[fullsmoke]

Hello,

Since the weather got cooler, my 21 M5 is saying my tires need more pressure. Looks like the computer wants 38 psi front and 39 psi rear. This is odd to me as the door sill sticker says 32/33. These are Michelin pilot sport 4s 275/285. Is the computer correct in wanting 38/39? Is this because of temperature change?

Thanks,
FS

[pbonsalb]

At 38/39 psi, the center of my rear tires wears more than the edges. That is usually a sign of overinflation. Has anyone else seen this? I run more like 33/34, which is the light load comfort setting.

[NoMods]

It will vary iirc from the weather and it makes recommendations.

[DarkishM5C]

Here's some info from my '23 owner's manual. Depending on the speeds (up to 100 mph or over 100 mph) that you will be driving and whether you have the M 'Drive package, will depend on what psi to set your tires.

[Aronis]

I have mine at 44 and 45......above 100 mph frequently. LOL

Mike

[shawnhayes]

Originally Posted by Aronis

I have mine at 44 and 45......above 100 mph frequently. LOL

Mike

These get awfully squirrly when hot above 40. How's that handling?

Shawn

[pbonsalb]

BMWs high psi recommendations are for fully loaded weight autobahn use where the 100+ is sustained and handling is not the goal. For the occasional highway pull you don’t need to set your tires at 45 psi cold. Can’t go 100+ for long in my area of the US.

[Maverik259]

Originally Posted by fullsmoke

Hello,

Since the weather got cooler, my 21 M5 is saying my tires need more pressure. Looks like the computer wants 38 psi front and 39 psi rear. This is odd to me as the door sill sticker says 32/33. These are Michelin pilot sport 4s 275/285. Is the computer correct in wanting 38/39? Is this because of temperature change?

Thanks,
FS

I think the response have missed the point of the question. First why do you think the computer wants 38-39 psi?

Correct psi is on the door 32/33. However in cold this can easily drop into the 20s and you get a warning. So in the winter I run cold pressures around 35/36 to preclude this. I usually won't reach full operating temps by the time I get to work but if I do it's still velow 40. I've found anything above 40 leads to an awful rough ride.

[shawnhayes]

Originally Posted by Maverik259

I think the response have missed the point of the question. First why do you think the computer wants 38-39 psi?

Correct psi is on the door 32/33. However in cold this can easily drop into the 20s and you get a warning. So in the winter I run cold pressures around 35/36 to preclude this. I usually won't reach full operating temps by the time I get to work but if I do it's still velow 40. I've found anything above 40 leads to an awful rough ride.

We're all betting that you have the computer set to > 100 mph for the tire setting.

I personally ignore the shit out of the computer warning when I'm on track. The stupid thing squawks when I start out at 27 psi in the shittiest hot day in July on track and is still reporting "low tire pressure" when the tires ALL THE WAY ROUND read 39 psi. It's just a suggestion. Personally, for you, I'd set the psi cold at 32/33 JUST LIKE ON THE DOOR. Make sure the computer is set for the proper tire and < 100mph. TPMS's are for the really dangerous pressures of 20 in a fully loaded SUV. It's what they're for. For the people like us, they don't do much other than make us more aware.

Shawn

[Greer]

I usually run 33/34 and I get great handling.

[rccarps2]

Originally Posted by Greer

I usually run 33/34 and I get great handling.

Same here. My sensors just went off a few days ago. Fronts were around 27 and the rears 29. Pumped them up to 33/34. Almost time for the winter swap anyways.

[fullsmoke]

You guys are right! Computer was set for >100. Such a simple fix—no way was I going to inflate tires to 38/39!

[Aronis]

Originally Posted by shawnhayes

These get awfully squirrly when hot above 40. How's that handling?

Shawn

Dude, just kidding.....I never exceed the posted speed limit, never.

I have them set as per the display 36 front, 37 rear......

I had been putting them at 42, all around for years, never noticed any handling issues. I find infact the cars handle more crisply at higher pressures. But since this thing tells me 36/37, that is where I try to keep it. Just checked, I'm at about 32/33 now, so have to add some air.

Mike

[shawnhayes]

Originally Posted by rccarps2

Same here. My sensors just went off a few days ago. Fronts were around 27 and the rears 29. Pumped them up to 33/34. Almost time for the winter swap anyways.

