205x70R13.  That will keep the height pretty close to the
> same as the 185 tire.  I have not had a chance to compare two tires
> in those sizes side by side, so this info may be a little off.  I
> hope those on the list with more tire knowledge will chime in here
> and give us the straight skinny.  (Letting my age show with that last
> comment).  The tire clown may not have had much tire knowledge.
> Andy Anderson
> --- LonzoVair at aol.com wrote:
>
>   
>> It's got 185-80 13 on it... that's good for the stock size, right?
>> Some clown was trying to talk him into some 185-70 13 tires, but I didn't
>> think those were tall enough... was I right? You can certainly see a difference
>> when driving behind it!
>> Lonzo
>>