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[DUR]

Hi all:

I have 18" rims on my 135i, and I just wanted to know what tyre pressure you would recommend. I, unfortunately have Bridgestone runflats, just to let you know...

Thanks!!!

Cheers.

[mistermojorizin]

36 all around is recommended, some people run a little higher and get better gas mileage. search around here, ther's a thread about it

[DUR]

36??

Sorry, I'm from Europe, si I use "bar" pressure...

BMW says I should use 2.6 in front and 2.4 in the rear. I have 2.5 all around... (in my previous M3, with 19" I had 2.6 all around).

Cheers.

[creepy coupe]

Originally Posted by DUR

36??

Sorry, I'm from Europe, si I use "bar" pressure...

BMW says I should use 2.6 in front and 2.4 in the rear. I have 2.5 all around... (in my previous M3, with 19" I had 2.6 all around).

Cheers.

Are you sure, because my cars door card has the front's lower than the rears

I run 2.4 front 2.6 rear on 18's

[IDBMW]

I have the 135i with sport package and is says 36 psi in front and rear. My Z4 had staggered tires and they had different pressure in front and rear. Perhaps it has something to do with the NTSB and the TPMS. I bet the NTSB changed the regulations for door jam tire pressure stickers. You have to protect the lowest common denominator so we all suffer.

[Cris]

I'd say just put 35 psi or 2.4 bar all the way around.

This brings up a thought: if there's a place I can fill my tires with nitrogen, I would. Anyone thought about this?

[jeremyc74]

Originally Posted by Cris

I'd say just put 35 psi or 2.4 bar all the way around.

This brings up a thought: if there's a place I can fill my tires with nitrogen, I would. Anyone thought about this?

Nitrogen in tires is a complete and utter waste of money. Air is 79% nitrogen anyway. Your tires will wear out LONG before the oxidation gets to them, and the very minor difference in pressure between hot and cold isn't something you're going to be able to feel on a steet car, especially one with run-flats on it.

Just stick to regular compressed air.

[DUR]

Thank you all for your help!!!

I understand I should try with 2.4 or 2. all around then, is that so??

I'm probably going to change the RFT's to normal tires soon... should I keep the same pressure??

Cheers.

[Stratos]

I would reccomend adding about 15% over reccomended stock pressure.

With higher pressure the wheel can withstand much more than with low pressure. i.e. if you hit a pothole real bad you might bend the rim, but with 20% extra you might be okay.

It is much worse for both handling, security and fuel economy to have too low pressure than to have too high pressure.

Here is an article about the subject.
Pretty good article, but it is in norwegian, so i put it trough google translate. Bear over with the automatic translation:
http://translate.google.com/translat...-8&sl=no&tl=en

[Stratos]

Conversion table:

[Cooldaddygroove]

Originally Posted by Stratos

With higher pressure the wheel can withstand much more than with low pressure. i.e. if you hit a pothole real bad you might bend the rim, but with 20% extra you might be

Actually, the harder you make the tire by adding more air, the more an impact to a sharp object will transfer to the rim, increasing the chance of bending your rim.

[Stratos]

Originally Posted by Cooldaddygroove

Actually, the harder you make the tire by adding more air, the more an impact to a sharp object will transfer to the rim, increasing the chance of bending your rim.

Partly correct, but you also distribute the energy more even onto the rim, and rims usually copes better with that.

Worst case is if you hit a edge/hole and the tire gets copressed so the impact is directly on the rim. That may happen if the pressure is too low.

This of course applies to low profile wheels. High profile rubber does not have the same issues.

[Kris]

Does having non stock tyres (225/40/18 and 255/35/18) make a diff to the pressures required? my car is riding a bit firm and im using like 40PSI

[pit1]

Don't mean to whore the thread....Just a to keep ontop of your tire pressure. I'm usually REALLY anal about it, checking once every other week. I let it slide a few weeks and hopped in the car yesterday morning, a bit chilly, to TPM alarm and 25PSI ALL AROUND!!!!!!!!!! WOOPS!!!!!

no wonder my avg mpg dropped to 19. As the weathers cools off, check them and check them again...oh and tell your friends and family to check them.

[Stratos]

Thats why i always got this with me.

[JME]

Originally Posted by jeremyc74

Nitrogen in tires is a complete and utter waste of money. Air is 79% nitrogen anyway. Your tires will wear out LONG before the oxidation gets to them, and the very minor difference in pressure between hot and cold isn't something you're going to be able to feel on a steet car, especially one with run-flats on it.

Just stick to regular compressed air.

I used to think that too, but apparently it isn't the oxygen, but rather the water vapor that causes so many issues. However, for normal street driving i agree, nitrogen isn't the best value unless you can get it cheap.

[gio]

Originally Posted by JME

I used to think that too, but apparently it isn't the oxygen, but rather the water vapor that causes so many issues. However, for normal street driving i agree, nitrogen isn't the best value unless you can get it cheap.

Go with helium. It is lighter than air so it will make your wheels lighter improving performance and fuel economy.

:biggrin: