That’s a good question. I’ve run down that line of thought a few times. Obviously the compound is better. The only real question is the sidewalls. Are they that much softer than a regular tire that it would offset the improvement in compound? I definitely considered it at one point. But then I added 13” brakes, so 15’s aren’t an option anyway.
See, that’s kinda funny. Because the speed rating has nothing to do with handling or traction. It’s literally just whether the tire comes apart or not. It’s tested by pushing the tire against a spinning drum to simulate load and then spinning it up to the rated speed.
