more ?s about tires

[Andrew Duane USG]

Hairy green toads from Mars made Bob Trevithick say:

> 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?

Tire Rack explains them all pretty well on their web page.
Here are the actual sizes:

# tire_size 205/55ZR16 195/65QR15
Specification  Sidewall  Radius  Diameter  Circumference  Revs/Mile  Difference
205/55-16         4.4in  12.4in    24.9in         78.2in        811        0.0%
195/65-15         5.0in  12.5in    25.0in         78.5in        807        0.4%

So they are almost exactly the same size. 0.4% is insignificant.

-- 

Andrew L. Duane (JOT-7)			duane at zk3.dec.com
Compaq Computer Corporation		(603)-884-1294
110 Spit Brook Road
M/S ZKO3-3/U14
Nashua, NH    03062-2698

Only my cat shares my opinions, and she's too psychotic to express it