Run Flat Tire Pressure

Picklito · 04-28-2007, 11:00 PM

New here. Great site. Did a search but couldn't find exactly what I'm looking for...

Just swapped my '99 528i sport for an '07 328i sport/premium/cold. Fantastic car, but didn't have 'quite' the same steady-as-a-rock, anchored down feeling as the 528 (which was an amazing freeway cruiser). So I started checking around and found that the run flats were delivered with 41 psi at all corners. Set them to the door jamb numbers and that was better, but still it's pretty harsh and darty. So I've been experimenting downward. Went to 32 all around... better still. Today I went to 28 all around and it really seemed to click. Much more steady and solid feeling. Also, I finally got what looks like even contact out to nearly the edges of the tread, which is often a helpful indicator.

The run flats seem a bit stiff and harsh. I'm not at all worried about running 28 psi with 17's, but I'm just curious what the rest of you are running to get the run flats to feel 'right?'

Thanks in advance. Again, awesome site.

Chesmu · 04-28-2007, 11:04 PM

I like the harsher feel, so i have 36 in front and forty in back on the e90 (door jamb numbers). Other posters have mentioned that releasing some pressure definitely makes the ride softer.

ROCKETRON · 04-29-2007, 12:14 PM

I have a 320d m-sport on staggered 17 inch wheels and run 32/33 which is close to 2.1/2.2 in door jam.

FotiosF90M5 · 04-29-2007, 12:21 PM

I think 28 is a little too low.Its probably more comfortable but its not good for tire wear or fuel economy.You can also dent the wheel easier.IMHO

Picklito · 04-29-2007, 06:33 PM

Thanks for the comments.

What I should have included is that I drive like an old man. This is not a race car and sees no track time and nothing more aggressive than a really fun freeway ramp.

Yes, I agree, pressures that are TOO low will drop mileage and increase tire wear, but this is one stiff tire. Doubtful that 28 is too low for this particular tire which is the reason for this thread (if I put 28 psi into the Michelins on my wife's 17"/45-series FWD car that would be too low. They'd bulge like crazy, handling would be horrible, and I'm SURE the wear would be rapid. Rim damage would also be a concern. Those seem happy at about 36 psi front and 32 psi rear and the ride is good... but they're not run flats). Rim damage would be a big surprise on the 328 with 45-series tires and that stiff run flat sidewall. Aren't they supposed to at least be 'driveable' when pressure is ZERO??

I'm also wondering about the bad wear that many are experiencing on the outer tread block. Mine were barely even showing signs of road contact at the higher pressure. Perhaps they're only making contact on harder corners. Or pehaps they're getting dragged along a bit by the slightly larger diameter in the very center of the tread... and feathering. Now, at the lower pressure, they appear to be making good contact all the way across. I've only got 600 miles on the car, and about 150 miles at 28 psi.

Whaddaya guys think? I have to say I'm pretty happy at 28 psi. Am I the only one?

04-28-2007, 11:00 PM	#1
Picklito Enlisted Member 0 Rep 33 Posts Drives: 2007 328i Sparkling Graphite Join Date: Apr 2007 Location: the other left coast iTrader: (0)	Run Flat Tire Pressure New here. Great site. Did a search but couldn't find exactly what I'm looking for... Just swapped my '99 528i sport for an '07 328i sport/premium/cold. Fantastic car, but didn't have 'quite' the same steady-as-a-rock, anchored down feeling as the 528 (which was an amazing freeway cruiser). So I started checking around and found that the run flats were delivered with 41 psi at all corners. Set them to the door jamb numbers and that was better, but still it's pretty harsh and darty. So I've been experimenting downward. Went to 32 all around... better still. Today I went to 28 all around and it really seemed to click. Much more steady and solid feeling. Also, I finally got what looks like even contact out to nearly the edges of the tread, which is often a helpful indicator. The run flats seem a bit stiff and harsh. I'm not at all worried about running 28 psi with 17's, but I'm just curious what the rest of you are running to get the run flats to feel 'right?' Thanks in advance. Again, awesome site.
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04-28-2007, 11:04 PM	#2
Chesmu Brigadier General 89 Rep 3,011 Posts Drives: 2013 X6 Join Date: Dec 2005 Location: Phoenix,AZ iTrader: (2) Garage List 2006 330i [0.00] 2006 330i [0.00]	I like the harsher feel, so i have 36 in front and forty in back on the e90 (door jamb numbers). Other posters have mentioned that releasing some pressure definitely makes the ride softer. __________________ "Teach the ignorant. Ignore the stupid."
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04-29-2007, 12:14 PM	#3
ROCKETRON 320D M-sport le-mans blue 12 Rep 152 Posts Drives: E90 320D M-Sport le-mans blue Join Date: Aug 2006 Location: N.W London UK iTrader: (0)	I have a 320d m-sport on staggered 17 inch wheels and run 32/33 which is close to 2.1/2.2 in door jam. __________________ ROCKETRON MAZDA CX5 2.2D 175 AUTO AWD SPORT NAV. E90 320D M-Sport Lemans blue/beige leather/wood/auto/lumbar support/folding mirrors/through load/bluetooth/pro satnav,i-drive/voice control. NOW SOLD
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04-29-2007, 12:21 PM	#4
FotiosF90M5 ///M Specialist South Shore BMW 772 Rep 7,108 Posts Drives: 2021 M5 Comp BHG/Silverstone Join Date: Jan 2007 Location: South Shore, MA iTrader: (62)	I think 28 is a little too low.Its probably more comfortable but its not good for tire wear or fuel economy.You can also dent the wheel easier.IMHO __________________ 2021 M5 COMPETITION LCI Brands Hatch Gray on SIlverstone, carbon roof, comp wheels, Mperf splitter, carbon pro spoiler, carbon diffuser , carbon paddles, executive pkg. Dinan HAS, RaceChip, dinan spacers, FC stud kit, etc
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04-29-2007, 06:33 PM	#5
Picklito Enlisted Member 0 Rep 33 Posts Drives: 2007 328i Sparkling Graphite Join Date: Apr 2007 Location: the other left coast iTrader: (0)	Thanks for the comments. What I should have included is that I drive like an old man. This is not a race car and sees no track time and nothing more aggressive than a really fun freeway ramp. Yes, I agree, pressures that are TOO low will drop mileage and increase tire wear, but this is one stiff tire. Doubtful that 28 is too low for this particular tire which is the reason for this thread (if I put 28 psi into the Michelins on my wife's 17"/45-series FWD car that would be too low. They'd bulge like crazy, handling would be horrible, and I'm SURE the wear would be rapid. Rim damage would also be a concern. Those seem happy at about 36 psi front and 32 psi rear and the ride is good... but they're not run flats). Rim damage would be a big surprise on the 328 with 45-series tires and that stiff run flat sidewall. Aren't they supposed to at least be 'driveable' when pressure is ZERO?? I'm also wondering about the bad wear that many are experiencing on the outer tread block. Mine were barely even showing signs of road contact at the higher pressure. Perhaps they're only making contact on harder corners. Or pehaps they're getting dragged along a bit by the slightly larger diameter in the very center of the tread... and feathering. Now, at the lower pressure, they appear to be making good contact all the way across. I've only got 600 miles on the car, and about 150 miles at 28 psi. Whaddaya guys think? I have to say I'm pretty happy at 28 psi. Am I the only one?
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