Nitrogen in tires?

[FSETH]

Originally Posted by Low Note

I was told by the Mercedes dealer (who may or may not be correct) that you should not top off a nitrogen filled tire with regular air. That, according to him, will introduce some water into the mix, thus negating the effectiveness of the "dry" nitrogen.

That is what I figured. With only a few months of life left on my tires, I am not too worried about that.

[FSETH]

Originally Posted by rayxi

I don't buy it. Who's going to run around looking for a N2 top up when their tire is low?

That is the thing. You only have to do it once or twice over the typical life of the tires. You probably end up saving time over the long run of having to find an air compressor every few months.

[Low Note]

Originally Posted by rayxi

I don't buy it. Who's going to run around looking for a N2 top up when their tire is low? The important thing is to not drive around with underinflated tires, not whether or not you may have 10% regular air vs pure N2.

Introducing water is another thing. Even if you have regular air in your tires you should avoid poor quality air (moist). I've seen gas stations that had water dripping out of the air hose.

This is indeed a common problem. Probably best thing to do is either get a good 12v air compressor (I've never seen one that actually worked) or a tank of compressed air to use when adding air to the tires. I always used regular air until i got my last, now retired Mercedes with free nitrogen fill from the dealer. Never had to adjust air pressure in any of the tires in two years I owned the car, even when I drove up to very cold northern Michigan. But since I've never had rft's before (will find out in two weeks when I get my new X6), people (thank you Midwest for your help) with much more experience with rft's than I have suggested that the nitrogen is totally unnecessary for street use.

[Skywagon]

I apologize if this post is redundant. Save your money. Nitrogen is used in aircraft tires for two reasons. Extremely high pressures, I've seen some on airliners as high as 120 psi. Also because of the incredible temperature variations the tires are subjected to. Let's say it's 100F on the surface coupled with a 10,000 foot take off roll on a heavy airplane and then a -60F at 39,000 feet for hours at cruise. I guess nitogen does not expand and contract as much as good old air. No, I never used a laptop computer in the cockpit. I did sleep and read the paper though. It's a long way from NY City to Tokyo. Most importantly, when it comes to pilots, the old cliche' "you get what you pay for" is truly profound!!

[motordavid]

OT...

Originally Posted by Skywagon

...No, I never used a laptop computer in the cockpit. I did sleep and read the paper though. It's a long way from NY City to Tokyo. ...

I rode on those flights 2 dozen plus times...maybe you were driving up
front?!

[motordavid]

Originally Posted by Low Note

This is indeed a common problem. Probably best thing to do is either get a good 12v air compressor (I've never seen one that actually worked) ...

I have been using a 20+ yr old Black & Decker portable, to pump up the
rides in the Stable; never a problem with fill or moisture.

This is the newer version, I have at the FLA Joint. My orig., still being used, is the older version.
GL,mD

[Low Note]

Originally Posted by Skywagon

I apologize if this post is redundant. Save your money. Nitrogen is used in aircraft tires for two reasons. Extremely high pressures, I've seen some on airliners as high as 120 psi. Also because of the incredible temperature variations the tires are subjected to. Let's say it's 100F on the surface coupled with a 10,000 foot take off roll on a heavy airplane and then a -60F at 39,000 feet for hours at cruise. I guess nitogen does not expand and contract as much as good old air. No, I never used a laptop computer in the cockpit. I did sleep and read the paper though. It's a long way from NY City to Tokyo. Most importantly, when it comes to pilots, the old cliche' "you get what you pay for" is truly profound!!

What the heck. For forty bucks with tire-life free refills, I went ahead and had my dealer do the nitrogen on my new 2010 X6. 5.0. That's what it costs for three people to have lunch at the local generic Garbage Burger. We did 41/42 PSI front/rear and since I do a lot of driving between warm Virginia and very cold Michigan (!) every winter, I decided that it certainly couldn't hurt. After spending so much on this vehicle, and paying to have a 3M clear bra installed, why not splurge? I'll save those forty bucks just by not going to Starbucks for a week (good reason to get out of that habit since I hate their coffee anyway).

[JCL]

Originally Posted by Low Note

We did 41/42 PSI front/rear and since I do a lot of driving between warm Virginia and very cold Michigan (!) every winter, I decided that it certainly couldn't hurt.

Not sure about the X6, maybe it is different, but the X5 has a spec of 32 psi front and rear, even loaded, unless you are regularly travelling at autobahn speeds (and even then they don't recommend 41/42). All it can hurt is premature wear on your tires, and a harsher ride, but it's your call.

[Low Note]

Originally Posted by JCL

Not sure about the X6, maybe it is different, but the X5 has a spec of 32 psi front and rear, even loaded, unless you are regularly travelling at autobahn speeds (and even then they don't recommend 41/42). All it can hurt is premature wear on your tires, and a harsher ride, but it's your call.

The owners manual for the 2010 X5/X6 recommends 33/33 for the X6 19" all season tires, but states that "for sporting driving and speeds over 100 mph" that 41 front/42 rear is recommended. My mechanic who races BMW's also suggested this setting. The ride is not too harsh, and the vehicle handles extremely well. He also mentioned that 33/33 will probably cause cupping with rft's.

[JCL]

I only have access to a 2009 owner's manual for the X6 5.0, so perhaps they have changed the recommendation. In that manual, over 100 mph sustained speeds, with four passengers, the recommendation for 19" tires is still 33/33. You have to go to the maximum gross vehicle weight (4 passengers plus a full load of luggage), and sustained speeds over 100 mph, to get up to 36/39 psi front/rear. You need all of those conditions, plus the 21" tire option, to get to 42 psi for a BMW recommendation. No worries, run them where you like, but I have never seen 33 psi cause cupping with any of my BMW vehicles, including those with RFTs. I have seen 39 psi and over cause accelerated wear in the centre of the tread.