Correct Tire Pressure?

[txp135]

Hi, The manual says 41 psi, but the tires say max pressure is 40psi. It does ride kinda hard with 40 psi. What should the pressure be if car normally drives with 2 adults upfront and 2 todds in the back? Thanks.

[ILoveMPower]

I run 33 in the front 35 in the rear

[txp135]

Thanks, I'm also wondering why they would say 41 psi in the manual when most people don't run them that high?

[BMWCCA1]

BMW switched to listing only maximum-load pressure suggestions years ago. Probably something having to do with some brain-trust loading the car down with five passengers and full trunk at 26 psi and suing over the result. I believe Euro-spec cars still show pressures for different load situations. Anyone care to share from their Euro model?

I'd start around mid thirties all around and add more in the rear an necessary to increase understeer or more in front to increase oversteer (and vice-verse). That's the short version.

[Qsilver7]

I believe Euro-spec cars still show pressures for different load situations. Anyone care to share from their Euro model?
I don't have a Euro model...but the tire pressures given for areas outside the USA/Canada are given in my owners manual. :)

BTW, the recommeded tire pressure is what the car's MFG suggests (which is what's listed in the owners manual and the label on the driver's door jamb).

The tire pressure listed on the tire's sidewall is not a recommendation...but a WARNING by the tire MFG to NOT over-inflate the tire beyond what's listed. The MAX tire pressre is for safety reasons only based on the tire's construction & speed rating etc. The tire MFG can't really make a recommendation for tire pressure since they don't know what car (its weight, engine HP, torque, performance and handling, etc) the tire is going to be mounted on...they just make the tire to a specific safety and performance spec.

http://www.bimmerboard.com/members/q/original/E34%20Tire%20Pressure%20Chart.jpg

[RobPatt]

...unless we're saying that north american models weigh differnet so need different pressures....?

i'm probably wrong, but run 39 front 41 rear 'cause I "think" that's what it says in my door jamb for 235/45 17inch tires....

and i'm real happy with tirelife, handling, etc...at those pressures... BUT I think it's kinda noisy..don't know if that's related.

[pingu]

I don't know what the max load pressures are (the max pressure is for if you've got 4 adults and a whole bootfull of luggage) but I think the normal pressures are:

Front: 33psi
Rear: 36psi

They both increase if fully loaded but the rears increase (not suprisingly) by the most.

[e34m30SF]

hmm...my 1990 US-spec manual says 29/35 f/r for up to 4 people and 35/44 f/r for max load.

Personally, I think 29 is a bit low for the front, since it looks really squat, so i like to go 32. But then i read somewhere that you need to maintain the differences in pressure f/r because it may affect the handling and dynamics of the vehicle in cornering...


Sounds like bs, but then again, i like to play it safe. I knew someone who had a '00 323ci and it gave a whole slew of numbers. He just got fed up and put 32 all around. Worked fine for him...

[ThoreauHD]

I do 38 in front and 39 in the rear. It's just a preference of feel really. I like even and stable. If you are cornering on a track you don't do lower unless you like riding on your rims, and off into the sunset.

[g7syw]

I run mine at 35 all round - handles fine, its only normally got me inside and no luggage....

The (UK) manual suggests 33 at the front and 35 rear.

[Ross]

BMW switched to listing only maximum-load pressure suggestions years ago. Probably something having to do with some brain-trust loading the car down with five passengers and full trunk at 26 psi and suing over the result. I believe Euro-spec cars still show pressures for different load situations. Anyone care to share from their Euro model?

I'd start around mid thirties all around and add more in the rear an necessary to increase understeer or more in front to increase oversteer (and vice-verse). That's the short version.
I think your inflation advise is backwards.

[Torque]

I know the 535i on 225/60/15 calls for 29 front and 35 rear ... maybe a few more psi for the 540 due to more weight, but I honestly doubt it's 41psi.

[cary]

Just to note, the manual calls for pressures in the high 30's range (something like 38psi front and 41psi rear) for the M5 with 17's as the standard fitments.

[Ross]

Outside of the USA and Canada they aren't likely to have their pants sued off because some moron had underinflated tires and crashed. Also less likely to have four 300 pounders jammed in.
Reading between the lines 29 front and 33 rear seems to be what is considered correct with up to four people.