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      11-20-2011, 03:49 PM   #1
mav5125
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Tyre pressures

Hi all. Just wondering if running 42psi on 19\" run flats is ok or a bit too high.

Recall the manual (which I don\'t have anymore) said 35 front and 42 rear. Just want to check.

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      11-20-2011, 04:49 PM   #2
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i've just check my manual 36 front 42 rear for the 19 inches
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      11-20-2011, 09:06 PM   #3
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I was looking at the manual today and it says 36 front and 42 rear driving up to 100mph and 44 rear over 100mph. But I suspect with hotter climate you should reduce it. I assume the manual refers to RFT. Best to make a call to your SA.
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      11-20-2011, 09:08 PM   #4
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Quote:
Originally Posted by mav5125 View Post
Hi all. Just wondering if running 42psi on 19\" run flats is ok or a bit too high.

Recall the manual (which I don\'t have anymore) said 35 front and 42 rear. Just want to check.

Thanks
Mav
how hot does it get where you live?
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      11-22-2011, 01:30 AM   #5
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How about Non RFT?? which I use Nitrogen and fill 38 F, 42 R
any recommendation??
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      11-23-2011, 03:01 AM   #6
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Originally Posted by Memphis1 View Post
how hot does it get where you live?
well its coming up to summer now and though it's only about 25c (77F) it should get up to about 40c (104F) during the hottest times.
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      11-23-2011, 07:56 AM   #7
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Quote:
Originally Posted by Z4@Phuket View Post
How about Non RFT?? which I use Nitrogen and fill 38 F, 42 R
any recommendation??
When I drove my Z4 with the RFT I constantly lost pressure and had to adjust the pressure every week almost.

How often do you check your tire pressure? I guess with Non-RFT it holds the pressure a lot better?
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      11-23-2011, 08:15 AM   #8
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Quote:
Originally Posted by Z4@Phuket View Post
How about Non RFT?? which I use Nitrogen and fill 38 F, 42 R
any recommendation??
Normal air is already 78.08% Nitrogen, While it does not absorb water like air, I don't think the difference in a Lilly loaded vehicle (like a car) would make a noticeable difference. Some folks swear by Nitrogen but as of yet there have been any diff inactive studies involving passenger cars.
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      11-24-2011, 08:23 AM   #9
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Source Popular Machanics


Q: Is there any advantage to using nitrogen instead of compressed air in tires? Will I notice improved fuel economy or a smoother ride? Will my tires last longer?

A: Sort of. From the top: Air is 78 percent nitrogen, just under 21 percent oxygen, and the rest is water vapor, CO2 and small concentrations of noble gases such as neon and argon. We can ignore the other gases.

There are several compelling reasons to use pure nitrogen in tires.

First is that nitrogen is less likely to migrate through tire rubber than is oxygen, which means that your tire pressures will remain more stable over the long term. Racers figured out pretty quickly that tires filled with nitrogen rather than air also exhibit less pressure change with temperature swings. That means more consistent inflation pressures during a race as the tires heat up. And when you're tweaking a race car's handling with half-psi changes, that's important.

Passenger cars can also benefit from the more stable pressures. But there's more: Humidity (water) is a Bad Thing to have inside a tire. Water, present as a vapor or even as a liquid in a tire, causes more of a pressure change with temperature swings than dry air does. It also promotes corrosion of the steel or aluminum rim.

If I ever need to top off a tire when I'm out on the road, I'll always briefly depress the tire chuck's valve with my thumbnail and vent some air. If my thumb gets wet, there's water in the line. Some gas stations don't do a very good job of keeping the humidity out of their air system. I don't even like to use a water-based tire-mounting lubricant unless I can let the tire bake in the sun for a couple of hours before I air it up and seat the bead. I've dismounted tires (not mine) that had several quarts of water inside—probably from a compressed-air hose that collected water and was never purged properly.

How is water relevant to a nitrogen discussion? Any system that delivers pure nitrogen is also going to deliver dry nitrogen. Filling tires with nitrogen involves filling and purging several times in succession, serially diluting the concentration of oxygen in the tire. This will also remove any water.

It's certainly simple, although time-consuming, for a tire technician to fill and bleed tires. But most shops use a machine that not only generates almost pure nitrogen by straining the oxygen out of shop-compressed air, but will also automatically go through several purge cycles unattended. Some shops have been charging as much as $30 per tire for this service. I think that's too much. If you're buying a new tire, it should be far less. Still, the nitrogen generator, filling system and technician's time aren't free—the dealer is entitled to some return for that.

