[dmicah]

On the way down to Palm Springs I noticed that brief spurts of speed from 85-95 would trigger a "TPMS malfunction." Usually it would clear. I have the 20" staggered setup with Michelin Pilot Sport A/S 3+ that are W or Y rated (can't recall). I had set the TPMS system to Winter/All Season, speeds <100. I reset it to >100 and the malfunctions stopped coming, but then the car started complaining about my tires being under-inflated ("Driving still possible"). The recommended pressures were uncomfortably high so I ignored them.

I guess I have two questions:

1. Anybody else have something like this happen?
2. Is the speed setting in TPMS meant to reflect the speed capabilities of the tire or the speeds you intend to drive?

[TheusBimmer]

[*]Is the speed setting in TPMS meant to reflect the speed capabilities of the tire or the speeds you intend to drive?[/LIST][/QUOTE]

The speed setting in TPMS to be configured on iDrive is meant to reflect speed capabilities. The letter at the end of your tire load will reflect your tire speed. e.g. on my winter tires Pirelli Sottozero square setup, the size of tires are 245/50R19 105V XL, of which 105 is the tire's load index, and V is the tire's speed rating. If you go down the table below I provided you (source: tirerack.com), a V speed rating allows me to go up to a max speed of 149mph. So when I change from summer to winter tires, I go back in idrive setting for my tires, select the size of winter tires and select >100mph.

If your winter tire has a speed rating of Q, then you should set it up at <100mph for your and everyone's benefit. And shouldn't go faster than established speed rating unless want to cause some potential sort of accident.

Per Tirerack
"Speed ratings were established to match the speed capability of tires with the top speed capability of the vehicles to which they are applied.
Speed ratings are established in kilometers per hour and subsequently converted to miles per hour (which explains why speed ratings appear established at "unusual" mile per hour increments).
Despite the tire manufacturers' ability to manufacture tires capable of high speeds, none of them recommend the use of their products in excess of legal speed limits.
The maximum operating speed of a vehicle must be limited to the lowest speed rated tire on the vehicle."

https://www.tirerack.com/tires/tiret....jsp?techid=35

L 75 mph 120 km/h Off-Road & Light Truck Tires
M 81 mph 130 km/h Temporary Spare Tires
N 87 mph 140km/h
P 93 mph 150 km/h
Q 99 mph 160 km/h Studless & Studdable Winter Tires
R 106 mph 170 km/h H.D. Light Truck Tires
S 112 mph 180 km/h Family Sedans & Vans
T 118 mph 190 km/h Family Sedans & Vans
U 124 mph 200 km/h
H 130 mph 210 km/h Sport Sedans & Coupes
V 149 mph 240 km/h Sport Sedans, Coupes & Sports Cars
W 168 mph 270 km/h Exotic Sports Cars
Y 186 mph 300 km/h Exotic Sports Cars

[TheusBimmer]

1. Anybody else have something like this happen?

[/QUOTE]

I wonder if you actually went above the 100mph and therefore it gave you a warning related to TPMS?

Never happened to me as I put my setting at >100mph.

Also, iDrive recommends higher PSI if going at higher speeds. Need to look into why that's the case, but from a physics standpoint seems logical though not sure if related to air pressure, contact of tires at elevated speed etc.

[dmicah]

Originally Posted by TheusBimmer

The speed setting in TPMS to be configured on iDrive is meant to reflect speed capabilities. The letter at the end of your tire load will reflect your tire speed.

Thanks for your response. That's what I thought as well, but here's the manual on this topic:

Tire inflation pressures at max. speeds above 100 mph/160 km/h

Warning
In order to drive at maximum speeds in excessof 100 mph/160 km/h, please observe, and, if necessary, adjust tire pressures for speeds exceeding 100 mph/160 km/h from the relevant table on the following pages. Otherwise, tire
damage and accidents could occur.

For speeds over 100 mph/160 km/h and for optimum driving comfort, note the pressure values in the tire inflation pressure table, refer to page 291, and adjust as necessary.

That kinda sounds like "hey if you intend to go above 100, pump it up." Here in Palm Springs, temps are hitting the mid 100's. If I read the tire pressure table correctly, I'm meant to put the pressures to 39 up front and 45 in the back. That feels high. The max rated pressure of the tire is 50 psi. My A/S 3+'s are Y rated.

Are you running similar pressures, since you've set it to +100?

Originally Posted by TheusBimmer

I wonder if you actually went above the 100mph and therefore it gave you a warning related to TPMS?

Never happened to me as I put my setting at >100mph.

Also, iDrive recommends higher PSI if going at higher speeds. Need to look into why that's the case, but from a physics standpoint seems logical though not sure if related to air pressure, contact of tires at elevated speed etc.

It's possible, but I'm pretty sure we never beat 93 MPH. Again, I'm curious as to what pressures you've chosen and whether you feel they've affected ride comfort.

[TheusBimmer]

Originally Posted by dmicah

Thanks for your response. That's what I thought as well, but here's the manual on this topic:

Tire inflation pressures at max. speeds above 100 mph/160 km/h

Warning
In order to drive at maximum speeds in excessof 100 mph/160 km/h, please observe, and, if necessary, adjust tire pressures for speeds exceeding 100 mph/160 km/h from the relevant table on the following pages. Otherwise, tire
damage and accidents could occur.

For speeds over 100 mph/160 km/h and for optimum driving comfort, note the pressure values in the tire inflation pressure table, refer to page 291, and adjust as necessary.

That kinda sounds like "hey if you intend to go above 100, pump it up." Here in Palm Springs, temps are hitting the mid 100's. If I read the tire pressure table correctly, I'm meant to put the pressures to 39 up front and 45 in the back. That feels high. The max rated pressure of the tire is 50 psi. My A/S 3+'s are Y rated.

Are you running similar pressures, since you've set it to +100?

It's possible, but I'm pretty sure we never beat 93 MPH. Again, I'm curious as to what pressures you've chosen and whether you feel they've affected ride comfort.

Originally bmw dealership had mounted my winter tires this past december and they had it set up I believe at <100mph. I did not like the drive at all as it felt sagging and simply heavy. I changed the setting to >100mph as I was planning to go over the 100mph on the italian highways, so I changed the setting in iDrive, and I was then prompted to jack up the pressure by about 5psi. So I went with the recommended psi on cold tires by iDrive (1psi lower than recommended by iDrive), and lo and behold, the car drove the way I like it: supple and firm ride. Not as good as my summer 21" but close enough (I have standard M suspensions and really enjoy the overall firmness).

So I ended up putting 36psi in front and 40psi in the back, 1psi less than recommended by idrive, which has been working well on my trip in Italy. I say try to increase psi based on idrive recommended and see how you like it (on cold tires). I drove about 1k kms with the higher psi and have not noticed any difference in wear on tires, though perhaps I should be rotating them soon before heading back north. Mind you mine are winter directionals, so only one way swap.

Edit: re-reading your post in my iphone and I am a bit surprised at the high psi idive is recommending you. I thought in general you pumped more air during winter time? Perhaps due to bigger wheels? Doesn't add up. Are the 45psi recommended when your rears tires are cold?