Originally Posted by babydriver
So to kind of clarify, I am not saying no tires are ever better than the primacy HP, but that primacy HP are decent tires, comparable to the UHP class. Whenever people talk about track times, and look up the real data, and see that the fr-s times are kind of meh, everyone always says, "it's on prius tires, put it on better tires and it'll beat <insert car here>". And I'm saying that's not quite true. The primacy HP gets very reasonable OEM tire times. While you can improve on it, it's not like swap to a reasonable streetable summer tire and all of a sudden it jumps to the M4/mustang gt whatever class.
So to clarify further, tires are generally grouped in vague classes. Yes the best tire in one class may be faster than the worst tire in the class above, but the classes work decently well. They go (roughly)
Racing Slicks
DOT legal racing slicks
DOT legal track tires
Extreme Performance tires
Maximum Performance tires
Ultra High Performance Tires
High Performance Tires
All the other Summer tires
Everything else
So the Primacy HP, even though they are classified as GT touring summer tires, they actually get decent lap times, in the UHP range. The Dunlop direzza star spec are in the Extreme Performance category, 2 steps ups. They weren't great EP tires, and why they killed it quickly and developed the star spec II, but they weren't bad. Very few cars come out of the factory with OEM EP tires for a lot of reasons. But when you start saying a car on XXX tires is faster than YYY car, then it's not quite a same comparison because both cars are now running different tires. getting 2 seconds from a tire to a EP tire is actually not that impressive. It's pretty standard, and some cars can see a lot more benefit.
PS. a lot of people, especially older people, use UTQG as a vague marker of grip. It is no longer really valid. It used to be roughly okay, but tire tech has tremendously improved in the last couple of decades. The modern push, especially in the performance driven tires, is fueled by autocross and club racing, which usually has tire classes based on UTQG. So that's why there are certain UTQG's that tires come out in. But a modern tire with high UTQG may outperform an older tire with worse UTQG. For example, the Nitto NT05 has a UTQG of 200, but it's currently one of the best EP tires, and faster than tons of tires with UTQG's in the 100's, and faster than older tires with UTQG's under 100. It was specifically designed to hit that 200 goal so that it can run in certain "street tire" car classes. This is also party of the reason that when looking at fastestlap times, it's important to look at cars produced in similar years. Tires keep getting better so lap times keep dropping, and they don't go back and retest old cars on new tires.
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