[arentz07]

Originally Posted by Gaviatrix

My BMW dealer recommended 38 psi rather than the 39 psi (cold, static) which is on the placard for my car (staggered 19" setup). I queried this and they said it was the BMW Australia recommendation for local conditions. To be honest I'm not sure that 1 psi makes any real difference.

It interests me that BMW don't specify any change for load or speed. My Jaguar and the family Subaru both have quite different ratings on the placard for heavy load, towing or high speed. I assume BMW just think you'll be going fast all the time ....

In the iDrive settings, you can change a particular option for traveling at speeds of over 100 MPH, which will affect the recommended pressures shown.

[Gaviatrix]

Originally Posted by arentz07

In the iDrive settings, you can change a particular option for traveling at speeds of over 100 MPH, which will affect the recommended pressures shown.

Thanks - regrettably academic for me in this nanny state where being clocked travelling at 160 km/h+ would likely see me in gaol and my car crushed ...

[4WDFAN]

Originally Posted by Sam Tango

OK. I will add to the confusion: I have a 2023 m340i xdrive, with square Pirelli run-flat all season tires. The door jam indicates 39psi front, 44psi rear.

To me, this is insanely high. At the recommended pressure the car rides very stiff, I feel everything on the road.

Am I the only one with such high recommended tire pressure? I want to lower it to improve ride, but not sure how much I can get away with.

Posts 4 and 5 in this thread may give you an idea of the range of tire preassures, although the data may be for 330i.

I am surprised that the difference between ECO and regular preassures is so big, over 20% for the same load in some cases. I think this would adversely affect handling and lead to premature tire wear. But my experience is with regular tires. Are run-flats more tolerant in this respect?

[Sam Tango]

Originally Posted by Sam Tango

OK. I will add to the confusion: I have a 2023 m340i xdrive, with square Pirelli run-flat all season tires. The door jam indicates 39psi front, 44psi rear.

To me, this is insanely high. At the recommended pressure the car rides very stiff, I feel everything on the road.

Am I the only one with such high recommended tire pressure? I want to lower it to improve ride, but not sure how much I can get away with.

Dealer put 38psi on all four tires when I bought the car (despite what it says on the door jam). I have been driving the car like that for at least 1000 miles.

I just checked the tread depth on the tires, and the shoulders have less depth compared to center.

So, the tires clearly want higher pressure. The door jam also recommends significantly higher than 38psi.

I will go with what the door jam recommends.

[GTF]

Originally Posted by Sam Tango

OK. I will add to the confusion: I have a 2023 m340i xdrive, with square Pirelli run-flat all season tires. The door jam indicates 39psi front, 44psi rear.

To me, this is insanely high. At the recommended pressure the car rides very stiff, I feel everything on the road.

Am I the only one with such high recommended tire pressure? I want to lower it to improve ride, but not sure how much I can get away with.

Additional confusion....I have '21 M340ix w/same tire setup and door jam says 38 F, 42 R! Why the difference? And since weight is roughly 50/50, why ANY difference F to R? I'm assuming the recommendation is with full load, which (for me) is about 0% of the time. I'm at 38 all.

[zazzau]

Originally Posted by GTF

Additional confusion....I have '21 M340ix w/same tire setup and door jam says 38 F, 42 R! Why the difference? And since weight is roughly 50/50, why ANY difference F to R? I'm assuming the recommendation is with full load, which (for me) is about 0% of the time. I'm at 38 all.

I have a M340xi staggered setup and door jam calls for 38 all round but I have mine at 39f/42r and I’m a solo driver most of the time. My tires are wearing evenly — have been for over 2 years.

