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Discussion Starter · #1 · (Edited)
I have 19 inch RFT (run flat) tires on my new 2020 X3 M40i.
All 4 tires are the Bridgestone DUELER H/P SPORT AS RFT 245/50R19 105H XL tires.
When I ordered my new X3 I had several tires to select from and as the 19 inch tires are the only all-season tires I chose it over the 20 and 21 inch tires as these are only performance tires, not recommended for winter driving. I am also very surprised about BMW tire packages, they should have more than one size in all-seasons.
I live in Colorado where we have cold freezing temperatures and of course snow. So the 19 inch all-seasons were my only logical choice, I did not want to go to the extra added expense and get performance tires (20 or 21 inch tires) and then be forced to buy 4 new all-season tires, plus the inconvenience to swap tires twice a year when the seasons change.
The factory recommended PSI on my driver door jamb is 32 psi for the fronts and 36 psi for the rears. It does not mention extra added weight at all. Sticker picture is below.
I am a little puzzled by this as there is more weight on the front of the car (due to the engine) than the rear, and my rear hatch is always empty, so no extra weight.
Do these PSI numbers look right to you experts?
I have also read on other forums to add +2 PSI on RFT. Do you agree on this?
So ....what should PSI should I put in my tires?
I am quite good in checking these as I check about once a month in the morning when tires are cold as temperatures do vary a lot where I live. For each 10 degrees F temperature change there is 1 PSI change, it increases for warmer temps and decreases for colder temps.
Thanks a lot in advance.
 

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The numbers look fine. The SAVs I've seen all have higher numbers for the rear tires.
Somewhere in the manual there're more numbers (higher) for more passengers, more cargo or higher speeds.
 

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The numbers look fine. The SAVs I've seen all have higher numbers for the rear tires.
Somewhere in the manual there're more numbers (higher) for more passengers, more cargo or higher speeds.
Almost; the tire pressures on the door sill are for maximum pax (5 people), max load (luggage and stuff), and maximum speed (over 100 mph). The alternative pressures (all lower) in the printed book are for lower pax, loads & speeds.

There are pressures also listed in the handbook for alternative approved tire sizes; the pressures on the door sill sticker are only for the tires the X3 was delivered with
 

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I am a little puzzled by this as there is more weight on the front of the car (due to the engine) than the rear,
Actually, the G01 M40 has perfect 50:50 weight distribution unladen :thumbup:
 

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One of the reasons car manufacturers call for less pressure in the front tires is to improve ride quality, particularly for the front seat occupants. The front seat occupants feel a bump from the front axle stronger than from the back axle, because they're closer to the front axle. During a bump on the front axle, the car is pivoting about the rear axle. The front ride height has an up and down motion. The front seat occupants feel that up and down motion, but it is proportional to their distance from the rear axle divided by the wheelbase. This phenomenon is why longer wheelbase cars ride better. It's also why you see very few cab-over heavy trucks on the road anymore. Truck drivers don't like the ride from sitting over the front axle.

That lower front tire pressure is not necessarily optimal for handling or even tire wear.

I precisely maintain my tire pressures over an entire rotation stint (~7k miles), measured at (or adjusted to) the early morning low temperatures. I then precisely measure the depths of all four circumferential channels on all four tires at the end of the rotation stint (when rotating the tires), using a high-resolution digital tread depth gauge. By maintaining the same pressures over an entire rotation stint, I can establish the correlation between pressures and measurable tire wear patterns. By comparing the average of the wear in the two side channels (inside and outside) to the average wear in the two middle channels, I can identify the need for changing the pressures. (Comparing the wear of the inside channels to that of the outside channels identifies alignment problems.)

I ordered Frau Putzer's 2018 X3 xDrive 30i with 19", all-season, non-run-flat tires (non-RFT's). The door jamb decal recommends 32 PSI front, and 35 PSI rear for speeds under 100 MPH. As a first guess, I set the pressures to two PSI over the decal pressures (34 PSI front, 37 PSI rear). But, this resulted in excessive average side channel wear, particularly on the front axle.

So, for the next rotation stint, I increased the pressures to four PSI over the decal pressures (36 PSI front, 39 PSI rear). This resulted in slightly higher average wear in the side channels on the front (0.18/32") and slightly more average wear in the middle channels on the rear (0.16/32"). This suggests that the front tires were slightly underinflated, and the rear tires were slightly overinflated. With tire rotation, this almost perfectly evens out the average middle and average side wear over all four tires.

