Trips......sorry to disagree with you on this one.....but Sorex (and other brands of rubber tires) do NOT slow down on carpet or asphalt after the first 3-4 runs.
My year old 20/24/28 sorex tires are as fast as any other tire out there...bar none.....and not because they are mine either.
.....and this is not the "defend the Sorex tire" club either.
We run in hot weather on the asphalt as well.......the Sorex does NOT slow down like other name brands.