They're just really, really good.
I remember thinking one day about how the important parts for the Escudo (engine, drivetrain) were generally top notch, and wondered if the less important parts were just as good. The regular upgrades aren't noticeably better than any others, but the super soft tires have incredible grip compared to that of the kind of cars I tended to hybrid most (low and mid range cars, mostly).
Sometimes the hybrided car had so much grip it couldn't accelerate properly (like what happened when you set the car's grip too high via code) and sometimes they ended up with WAY too much oversteer, but mostly it worked great. The whole range of Escudo racing tires were really good, if I remember right. Seems like the GT-One tires were pretty good too.