tire sizing help

[Tessie McMillan]

Ben, I can give the "Dummies" version of tire sizing! &:-)

I would start by checking to see what the OEM wheel/tire size was for 
your car. I think you can find this information on the Audifans Web site; 
you just need to ferret around for your model number and year. The OEM 
wheel size and tire profile will determine ... guys correct me if this is 
the wrong term... rolling radius for your wheel. You want to come up with 
an aftermarket wheel plus tire profile that matches the OEM. This way you 
can still trust your odometer/speedometer. I would expect for your car it's 
something like a 50 profile on a 15" wheel or 55 profile on a 14" wheel.

To read the "somethings" is like this: 205/50 x 15 refers to the width of 
the tire (205), the profile (50), and the diameter of the wheel it fits 
(15). Profile refers to the sidewall height of a tire. I think a larger 
profile can produce a more compliant tire, and a shorter profile a less 
compliant tire. 55 is a larger profile than 50. If you go to a larger 
aftermarket wheel, you might need to go to a lower profile tire in order 
to keep the rolling radius the same. I just did a search on google and 
came up with the following calculator; this one looks kind of 
promising:  http://www.csgnetwork.com/tireinfo4calc.html. There  might be 
better ones out there.

If you can find any mfg info on your current wheels, that might lead you 
to discern how wide they are. 215 is a little wide in my opinion (I have 
225s for my 911, but not on my Audi!). The width of the wheel will tell 
you the width of tire you need to purchase. For a SNOW tire, I would expect 
that you'd want the narrowest possible tire (maybe 195?), NOT the widest. 
I don't drive much in the snow but I seem to recall that all the 
variables are different in the snow -- and the less of a footprint you 
present in the snow, the better for your traction. I had thought that 
snow tires for rally cars were always the skinny ones... &:-)

A good source of info on tires (for example, what do all the other letters 
on the tires mean?) is the Tirerack.com Web site. 

Hope this info helps!

Tess
in Bellevue, WA USA.