My trusted tire store says the fronts are okay but the rears are marginal tread-wise. They're the Michelin PS4S's, all about six years old.
I have a 2500 mile trip coming up in about a month and am thinking I might replace only the rears now and maybe the fronts afterward. Is there any "rule" against replacing these tires in pairs rather than as full sets? (The upcoming trip is mostly highway miles and no weather stresses). Thanks.

 

I've done the rears only without any issue.

But I do like the feel of all 4 new at the same time.

 

It's no issue. The tires should all be the same type/brand though.

 

The rears typically wear out twice as fast as the fronts. It is normal to replace the rears only (using same brand and model tires as on the front) once then on the next rear change to do all four. I was considering changing from P-Zeros to Michelin but need to wait until all four are changed together so it was one more set of rear P-Zeros before I can consider the switch on the next all four change. Basically based on my driving mileage a set or rears every year and a set of all four every other year. Give or take.

 

My experience has been "2 for 1" - twice the longevity on the front versus the rear. Keep with the same tire manufacturer and style.

 

I was in the same spot last summer on a long road trip, long. Had a flat on a rear P-Zero. I will change the rears, but never just one. The other was not in bad shape, but replaced it anyway. No issues for the remaining 6K miles on the trip. The Pirelli’s have been much better than expected, but considering the P4S or DWS06+ next time I can change all four.

 

Replaced rears only on my T a few years ago due to a nail in one. No issues.

 

6 year old tires? You should replace all of them. Car manufacturers generally recommend replacing tires after 6 years, regardless of tread depth. Depending on how long they sat before being installed on the car, they may even be considerably older than 6 years.

 

I've gone through 3 sets of rears and my fronts are still at 70% in that time. So I only change the rears, on pirellis, but waiting for the front to require change so I can try the Michelins on all 4. I go through a set of rears per year.

 

I'm the OP here and based on the posts above I've decided to replace the rears only (with the same PS4S's). I didn't realize that the rears seem to wear considerably faster than the fronts so it's common to replace rears only.

 

Is this still true for the AWS models?

 

Yes I believe it is as the power to the front wheels is only sent there as needed and regulated by the computer in normal driving (no in launch control). Also in a rear engine Porsche, the weight and massive amounts of torque will always cause faster wear at the rear wheels. The very reason a Porsche punches above its HP in acceleration and grip, is due to it's ability to put the traction and torque forces to the pavement via the rear wheels. Feel free to correct me if I am wrong about this as I have 2WD but my buddy's 4S wears rears about the same as mine. Whether or not the rears are completely worn out I would tend to replace the rears when the fronts get to 50% even if the rears have a little life left. At least that way every other time I can put a new fresh set of four on. I try to manage my tires so that a new set of rears goes on with at least half the life left in fronts. I could sometimes get a little more out of the rears but then you can be faced with fronts getting too low with too much life left on the rears. Otherwise you are always driving on a couple of tires with substantially less tread.

 

I’ve done this many times on all my RWD cars. For me, the rears only last about half as long as the fronts so it works out okay. I tend to accelerate briskly lol.

 

Its common for people who drive fast in a straight line to go through rears faster as they spin the wheels more often.

Guys who actually drive their car hard through corners wear at similar rates front to rear.

if you’re a commuter, it doesn’t matter what you do.
Yes, if you get more than 2 years from a set of tyres on a 911 you are a commuter.

Someone letting you drive a 911 on 6 year old tyres is not someone I would trust.

 

oh? haven't been to the track in a hot minute but if memory serves, the 911 will still burn the rears faster than the fronts unless you're sliding in turns.

it's perfectly okay to commute in a 911.