In PA? Really? Temps in VA (not that far south of you), the summer tire temps aren't reached reliably until November/December. Hmm. I guess that isn't that far away, though. Time passes fast.

Shawn

[shawnhayes]

Originally Posted by fullsmoke

You guys are right! Computer was set for >100. Such a simple fix—no way was I going to inflate tires to 38/39!

Good call. But, if you ARE going to run on the autobahn in the summer for more than a few miles, those high pressures give more air to absorb the heat. That's why that setting is there (I guess there is Montana as well).

Shawn

[shawnhayes]

Originally Posted by Aronis

Dude, just kidding.....I never exceed the posted speed limit, never.

I have them set as per the display 36 front, 37 rear......

I had been putting them at 42, all around for years, never noticed any handling issues. I find infact the cars handle more crisply at higher pressures. But since this thing tells me 36/37, that is where I try to keep it. Just checked, I'm at about 32/33 now, so have to add some air.

Mike

It depends on what you call "crisper" I guess. At less than 0.5g, I would say you are right. Turn in will be a little quicker.

As the speed, and the g's increase, ANYWHERE near 40 psi gets squirrely on most street tires (even on hot pressures). The excess air keeps the tire from "working as designed". Most manufacturers have an "optimal" road pressure. This is usually achieved after about 20 minutes of driving on a car in 70 degree weather with the tire at the recommended cold pressure of the car (almost always 32 psi, unless you're talking about a weirdo like the i3 - I had two of them). Almost every other condition becomes a compromise.

https://www.firestonecompleteautocar...ate-car-tires/

On the track, trackrats like I am, almost always note that anything DOT legal starts to slide at anything over 40 psi. Hot or cold. Despite physics (which doesn't give a shit about size of contact patch), real cars have "rollover" on tires. As the car corners, the tires roll over onto the outside edges of the tire (on the outside of the turn radius). The inner tires roll over on the inside edge. Traction seems to be compromised. Physics says that as long as the friction coefficient doesn't change, it shouldn't matter. But it DOES. Otherwise, we'd all have bicycle tires on our cars.

I'm sure the reasons are more complicated, but both car and tire manufacturers agree. Inflate to recommended pressures and stay there.

Shawn

[Danny D]

I set them ALL at 33 PSI cold. Period.

[rccarps2]

Originally Posted by shawnhayes

In PA? Really? Temps in VA (not that far south of you), the summer tire temps aren't reached reliably until November/December. Hmm. I guess that isn't that far away, though. Time passes fast.

Shawn

It comes up quick. Hitting the upper 40s at night for most of next week.

Car goes in for service/inspection/emissions in a few weeks. Plan to swap the tires to my all seasons shortly after.

[shawnhayes]

Originally Posted by rccarps2

It comes up quick. Hitting the upper 40s at night for most of next week.

Car goes in for service/inspection/emissions in a few weeks. Plan to swap the tires to my all seasons shortly after.

Originally Posted by rccarps2

It comes up quick. Hitting the upper 40s at night for most of next week.

Car goes in for service/inspection/emissions in a few weeks. Plan to swap the tires to my all seasons shortly after.

I thought you meant actual winters. (Mud and snow) like blizzaks. All seasons are meh.

Shawn

[rccarps2]

Originally Posted by shawnhayes

I thought you meant actual winters. (Mud and snow) like blizzaks. All seasons are meh.

Shawn

I got A/S that I can swap on the stock wheels. $100 in the fall and again in the spring for someone to come to my office and do it in the parking lot. If the weather is nasty, I will just use the X7 that sits at home.

I don't drive the M5 in standing snow. So don't need the snow tires. A/S's suit my needs for the colder winter temps.

[bruza]

Timely post, I just had my PS4s installed Thursday. I was surprised when they set my new tires at 34 PSI cold.

I usually run a couple lbs less but after seeing this thread I’ll stay at 34.

Goes w/o saying, PS4s >>> P ZERO’s

[shawnhayes]

Originally Posted by bruza

Timely post, I just had my PS4s installed Thursday. I was surprised when they set my new tires at 34 PSI cold.

I usually run a couple lbs less but after seeing this thread I’ll stay at 34.

Goes w/o saying, PS4s >>> P ZERO’s

If this is a daily, yeah, that's perfect.

Shawn