Heyer on Tires

Most modern-era Porsches left the factory on high-performance Pirelli or Michelin tires. This rubber tended to be remarkably effective, but it was never cheap - and aggressively driven cars use up tires a lot more quickly than the average econobox.
  Rear-engined Porsches usually wear out their rear tires more rapidly than their fronts. Over the years Heyer Performance has noticed that a lot of owners replace the two tires at the worn end with stock OEM (Original Equipment Manufacturer) units: That is a fine strategy, but OE-type tires are usually marked up. Since your Porsche was designed to really use its rubber, think about replacing all four tires

with comparable non-OE performance rubber for about the same cost. (Don't hesitate to consult Heyer Performance for tire advice: Tony recommends both Yokohamas and Bridgestones for regular and fast road use.) This option won't cause the sticker shock of replacing four stock tires, and you'll have fresh rubber at both ends.
  Looking to really enjoy your summer driving? Tony is especially enthusiastic about the current range of 40treadwear racetrack/DOT Toyos, a relatively inexpensive tire that offers exceptional grip. Of course, fun has its price. These Toyos wear faster than anything you might normally run on the street and kick up more gravel.

Tony on Tire Pressure

Ah, the sands of time: Time affects your tire pressures as the rubber stretches and contracts with heating and cooling. As a result, tires usually lose about one psi per month. Over the course of six months that seemingly small amount adds up to a significant loss in pressure.

Underinflation puts a strain on the sidewalls due to additional flex. It also generates uneven tread wear and may reduce overall tread life by as much as 25%. Underinflation even causes a notable rise in internal heat and an increase in rolling resistance. The result is reduced fuel efficiency and tire life for your Porsche.

Temperature can also affect tire pressure. That's less ofa concern here in the Bay Area with our mild climate, but in regions with harsher weather it's worth keeping an eye on. Just so you know, every 10 degrees Fahrenheit equals one pound of tire inflation: If you set your tires in San Francisco when it was 80 degrees out, you'd be six psi down by the time you reached Tahoe and the temperature hit 20. Six psi is more than enough to cause noticeable handling differences in a Porsche.