The Bridgestone Dueler HP Sport A/S non-RFT's came "round shouldered" when new, with 9/32" of tread in the side channels and 10/32" tread in the middle channels. My goal is to slightly increase the average wear in the middle channels so that all four channels on all four tires wear down to 3/32" of depth at the same time. Since the front tires were wearing as if slightly underinflated, I raised their pressure by another two PSI for the current rotation stint. So, I'm now running 38 PSI in the front and 39 PSI in the rear. But, I could really feel that extra two PSI in the front, with lighter steering and a rougher ride.

All cars' spec's call for a small amount of toe-in on the front axle, and on the rear axle if the car has adjustable independent rear suspension. This small amount of toe-in is necessary to maintain stability. It's on the order of one-twentieth to one-tenth of one degree on each wheel. Turning at speed causes the tires to deform and concentrates forces and wear on the side of the tires that are on the outside of the turn (e.g. in a left turn, the right sides of the tires incur more wear). SUV's are heavier than passenger cars, have a higher center of gravity (transferring more of the vehicle's weight to the side on the outside of a turn), and generally have taller tire sidewalls (causing the tire to tuck under more in a turn). (My 535i has 245/40-19 tires, where Frau Putzer's X3 has 245/50-19's.) All of these factors combined would concentrate wear on the outside of an SUV's tires. I've become friends with the service manager at my favorite BMW dealership, BMW of Bubbaville. She said that excessive outside tire wear is common on BMW SUV's.

During the previous rotation stint, the average outside channel wear was 0.27/32" greater than the average inside channel wear. The car/truck is tracking straight and the excessive outside channel wear is fairly evenly distributed over all four tires. (All of my cars have more wear on the right side tires, because I make left turns faster than I make right turns.) So, I'm not going to get an alignment. Instead, I'm going to invert the tires on the rims at around their half-life. This will result in the outside and inside channels wearing down to about 3/32" at the same time. I can do this because these low-performance SUV tires are symmetric. Doing this will extend the life of the tires by about 10k miles, and I should get somewhere around 60k miles out of these OE tires.

The one thing in the data I can't explain is that almost all of the excessive average outside wear occurred in previous rotation stint (10k to 17k miles). That could be because the alignment was knocked out of whack. Or, maybe it's the result of me flicking the car/truck around more lately. I'll revisit this again at the next tire rotation and measurement (24k miles).
 

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Discussion Starter · #8 ·
Thank you all for all your help and input, I appreciate it very much.
I and of course many other readers do learn a lot by coming here and share our experiences and knowledge.
This is a very useful and helpful forum.
Thanks again and wish you all a great new year.
 

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One of the reasons car manufacturers call for less pressure in the front tires is to improve ride quality, particularly for the front seat occupants. The front seat occupants feel a bump from the front axle stronger than from the back axle, because they're closer to the front axle. During a bump on the front axle, the car is pivoting about the rear axle. The front ride height has an up and down motion. The front seat occupants feel that up and down motion, but it is proportional to their distance from the rear axle divided by the wheelbase. This phenomenon is why longer wheelbase cars ride better. It's also why you see very few cab-over heavy trucks on the road anymore. Truck drivers don't like the ride from sitting over the front axle.

That lower front tire pressure is not necessarily optimal for handling or even tire wear.

I precisely maintain my tire pressures over an entire rotation stint (~7k miles), measured at (or adjusted to) the early morning low temperatures. I then precisely measure the depths of all four circumferential channels on all four tires at the end of the rotation stint (when rotating the tires), using a high-resolution digital tread depth gauge. By maintaining the same pressures over an entire rotation stint, I can establish the correlation between pressures and measurable tire wear patterns. By comparing the average of the wear in the two side channels (inside and outside) to the average wear in the two middle channels, I can identify the need for changing the pressures. (Comparing the wear of the inside channels to that of the outside channels identifies alignment problems.)

I ordered Frau Putzer's 2018 X3 xDrive 30i with 19", all-season, non-run-flat tires (non-RFT's). The door jamb decal recommends 32 PSI front, and 35 PSI rear for speeds under 100 MPH. As a first guess, I set the pressures to two PSI over the decal pressures (34 PSI front, 37 PSI rear). But, this resulted in excessive average side channel wear, particularly on the front axle.

