Originally Posted by SMSgt B
and I always thought it had something to do with the speed rating of the tires.
Nope, that's a different story. In Switzerland (and probably also in other countries) you have to use tires that are certified for the maximum speed of your car. (kind of stupid that I have to buy tires certified for 250km/h, even though the national speed limit is 120km/h, but that's the law)