As others have said, rapid rear tire wear is a fact of life with rear-drive mid-engined and rear-engined sports cars. That said, there are things you can do to minimize tire wear. First thing I do before swapping in new rear tires is to get an alignment check. Too much rear camber will increase wear. Tire pressure is also important, you need to monitor it every week or two and keep it correct. Over or under inflation will cause uneven wear and premature replacement. Driving style is obviously a factor, but IMO, Porsches are meant to be driven hard and if you're going to tiptoe around to avoid tire wear, you'd be better off in a Toyota
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Tire selection is a major factor. Kuhmo's are cheap, but from my experience, they require frequent balancing. I suggest doing a road-force balance to start with to minimize re-balancing issues through the life of the tire. Pilot stick great but wear like erasers. I've had extremely good luck with Goodyear Eagle F1 GS-D3 tires. They wear well, stick great in dry or wet conditions, stay in balance, are reasonably quiet, and are cheaper than Pilots. This tire may be or is already phased out by Goodyear, hopefully, they're offering an improved replacement.