Hi, I've got a 2004 audi a4 cabriolet, and recently one of my wheels has been losing air (at a rate of about 3-4psi per day)

Now, I've got a spare wheel in the trunk, however neither me nor the previous owner knows where it's from. Just from comparing all the visible markings on the side of the wheel and comparing the treads, they seem to be almost the same, with 2 exceptions:

The original wheel had:
"Tread 2 polyester, 2 steel"
"Plies 2 nylon"
"Sidewall 2 polyester"

The new wheel (the one that was in the trunk) has:
"Tread 1 rayon, 2 steel"
"Plies 2 nylon"
"Sidewall 1 rayon"

Also, the new wheel seemed to be a little bigger than the old one - when I stood them together side by side without any weight on them, the new one stood almost a centimeter higher.


My questions -
1. Could the height difference be due to the new one having less wear?
2. Will the height/wear difference be a problem?
3. Can I continue using this new wheel in the long term without damaging the car?
4. General advice?

thanks

- will

 

1. It's certainly possible but it's more like that it's just due to it being a different type of tire altogether. It's also possible that you need an alignment.
2. Yes, if you have the Quattro and the tire you're putting on is more than 4/32'' of an inch taller than the other tires on the car. The all wheel drive system requires that the tires be close in the overall diameter/revolutions per mile otherwise it creates tension on the drivetrain that can be damaging.
3. See above.
4. The info you listed is just tire construction differences which doesn't have much if any bearing on the issue. I would definitely recommend using the same tire on all four corners of the car so if you can match to what you already have that would be ideal. You can even have a tire shaved to match your current tires tread height to prevent those revs per mile differences.

 

I should have specified that my audi is *not* a quattro, and the new wheel replaced one of the rear wheels.

Also, all 4 wheels say "Pirelli P235/45 R17 P6 Four Seasons". What do these numbers mean?

 

To put it simply, the first numbers "235" are the width in millimeters while the second set "45" are the percentage that determines the height. What is literally means is 45% of 235 is the height of the sidewall. "16" is the wheel size and P6 Four Seasons is just the name of the tire.

Here's a great resource for a lot more detail:
Tire Size Guide