So, for the next rotation stint, I increased the pressures to four PSI over the decal pressures (36 PSI front, 39 PSI rear). This resulted in slightly higher average wear in the side channels on the front (0.18/32") and slightly more average wear in the middle channels on the rear (0.16/32"). This suggests that the front tires were slightly underinflated, and the rear tires were slightly overinflated. With tire rotation, this almost perfectly evens out the average middle and average side wear over all four tires.

The Bridgestone Dueler HP Sport A/S non-RFT's came "round shouldered" when new, with 9/32" of tread in the side channels and 10/32" tread in the middle channels. My goal is to slightly increase the average wear in the middle channels so that all four channels on all four tires wear down to 3/32" of depth at the same time. Since the front tires were wearing as if slightly underinflated, I raised their pressure by another two PSI for the current rotation stint. So, I'm now running 38 PSI in the front and 39 PSI in the rear. But, I could really feel that extra two PSI in the front, with lighter steering and a rougher ride.

All cars' spec's call for a small amount of toe-in on the front axle, and on the rear axle if the car has adjustable independent rear suspension. This small amount of toe-in is necessary to maintain stability. It's on the order of one-twentieth to one-tenth of one degree on each wheel. Turning at speed causes the tires to deform and concentrates forces and wear on the side of the tires that are on the outside of the turn (e.g. in a left turn, the right sides of the tires incur more wear). SUV's are heavier than passenger cars, have a higher center of gravity (transferring more of the vehicle's weight to the side on the outside of a turn), and generally have taller tire sidewalls (causing the tire to tuck under more in a turn). (My 535i has 245/40-19 tires, where Frau Putzer's X3 has 245/50-19's.) All of these factors combined would concentrate wear on the outside of an SUV's tires. I've become friends with the service manager at my favorite BMW dealership, BMW of Bubbaville. She said that excessive outside tire wear is common on BMW SUV's.

During the previous rotation stint, the average outside channel wear was 0.27/32" greater than the average inside channel wear. The car/truck is tracking straight and the excessive outside channel wear is fairly evenly distributed over all four tires. (All of my cars have more wear on the right side tires, because I make left turns faster than I make right turns.) So, I'm not going to get an alignment. Instead, I'm going to invert the tires on the rims at around their half-life. This will result in the outside and inside channels wearing down to about 3/32" at the same time. I can do this because these low-performance SUV tires are symmetric. Doing this will extend the life of the tires by about 10k miles, and I should get somewhere around 60k miles out of these OE tires.

The one thing in the data I can't explain is that almost all of the excessive average outside wear occurred in previous rotation stint (10k to 17k miles). That could be because the alignment was knocked out of whack. Or, maybe it's the result of me flicking the car/truck around more lately. I'll revisit this again at the next tire rotation and measurement (24k miles).


I found your extensive detailed analysis the exact information I have been seeking. The physics of the tread depth measurements and the variance of the PSI between front and Rear tires makes total sense. I have noticed that my 19 RF Michelin tires are significantly more worn on the outer tread of both front tires and it seems that the alignment need to be adjusted. However, I am shopping for replacement tires and want to go to a traditional tire but one that is considered a performance product, all season with excellent wet road handling as I live in Florida. I have a 2014 740i with the Sport Drive options. I will NOT have a Bridgestone Tire even if they were free. (old Firestone - they treated me very badly over 40 years ago. I do not forget and I hold a grudge). I am reviewing Michelin, Perelli, Hankook, Yokohama. Will do my research before the investment. Your insights and research have shown me that is the wisest course before buying new shoes for my baby. :cool: P2
 

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Run-flats tend to wear as if they're under inflated. That's because the sidewalls can't stretch as much in the circumferential direction. That circumferential sidewall stretching is why radial tires wear more evenly than bias-ply tires.

I changed my mind and got the X3 aligned shortly after the 17k mile tire rotation. The front toe was out. At the 24k mile rotation the average outer channel wear was only 0.07/32" more than the average inner channel wear. At 24k miles, I also goosed up the pressure to 39 PSI, front and rear.

I've found that (non run flat) Michelins are very sensitive to pressure. It's easy to over inflate them, causing excess center channel wear. But, that means it's also easy to dial them in to a perfect pressure.

"Performance" and "all-season" are usually contradictions. But, Michelin makes a Pilot Sport A/S 4. They're skewed more toward dry performance than snow. Reviews say the dry performance is 10% better than the PS A/S 3+ that it replaces. They also last longer than the summer, ultra-high performance PS 4S.

