more ?s about tires

[Robert Myers]

At 08:04 AM 10/11/00, you wrote:

>Hi gang,
>
>Just wondering if someone could clarify something for me.  The Tire
>Rack person I spoke to suggested a set of 15 inch snows despite the
>fact that my summer wheels are 16 inch.  Specifically, they suggested
>195/65QR15 Blizzak WS-50 tires mounted on steel wheels.  My '01 A4
>sport package came with 205/55ZR16 Dunlop SP8000E tires.
>
>Is the outside diameter of these two tire/wheel combos the same?  The
>Tire Rack guy said no problem.. but I want to double check before I
>mount these.  Can anyone point me to a good URL which explains what
>all these numbers actually mean?

Outside diameter is diameter of the wheel plus twice the "thickness" of the 
tire.  The units need to be the same in all comparisons.  The numbers 
195/65 say that the "thickness" of this tire is 65% of 195 mm (or 126.75 
mm).  The diameter of the wheel is 15 inches (or 381 mm).  The OD will be 
381 + 2*126.75 = 634.5 mm or 63.45 cm or 24.98 inches.

The same calculations for the 205/55R16 give 406.4 + 2*(.55*205) = 631.9 mm 
or 63.19 cm or 24.88 inches.  Approximately 0.1 inch difference is 
essentially insignificant.  The tire salesman is correct.


>A Quattro with serious snow/ice/mud tires should be just about
>unstoppable, I would think.. although the old joke may apply: with 4
>wheel drive you can get stuck so badly that nothing short of an Army
>helicopter can get you out.  ;-)
>
>Thanks,
>Bob
>
>
>
>
>---
>Incoming mail is certified Virus Free.
>Checked by AVG anti-virus system (http://www.grisoft.com).
>Version: 6.0.198 / Virus Database: 95 - Release Date: 10/4/00

Bob
*****
  Robert L. Myers  rmyers at oak.total-web.net     Home 304-574-2372
  Rt. 4, Box 57,  Fayetteville, WV 25840 USA   WV tag Q SHIP
  '95 urS6  Cashmere Grey - der Wunderwagen    ICQ 22170244
  http://www.cob-net.org/church/pvcob.htm  MediaRing Talk 304-574-1166
*****