[QUOTE=wanderfalke;4140337]High heat usually, caused by high speeds. Plus tires can "chunk" meaning bits break off. Tires also blister and cup in the tread blocks and when so those "out of round" bits wear differently than the rest of the tire.

 

My only nitpick with the MPSS is that they don't seem to have as high a cornering limit as the OEMs. I live off of one of the premier driving roads in socal so I have a fairly fine sense of handling limits. I virtually never broke the Pirellis loose like I can with the MPSS on my daily drive.

I'm running std pressure/full load (ie, 36/44) for a couple of reasons. First, that is the pressure that the factory set when I took delivery in Zuffenhausen; and second, I tend to prematurely wear the outside edge of tires on every vehicle I've owned unless they are set to the upper range of of rec pressures. Even wear, tread life, and handling are more important to me than comfort.

Never heard that MPSS work better with lower pressures, and they do fine on my 650 at higher than normal pressures. Maybe I'll give lower pressures a try on the 991.

Spyder

 

Try 31/34. I think you will be very pleased.

 

Until you hit a sharp bump and bend the wheel. Truly I wouldn't ever go less than a few PSI under recommended as handling, cornering and braking may suffer. The point is to let the suspension handle road irregularities, not the tires. The right tire pressure keeps the contact patch and deflection correct for the car design. Too less and during aggressive cornering you may actually put some of the sidewall in contact with the ground. But just for a second until the tire rolls off the rim

 

If you take a look at your manual you will find that these are the recommended "comfort" pressures for winter tires (31/39 for summer tires on a CS2 with 20" wheels). There is no risk of the tire rolling off the rim but Porsche recommends keeping the speeds below 150mph at this pressure. In addition I know from personal experience that the MPSS do not grip well over 40psi whereas the P0s are less sensitive to higher pressures.

If Spyder's cold temps are 36/44 and hot temps are 3-5 psi higher, it is no surprise that he feels less grip than from the P0s. In addition, as the max pressure according to Michelin is 50 psi, he is probably more at risk for a blowout with those pressures than rolling off the rim at 31/34.

If you have lots of potholes where you drive than I would try 3-4 psi higher, but if you want maximum grip from the MPSS then hot pressures should be less than 40. And at 31/34 or a few psi more you will be fine, but will want to reset the TPM to comfort. Hot temps will probably be 3-5 psi higher on the street and 8-10 psi higher on the track. I have pulled a over 1.3G lateral and 1.2G under braking routinely at these pressures with no problems including minimal outside shoulder wear (SPASM but no PDCC)

With that said, only do what you are comfortable doing.

 

Johns991 is right;
Use Comfort Pressure w/o Full Load for 20" Summer Tires.
That gives you the low [31/34] pressure you need for PSS to work properly.
This pressure is fully factory recommended.

Part Load is how most people use a 911, so the Full Load setting is overkill.

 

What? You recommend reading manuals and facts over faith? No wonder you are under such cornering pressures!

 

LMAO, yeah go figure. Amazing what you can learn with that interweb thing everybody is talking about.

 

So what is the consensus for optimal tire pressure for maximum wear out? (as opposed to maximum tire performance)?

 

Because a winter tire's character is so different from a summer tire I don't see the logic to apply winter tire pressures to summer tires. Winter tires are much softer rubber, and need the extra deflection to generate the sufficient heat needed in order to grip cold tarmac. In 2 sets of MPSS I tried many lower ranges of PSI and didn't find any real advantage, although consistently used cold pressures as much as 3 PSI lower f/r in an attempt to get more heat in the tire. In the end, it doesn't hurt to trust Michelin's engineers and they recommend 36/44 for a 991 S with 20" wheels on MPSS tires. You won't find this in your owner's manual, but alas on the internet. My P Zero's at -3 PSI (or at the comfort setting) grip far better than both sets of MPSS I had. I'm just hoping the grip lasts over the life of the tire. We'll see.