So, to answer your specific questions: With nitrogen, your tire pressures will remain more constant, saving you a small amount in fuel and tire-maintenance costs. There will be less moisture inside your tires, meaning less corrosion on your wheels. You will not be able to feel any difference in the ride or handling or braking, unless your tire pressures were seriously out of spec and changing to nitrogen brought them back to the proper numbers

Read more: Nitrogen vs Air In Tires - Why Nitrogen in Tires - Popular Mechanics
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      01-11-2012, 11:15 PM   #10
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Didn't want to start a new thread: during colder weather, I noticed that the PSI actually went up, so apparently no need to pump the tires as often vs warmer weather - is this the usual case?
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      01-12-2012, 12:05 AM   #11
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Quote:
Originally Posted by tranquility View Post
Didn't want to start a new thread: during colder weather, I noticed that the PSI actually went up, so apparently no need to pump the tires as often vs warmer weather - is this the usual case?
I would suspect that during colder weather the pressure drops, which causes more flex in the tire, creating more heat and raising the pressure.
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      01-12-2012, 12:12 AM   #12
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Quote:
Originally Posted by Z4@Phuket View Post
Source Popular Machanics


Q: Is there any advantage to using nitrogen instead of compressed air in tires? Will I notice improved fuel economy or a smoother ride? Will my tires last longer?

A: Sort of. From the top: Air is 78 percent nitrogen, just under 21 percent oxygen, and the rest is water vapor, CO2 and small concentrations of noble gases such as neon and argon. We can ignore the other gases.

There are several compelling reasons to use pure nitrogen in tires.

First is that nitrogen is less likely to migrate through tire rubber than is oxygen, which means that your tire pressures will remain more stable over the long term. Racers figured out pretty quickly that tires filled with nitrogen rather than air also exhibit less pressure change with temperature swings. That means more consistent inflation pressures during a race as the tires heat up. And when you're tweaking a race car's handling with half-psi changes, that's important.

Passenger cars can also benefit from the more stable pressures. But there's more: Humidity (water) is a Bad Thing to have inside a tire. Water, present as a vapor or even as a liquid in a tire, causes more of a pressure change with temperature swings than dry air does. It also promotes corrosion of the steel or aluminum rim.

If I ever need to top off a tire when I'm out on the road, I'll always briefly depress the tire chuck's valve with my thumbnail and vent some air. If my thumb gets wet, there's water in the line. Some gas stations don't do a very good job of keeping the humidity out of their air system. I don't even like to use a water-based tire-mounting lubricant unless I can let the tire bake in the sun for a couple of hours before I air it up and seat the bead. I've dismounted tires (not mine) that had several quarts of water inside—probably from a compressed-air hose that collected water and was never purged properly.

How is water relevant to a nitrogen discussion? Any system that delivers pure nitrogen is also going to deliver dry nitrogen. Filling tires with nitrogen involves filling and purging several times in succession, serially diluting the concentration of oxygen in the tire. This will also remove any water.

It's certainly simple, although time-consuming, for a tire technician to fill and bleed tires. But most shops use a machine that not only generates almost pure nitrogen by straining the oxygen out of shop-compressed air, but will also automatically go through several purge cycles unattended. Some shops have been charging as much as $30 per tire for this service. I think that's too much. If you're buying a new tire, it should be far less. Still, the nitrogen generator, filling system and technician's time aren't free—the dealer is entitled to some return for that.

So, to answer your specific questions: With nitrogen, your tire pressures will remain more constant, saving you a small amount in fuel and tire-maintenance costs. There will be less moisture inside your tires, meaning less corrosion on your wheels. You will not be able to feel any difference in the ride or handling or braking, unless your tire pressures were seriously out of spec and changing to nitrogen brought them back to the proper numbers

Read more: Nitrogen vs Air In Tires - Why Nitrogen in Tires - Popular Mechanics

On the other side, Tire Rack says
..."Is it worth it? If you go someplace that provides free nitrogen with new tires, why not? Additionally we’ve seen some service providers offering reasonable prices of about $5 per tire (including periodic adjustments for the life of the tire) to a less reasonable $10 per tire (with additional costs for subsequent pressure adjustments) or more as part of a service contract, which we believe exceeds the value of nitrogen’s benefit.

Rather than pay extra for nitrogen, most drivers would be better off buying an accurate tire pressure gauge and checking and adjusting their tire pressures regularly.?.". Over here at Euro18 per wheel I don't think it makes sense.
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