[Sam Tango]

Originally Posted by GTF

Additional confusion....I have '21 M340ix w/same tire setup and door jam says 38 F, 42 R! Why the difference? And since weight is roughly 50/50, why ANY difference F to R? I'm assuming the recommendation is with full load, which (for me) is about 0% of the time. I'm at 38 all.

the front tires get more hot due to proximity to engine, maybe they are trying to get the pressures equal during driving

[Gaviatrix]

Originally Posted by Sam Tango

the front tires get more hot due to proximity to engine, maybe they are trying to get the pressures equal during driving

Proximity to the engine is unlikely to make any difference whatever to the tyres. The heat build-up in them comes from contact with the road. Additional weight over one axle will affect that - when towing a heavy trailer over long distances with my Land Rover, for example, I would have to increase the rear pressures by about 8 psi to keep the tyres at the same temperature all round. When you're moving, they will be cooled by airflow to a similar extent front and rear. But I don't think I've ever had a car - even FWD - that recommended a higher pressure for the front, even though on many cars 60%+ of the weight is over the front wheels.

[4WDFAN]

Originally Posted by Gaviatrix

But I don't think I've ever had a car - even FWD - that recommended a higher pressure for the front, even though on many cars 60%+ of the weight is over the front wheels.

Looks like you never had a Japanese car https://www.carsguide.com.au/honda/civic/tyre-pressure

[Gaviatrix]

Originally Posted by 4WDFAN

Looks like you never had a Japanese car https://www.carsguide.com.au/honda/civic/tyre-pressure

I've had a few Japanese made cars out of the 40+ cars I've owned, but I don't remember them having higher front pressures. Maybe I'm just getting fuzzy with age. I've only once owned a Honda and that was a motorcycle ...

[HighlandPete]

Originally Posted by GTF

Additional confusion....I have '21 M340ix w/same tire setup and door jam says 38 F, 42 R! Why the difference? And since weight is roughly 50/50, why ANY difference F to R? I'm assuming the recommendation is with full load, which (for me) is about 0% of the time. I'm at 38 all.

Can be as simple as 'tweaking' the handling balance and steering feel. Weight (load carrying), is only one factor in recommended pressure settings.

[Suck9o]

I filled my winter tires to the cold/static pressures in door (32 & 35 psi) and changed the tire settings from summer to winter.

[toddwalton]

Not only does the sticker on the door jamb and the BMW App both recommend different cold tire inflation levels, but so too does the iDrive system. Good job, BMW.

So I've got 3 different sets of numbers. Can anyone let me know which one is the one to follow?

[jg4c]

Originally Posted by toddwalton

Not only does the sticker on the door jamb and the BMW App both recommend different cold tire inflation levels, but so too does the iDrive system. Good job, BMW.

So I've got 3 different sets of numbers. Can anyone let me know which one is the one to follow?

Door Jamb, tried and true. Obviously, cold only.
I’ll assume you have a proper tire gauge.

[toddwalton]

Originally Posted by jg4c

Door Jamb, tried and true. Obviously, cold only.
I’ll assume you have a proper tire gauge.

Here we go, pray for me.

[jg4c]

Originally Posted by toddwalton

Here we go, pray for me.

That looks to be an inflator with a built in digital gauge.
Do I see that correctly?

I have a different brand of inflator and have found
that it’s readout is consistently off by at least 1-2 PSI,
than the hand held gauge I use to check tire pressure.

I’ll overfill using the inflator, and then use the gauge
to adjust down to my preferred pressure.

YMMV…..🙏

[toddwalton]

Originally Posted by jg4c

That looks to be an inflator with a built in digital gauge.
Do I see that correctly?

I have a different brand of inflator and have found
that it’s readout is consistently off by at least 1-2 PSI,
than the hand held gauge I use to check tire pressure.

I’ll overfill using the inflator, and then use the gauge
to adjust down to my preferred pressure.

YMMV…..🙏

I've had luck with this one, I always fill it to 0.5 pounds over the recommended number and that compensates for inaccuracy or perhaps the bleed as I'm pulling off the valve. It sits charging in the garage for months at a time and has enough power to fill the tires with room to spare. Great for pool toys and bicycle tires too. Best $69 I've spent on a car accessory the last decade.

[wangyex]

I think when i got the car on p7 all seasons run-flat dealer pumped it at 36 front and 40 rear. When I got my x-ice snow winter tire with exact same setup, the tire shop went 36psi at all four corners