CORSASCHNELL

I check and adjust tire pressure on all 4 cars every Sunday. My 997 sticker says 37/42 PSI but my Indy shop tells me to lower by 2-4 PSI front and rear and the tire will last 40% longer.

Do you guys stick with factory specifications or do you vary your tire pressure to get desirable results?

Hella-Buggin'

I run 33/37 on my mpss tires.

MICHAELWWW

I do not know much about tires since this is my 1st Porsche but is it normal to need new rear tires after only 18000 miles or did I do something wrong? I have potenzas on the car.
Thanks

Hella-Buggin'

I wish I got 18k out of a set. I averaged about 12k on the last two sets. The fronts last awhile because there's little weight there. The rears hold the weight and driving aggressively in the corners will take its toll.

MICHAELWWW

Thanks, I'll drive faster.

808997

Interesting. My service advisor just recommended that I keep it at least at the recommended pressure 37/44. Explained that since most of the wear is in the inner part of the tire, low pressure would make this worse. I only got about 12k out of my rear Michelin Super Sports but am over 20k on my fronts and still have a good bit of tread. What's the logic of keeping it low to extend tread life?

El Fredo

Are you using air or nitrogen?

MICHAELWWW

That's what I have been told. Mine are worn out on the inside and my neighbor mentioned that was due to low pressure.

mdrums

You are looking at the full load of 4 people and luggage pressure. You car will handle...stick ....better with lower pressures.

Stock 2 people and luggage for 2005-07 997 with 19" is 33/39 for C2S and 37 rear on c4s

Stock 2 people and luggage for 2009+ with 19" is 34/39 for C2S and 37 rear for C4S and GTS

Don't believe the air vs nitrogen crap either. Also have your alignment checked as I bet it's off and you might have too much rear toe for street driving and tire wear on the street.


READ YOUR OWNERS MANUAL...it's your best friend for info like this...enjoy!

jhbrennan

Doesn't matter - 37 psi of air is the same as 37 psi of nitrogen.

Tcc1999

Well put. Considering Air is ~78.084 percent Nitrogen, you'd need some pretty sophisticated measuring and delivery devices to compensate for the slight differences in atomic weight (N=14/O=16) and physical properties of the ~20.946 percent O2 and >1 percent trace gases that you are eliminating if you use N alone.

Edgy01

At one of the longer time Porsche drivers on this forum (since the early 1970s) I believe that Porsche puts a lot of time and effort into the engineering behind their tire placard information.

Let's all start with the assumption that Porsches are designed from the start to be optimal handling machines. Handling is more important than, say, tire life. Some owners want to compromise that handling performance by adjusting their suspension settings to get them added tire life. This is a bit of a false economy because the real reason someone buys a Porsche is to experience the incredible handling of the 911. When you change the suspension settings, or put really cheap tires on your Carrera you might as well be driving a Camry.

Just understand that you will have to forgo some tire life in order to get the incredible handling that presumably you were seeking when you bought a Carrera. If we can't agree to this you might as well sell it. With this assumption behind us, begin with the settings that Porsche engineers settled upon. Get yourself a quality tire gauge (Porsches all used to be delivered with a nice VPO tire pressure gauge until Porsche learned about how to economize...) Use that gauge to set your pressures. (The 997.2 and newer TPMS numbers are fairly accurate--some of the 997.1 ones may/will be off by a constant delta.). The point is, settle on some values and stick to them until you get a feel for what those values translate into when it comes to handling and tire wear. ALWAYS check your pressures when the tires are stone cold. Never adjust them after even a short drive because then what you have is a crap shoot--you have no idea of what the TP really is then.

I have always started with my 997S cabriolet (mostly empty of stuff) at 33 and 39. Your numbers will be different because you may have an AWD or you may have a big passenger in the right seat, or a couple of sacks of concrete mix in the front trunk. The trick is to simply stick to your numbers--do this for the life of your first set of tires. Measure the mileage that you have gotten and determine for yourself if you think that the mileage is poor. For those new to the 911 experience, you will soon discover that you replace these things in a 2:1 ratio--rears to fronts. You will go through twice as many rear tires as you do fronts.

Evaluate your tires by getting on your back. You can no longer just peek under your car from the rear or the sides. You have to get down on the concrete or asphalt and actually look at the inner portion of the tread. This is particularly critical for the rears. Inside wear is perfectly normal to regular new-to-Porsche drivers. It just means that you are not driving it aggressively enough yet. I don't expect you to get the hang of driving these things that quickly. They can be very tricky. Your goal is to scrub your outer edges in an effort to keep up with the inner wear due to the high negative camber that Porsche recommends for optimal handling.

Years ago, when we first began to learn about low profile tires (like the Pirelli P7) we were all concerned about why we had wear in the centers. If you are not set up with the right pressures you could be either under inflating, or over inflating. When under inflating the centers of the tires would flex into the ground and be negatively affected by centrifugal force. If over inflated the centers would wear from centrifugal force by being forced into the ground--the same results, but obtained differently. You would always have to aim for the centroid values to optimize tire wear.

The bottom line is to check your pressures and keep them at a particular value to the best of your ability--and then evaluate them at tire checking time. If you're not happy with the mileage try something different. If over inflated, these things tend to be very harsh. Also, don't be too judgmental of your tires if they are dried out from many many heat cycles. That's no way to judge a tire. Give them the benefit of the doubt. If you have bought a Porsche used, and are unsure of the dryness of the tires on the car, do yourself a favor and spring for a new sets of rubber--all around. Don't be frugal here. You will be paid back in spades.

Forget the nitrogen versus air debate. Aircraft operators chose to run nitrogen in their tires because at altitude the tires will get cold--like minus 30-40 degrees, and any moisture (which normally is found in 'air') will freeze and possibly cause you issues, whereas nitrogen is bottled for distribution with no moisture to freeze up inside an aircraft tire. Forget the stuff about the molecular structure of nitrogen vice air. Remember, air is essentially 79% nitrogen to start with. (Do you really think they put the tire in a 100% nitrogen ROOM to mount the tire in the first place to ensure that only NITROGEN is in the tire?)

GSIRM3

I only use German air in my tires, and I rotate the air quarterly.

CORSASCHNELL

A question: The sticker on the driver side door with the tire pressure info, has 997.701.287.51, on my car.

What does it mean? Thanks.

Mumbles

I strictly use helium, better gas mileage