255/40/17's - S-03 v. S-02 - Tread width difference is HUGE! Why?

[Chiung]

I am in the market for a rear set to replace the S-03's I currently run, and was doing some research on the S-02's. In this size, the S-03 has a tread width of 9.4", while the S-02 (Porsche spec) has a tread width of 8.0". This is a huge difference, especially for a tire of the same "size".

Just for reference, I looked at the Goodyear F1 in this size, and it has a tread width of 8.2".

Are the S-03's that much wider for real or is this a typo (straight from Bridgestone's web site)?

Anyone run the S-02's in this size?

Thanks

[Grant@tirerack]

There are a number of reasons for the tread widths listed. On Porsche spec tires they are made for Porsche and can vary quite a bit in actual dimensions from normal tires in those sizes. Another tire like this is the stock SO-2 on the Honda S2000. The rear tire on that car is almost 3/4" wider than any other tire in that 'size'. When looking at the metric sizes it is important to keep in mind that this is only a range. It is not always the specific dimension. That's why they can be all over the board withing the same size. Each manufactuer uses a different way to measure the tread width as well. Some go from the outer shoulder if the tread blocks extend past the edge and others use only the flat surface of the tread.