I replaced my Goodyear Eagle F1s, which I'd had on since the car was new, with the Firestone Firehawk SZ90u to try and save a few quid. But as soon as I drove away from the garage I could tell the difference. The car seemed more bouncier as I steered (not in a good way) and felt unstable. It felt like the car was swaying. I beared with it to see if it was just psychological but when I took some corners at what I deemed to be my usual way, the traction control would come on and the car didn't handle anything like it did with the Goodyears. I had never really noticed much difference in handling over the years when I've changed my tires but maybe as I'm driving a faster, sportier car that I enjoy driving well maybe this is the difference. I was that concerned I took my car back to the garage to ask them if they could check that nothing had been disturbed or fiddled with when changing the tires! A technician came out with me and drove the car but he couldn't notice anything wrong with the way it handled. I can only put it down to the difference in tires and when they showed me the difference in the side wall firmness between the Goodyear and the Firestone, the Goodyear are reinforced and solid, preventing rolling and improving stability. The Firestones have now worn on the outside circumference (fronts only) after approx. 13,000 miles, requiring replacement. The rest of the tire and the rears have plenty of tread left on them but I am putting Goodyear Eagle F1s back on the fronts for now and the rears when they're also worn. Hopefully I will get the trusty road holding and handling I was accustomed to again..