Frau Putzer's X3 will get some PS A/S 4's after the OE Bridgestones are worn out (60k to 70k miles). We'll be living on a hilltop where it snows by then. So, I'll also buy a dedicated set of snow tires and wheels.

There's a $70 rebate on four Michelins, ending this week.

There's a parts list floating around for converting a 7's trunk to hold a spare tire and jack and still have a flat trunk floor (but raised up about 6").

Going from run--flat Goodyear LS2's to Michelin PSS's transformed my 535i. I got 40k miles out of them, now replaced with PS 4S's.

They didn't make my size in PS A/S 4''s when I bought my PS 4S's. Otherwise, I'd have got the A/S's.

I've improved my "tire whispering" spreadsheet since my post above. Here's the X3's data at the 17k-mle and 24k-mile tire rotations. The 24k-mile data shows that my alignment was $145 well spent. For the current rotation stint, I'm running both the front and rear tires at 39 PSI (measured in the morning). The OE Bridgestones (like most Michelins) came "round shouldered," with 9/32" of tread in the inner and outer channels and 10/32" of tread in the two middle channels. So, a little over inflation will square them up and make the tires last longer.

20200306 bmw g01 x3 tire wear data at 17k miles.jpg
20210124 g01 x3 30i tire wear data at 23932 miles (highlighted) .jpg


Here are the tread pattern of the Michelin PS A/S 4. The outside half (right) of the PS A/S 4's tread is better suited for dry performance, and the inside half (left) of the tread is better suited for rain and snow.

michelin pilot sport a-s 4 tread.png
 

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Run-flats tend to wear as if they're under inflated. That's because the sidewalls can't stretch as much in the circumferential direction. That circumferential sidewall stretching is why radial tires wear more evenly than bias-ply tires.

I changed my mind and got the X3 aligned shortly after the 17k mile tire rotation. The front toe was out. At the 24k mile rotation the average outer channel wear was only 0.07/32" more than the average inner channel wear. At 24k miles, I also goosed up the pressure to 39 PSI, front and rear.

I've found that (non run flat) Michelins are very sensitive to pressure. It's easy to over inflate them, causing excess center channel wear. But, that means it's also easy to dial them in to a perfect pressure.

"Performance" and "all-season" are usually contradictions. But, Michelin makes a Pilot Sport A/S 4. They're skewed more toward dry performance than snow. Reviews say the dry performance is 10% better than the PS A/S 3+ that it replaces. They also last longer than the summer, ultra-high performance PS 4S.

Frau Putzer's X3 will get some PS A/S 4's after the OE Bridgestones are worn out (60k to 70k miles). We'll be living on a hilltop where it snows by then. So, I'll also buy a dedicated set of snow tires and wheels.

There's a $70 rebate on four Michelins, ending this week.

There's a parts list floating around for converting a 7's trunk to hold a spare tire and jack and still have a flat trunk floor (but raised up about 6").

Going from run--flat Goodyear LS2's to Michelin PSS's transformed my 535i. I got 40k miles out of them, now replaced with PS 4S's.

They didn't make my size in PS A/S 4''s when I bought my PS 4S's. Otherwise, I'd have got the A/S's.

I've improved my "tire whispering" spreadsheet since my post above. Here's the X3's data at the 17k-mle and 24k-mile tire rotations. The 24k-mile data shows that my alignment was $145 well spent. For the current rotation stint, I'm running both the front and rear tires at 39 PSI (measured in the morning). The OE Bridgestones (like most Michelins) came "round shouldered," with 9/32" of tread in the inner and outer channels and 10/32" of tread in the two middle channels. So, a little over inflation will square them up and make the tires last longer.

View attachment 1033601 View attachment 1033602

Here are the tread pattern of the Michelin PS A/S 4. The outside half (right) of the PS A/S 4's tread is better suited for dry performance, and the inside half (left) of the tread is better suited for rain and snow.

View attachment 1033604
There cannot be anyone else here that puts so much thought into tire pressures as do you. We are all better for it. Thanks @Autoputzer !!
 

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There cannot be anyone else here that puts so much thought into tire pressures as do you. We are all better for it. Thanks @Autoputzer !!
Thanks, ppointer.

