The tire sidewall can be calculated by multiplying the width (225) by the
aspect ratio (.55 or .60).

The difference is about 13 mm, or 1/2 inch in the sidewall, or about 1 inch
across the diameter. This is significant. The door post should have a
sticker that tells you what the tire options were. My car (a '94 3 Series)
came with the sports package that included 225/55x15. It turns out that this
tire size is now very rare, and replacements come at a price premium. I went
on eBay and found a set of 17" rims from a '95 M3, and the tires are now
225/45x17. The overall tire diameter is within one-quarter inch of the stock
size, so I am in good shape.

I think that your choices as factory fitment are going to be the 225/55 or
205/60, but not 225/60. The difference in the 225/55 and the 205/60 is less
than 1.5 mm on the diameter. 225 x .55 = 123.75 mm, 205 x .60 = 123 mm. 0.75
mm on the radius (or sidewall) is 1.5mm on the overall diameter. If you went
to a 17" rim and kept the 225 tire width, then you would want to buy a
225/50x17 to have essentially the same size tire overall.

A 225/55x16 is an overall diameter of 26 inches.
225 * .55 = 123.75, or 5 inches. This is one sidewall. The rim is 16, so the
rim plus the sidewall on each side will give you the overall diameter of 26
inches.

Using the same formula for a 225/50x17 gives us a sidewall of 112.5 mm, or
4.5 inches. 17 + 9 = 26, so the overall diameter of a 225/55x16 is
equivelent to a 225/50x17. If there was a significant difference in the
price of the tires, the cost of the new rims could easily be recovered by
the time you purchase the second set of new tires. You can see the wheel
options here, http://www.wattora.com/Mods/OBDII/, and you can find rims on
eBay if you search for BMW OEM 17" WHEELS, you might have better luck if you
include your model, E39 or whatever your car is. My car is an E36, so I
searched for BMW OEM E36 17" WHEELS. This search excluded aftermarket rims
and rims for the 5 and 7 Series.

You could also consider a 235/50x17, or a 235/45x17. The /50 would give you
a half inch taller tire and the /45 would give you a half inch shorter tire.
The difference in diameter calculates into the circumference, and by
extension into the final drive ratio. I would go with the slightly smaller
diameter if I was faced with the choice, but a half inch in diameter is
nothing in the grand scheme of things.

You could also work the calculations for 18" wheel options.





"Stan Dowiat" > wrote in message
...
> My 97 528 in riding on tires sized 225/55/R16 tires. The inside of my
> wheels are stamped 7Kx16. The manual states that the tire specification
for
> this is exactly what is on the wheels; 225/55/R16.
>
> When I research tires I find that there seem to many more 225/60/16 tires
> available than 225/55/16. A local BMW mechanic is adamant that 225/60/16
> are what is supposed to be on this car.
>
> I suppose the wheels could have been swapped, however they are BMW wheels
> and seem to be about the correct age ( base on what I think the wear
should
> be ). This wheel is aluminum and has 20 ribs in it.
>
> What do you think? Was this wheel common on a 97 528? Could my car
> originally have come with tires sized 225/60?
>
>