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Discussion Starter #1
hello there i recently installed 4 sets of micheline non run flat pilot sport 4s the recomended cold tire pressure on label on side of the door says for low load 2 people maximum
225/40/19 : 2.4 bar(35psi)
255/35/19: 2.7 bar (39psi)
and for full load 4 people + stuff in trunk
225/40/19: 2.8 bar (40psi)
255/35/19: 3.3 bar (48 psi)

both seem very high to me on my other cars maximum pressure is cold 35 and these recomended looks weird what pressure should i use based on the information i gave?
and i asked a tireshop and they said the label information is not trustable put all on 32psi but i dont think he is being legit
 

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32 psi on 19's is an expensive gamble. Also, remember the pressure on door panel is for RFTs. I would rec you start with door panel rec (but no lower) and see how the softer non-RFTs feel. Most will recommend about 2 psi above the recommended RFT pressure
 

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It's been my experience that high-performance Michelin's need less pressure to wear evenly than high-performance Goodyear's or Continental's. Tire pressure varies with temperature, going up about one PSI for every ten degrees F. So, it's good to define pressure as that in the early morning, when the car is completely cold, the outside temperature is the lowest of the day, and sunlight has not hit the tires yet and heated them.

The "normal" decal pressures or even 5% over, measured early in the morning, are a good first guess. That's pretty much what eddymerckx3 said. He's also right that low-profile tires need a lot of pressure compared to "regular" tires.

From a first guess at pressures, you can "dial in" the correct pressure by periodically measuring the tread depths in all four channels in each tire. You'll need to use the same pressure for several thousand miles to get measurable wear that you can corelate to a specific pressure. I measure tread depths and change my baseline pressures when I rotate the tires (~5k to 8k miles). But, since you have a staggered set up, you cannot rotate your tires front to back.

The second best tread depth gauge is just a simple mechanical one they sell in any auto parts store. The graduated markings are in 32nds inch or mm. But, you can eyeball the measurements to a 1/2 or a 1/4 of a 32nd inch or mm. That resolution is necessary to identify wear patterns vs. pressures. The best tread depth gauge would be a machinist's depth gauge.

I built an Excel spreadsheet for crunching the raw tread depth data and then calculate wear in each channel on each tire, and the averages on each tire, each axle, each channel. From this data, I can see what pressure changes I need to make, and also if I have an alignment problem.

I overestimated the pressures needed in my PSS's when I got them. This was based on the very high pressures I needed to get my OE RFT Goodyear's to wear evenly. Here's a snapshot of my spreadsheet at 45k miles (14k miles on the tires) showing that I had excessive wear in the centers of the rear tires (indicative of too much pressure). Also, here's a snapshot of my spreadsheet at 51k miles (20k miles on the tires) showing that the pothole I hit a few thousand miles earlier knocked my car out of alignment, causing excessive wear on the outer channel of three of my tires and slightly elevated inner channel wear on the fourth tire. The car still tracked straight. But, the spreadsheet data showed that I needed an alignment. Alignments are much cheaper than tires.

My decal for my F10 535i square set-up says 35 PSI front and 39 PSI rear. I'm currently running my PSS's at 38 PSI front and 40 PSI rear. Although, I might lower the rear pressure 2 PSI for the next rotation stint. Your car is lighter than mine. Also, I've found that the wider the tire, the less pressure it requires. I had 225's on front and 255's on the back of my E46 M3. I had to go way below the decal pressures on the rear to get the Michelin PS's to even come close to wearing evenly. I went through three sets of rear tires and they all wore excessively in the middle. Here's a cheat sheet of the causes of uneven tread wear patterns.

From rotating (on a square set-up), watching the wear patterns closely, and by gradually dialing in the proper pressures for my tires to achieve even wear, I'll get 40k miles out of my PSS's, on my 4100 pound 535i.

Think real hard about getting a mini-spare and jack kit for your car. It will take up the trunk, but it can also save you a load of grief if you have a flat. You'd have to carry the flat tire in the back seat. So, carrying a necessary bag (disposable or reusable) will save trashing your interior.
 

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32 psi on 19's is an expensive gamble. Also, remember the pressure on door panel is for RFTs. I would rec you start with door panel rec (but no lower) and see how the softer non-RFTs feel. Most will recommend about 2 psi above the recommended RFT pressure
A good starting point. I like 3 psi more on my car.
 

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Discussion Starter #5
update:
i put cold temps front 2.4 bar and rear 2.7 bar and the steering feels softer and the front tires are not very accuret these pressures are higher than before so feels like the highe rit goes the less responsive it becomes
 

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I have now 4 new ps4's for about 4 weeks now, 19" 225 front 255 rear and i stick to the 2.6 bar front and rear, same as with the bridgestone s001 runflats before. seems ok

garage first wanted to pressure them at 2.4 bar, i said nono :tsk:
The first pothole at some speed would damage my rims.

when i'm driving away they are cold at 2.4 bar (6° C here)

Very good tires by the way, low noise, loads of grip.
and the whining noise i got for some time with the RFT's went away.
 
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