I got a lot of time on my hands these days, and I like playing "outcome manipulation games." Some of these games can have practical benefits.

Race teams dial in their pressures by taking pyrometer readings across the tires right after the car comes into the pits. The hotter areas are carrying more weight. My "tire whispering" process is sort of an ultra-slow-motion version of that, taking six months instead of a few seconds.

One of my motivations for "tire whispering" is that I'm somewhat of a tree hugger. Tires are an environmental disaster, from deforestation to make rubber plantations, toxic tire granules washing off roads and into streams causing fish kills, to disposal of old tires. I'm also... well... umm... a money hugger, and tires are freaking expensive.

My lifespan records for sets of tires are: 79k miles, 74k miles, 70k miles, 70k miles, 68k miles, 64k miles, 60k miles and 60k miles. The 68k miles, 64k miles, and one of the 60k miles sets of tires were high-performance tires, but they were on light cars (Civic and Sentra SE-R's). I can only get about 40k miles out of high-performance tires on BMW's. The 74k mile set of tires was on a full-size pick-up truck.

My service writer at BMW of Bubbaville asked me to please not tell any of her customers that I get 50k+ miles out of tires on BMW's She said they'd be mad... at her.

If anybody wants a copy of my tire whispering spreadsheet, PM me with an e-mail address that takes attachments. I'll do a mass mailing in a few days.
 

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Thanks, ppointer.

I got a lot of time on my hands these days, and I like playing "outcome manipulation games." Some of these games can have practical benefits.

Race teams dial in their pressures by taking pyrometer readings across the tires right after the car comes into the pits. The hotter areas are carrying more weight. My "tire whispering" process is sort of an ultra-slow-motion version of that, taking six months instead of a few seconds.

One of my motivations for "tire whispering" is that I'm somewhat of a tree hugger. Tires are an environmental disaster, from deforestation to make rubber plantations, toxic tire granules washing off roads and into streams causing fish kills, to disposal of old tires. I'm also... well... umm... a money hugger, and tires are freaking expensive.

My lifespan records for sets of tires are: 79k miles, 74k miles, 70k miles, 70k miles, 68k miles, 64k miles, 60k miles and 60k miles. The 68k miles, 64k miles, and one of the 60k miles sets of tires were high-performance tires, but they were on light cars (Civic and Sentra SE-R's). I can only get about 40k miles out of high-performance tires on BMW's. The 74k mile set of tires was on a full-size pick-up truck.

My service writer at BMW of Bubbaville asked me to please not tell any of her customers that I get 50k+ miles out of tires on BMW's She said they'd be mad... at her.

If anybody wants a copy of my tire whispering spreadsheet, PM me with an e-mail address that takes attachments. I'll do a mass mailing in a few days.
I would like a copy of that spreadsheet please. Also, I was curious what elevation you're basing your calculations on? I'm in Florida so I'm assuming that my mileage may vary versus someone who is in Colorado for example.
 

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I would like a copy of that spreadsheet please. Also, I was curious what elevation you're basing your calculations on? I'm in Florida so I'm assuming that my mileage may vary versus someone who is in Colorado for example.
The Bubba Estates subdivision in Bubbaville Beach is about 20 feet above sea level. The first place I lived down here was briefly below sea level during Hurricane Opal. Luckily, I'd moved out a few months before Opal hit.

But, elevation doesn't matter. A lot of people notice that their tire pressures don't vary with drastic changes in altitude. They sometimes incorrectly attribute this to having spent $20 to have their tires filled with nitrogen. The wear patterns corelate to gauge pressure, not absolute pressure. Gauge pressure is the difference between the pressure inside the tire and outside the tire. Absolute pressure is the pressure compared to a perfect vacuum (e.g. outer space). Temperatures generally go down as altitude goes up. The reduction in pressure do to lower temperature tends to cancel out the increase in gauge pressure with increasing altitude that would be seen at a constant temperature.

... eight posts in 17 years. You're a man of few words. I'm honored Send me a personal message, called a "discussion" in the new Bimmerfest format, and include an e-mail address that takes attachments. You can do this by clicking on my "A" at the top of this post. I can't attach Excel files to posts here.
 

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I would like a copy of that spreadsheet please. Also, I was curious what elevation you're basing your calculations on? I'm in Florida so I'm assuming that my mileage may vary versus someone who is in Colorado for example.
It looks like you have to register as a member to get or receive private messages from BF members.
 
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