Re: A question of lineage...

[zm@mhcnet.att.com (Zafer Mehmood [209])]

Hopefully I can clear some of the mystery surrounding the various tire sizes.

The history so far...

GCIRILLO@aol.com said that his 91 Audi 90 20V came with 50 series
tires (actual size not mentioned) which he replaced with 215/60/15
tires. The problem was that the wheels look stuffed in the wheel wells.

Eliot Lim replied:
> the correct size (according to my brochure) is 205/50 VR15.. 215/60 is much
> much taller.. i suggest you get rid of these tires because they are more
> than a little oversized.. 215/60 is what they put on the V8!  (and the S4/S6
> if you specify "all-season" tires)

Andrew L. Duane wrote:

> Well, we just got a 1990 20V 90Q, and it had the Pearl White
> BBS alloys, in 6x14, with 195/60/14 (185?).
> What gives?

If 205/50 VR15 is the specified size for the '91 90/20V (check the manual
or sticker on car - on my car, the sticker is on the inside of the gas
filler flap), 195/60/14 that Andrew got on his car is a suitable replacement
for all-weather use because the outside diameter of these two wheel sizes
is virtually the same. The 215/60/15 that GCIRILLO put on his car are
clearly too big (over 2" too big in diameter). No wonder they look stuffed.
The speedo reading will also be erroneous. As Eliot mentioned, they should
be replaced. May be you can get the Goodyear guys to swap them for the right
size since they should have advised you appropriately.

Here are the sizes of three tire specs in question:

Specification  Sidewall  Radius  Diameter  Circumference  Revs/Mile  Difference
205/50-15         4.0in  11.5in    23.1in         72.5in        874        0.0%
195/60-14         4.6in  11.6in    23.2in         72.9in        869        0.6%
215/60-15         5.1in  12.6in    25.2in         79.0in        802        9.0%

BTW, here's what the spec 205/50-15 means:
 205 is the tire width in mm
 50 is the aspect ratio or "profile", i.e., sidewall height is 50% of tire width
 15 is wheel rim size in inches

-----------------------------------------------------------------
Zafer Mehmood				   AT&T Bell Laboratories
zm@mhcnet.att.com			   Murray Hill, NJ