Bbyboomer

While I am generally a fan of a TPMS I rely on the old fashion tire quage. I will admit I'm OCD when it comes to prior tire pressures.I have issues with the dash read out on my 2013 ES350 to the point I had it back several times to look at it. My tire pressures were "according" to my dashboard all over the place, some too low,some way too high. They assured me (or tired) that the system was working as it was suppose to. Once again I had the car back,this time to "remove" the gas from the tires and inflate them with regular air. It's been near two months since I have the gas removed.My pressures are fairly close to normal when cold but go wild when hot. Is this possible? One very important point to make. i live in LAS VEGAS,desert heat for now is up to 115 some days. The road surfaces are even hotter. I understand all that, but why the vast difference in tire pressures? Does anyone else have little faith in their TPMS as I do ?

Dave Mac

I too am pretty OCD about tire pressure and have been impressed with the accuracy consistency of the TPMS in my 2013 ES 350. In fact the tire pressure is what I usually have displayed while driving - sometimes mileage since last fill. Whenever I compare the tire pressure to one or more of my three tire guages it is always right on. Sorry to hear yours is not working as well as mine.

And I have only air in my tires.

Dave Mac

lesz

The TPMS on my ES consistently reads the tire pressures at about 1-2 pounds lower than any of the 3 tire pressure gauges that I have, and those three gauges are all consistent with each other. When driving and after the tires have warmed up, the pressures shown by the TPMS generally rise by about 3-4 pounds over the cold tire pressures, but they do not fluctuate like those of the OP. Once the tires are warmed up, pressure might vary by a pound or so from one minute to the next, but not by more than that.

SLH

Tire pressure really does vary by several PSI, between a low on a cool morning, and a high after driving at highway speed for some miles. A ten percent difference is not unusual. They really do warm up during maneuvering, while driving at speed, and even while parked in the sun.

Here is an article that explains some of the tech: http://www.tirerack.com/tires/tirete....jsp?techid=73

AFRetired

I'm still working on the "remove the gas (nitrogen) and replace it with regular air." Since regular air is 78% nitrogen already, exactly what huge practical difference is there really?

Need4Speed

the whole thing of fill with nitrogen and not air is IDK i wont say anything.

But we fill all our tires and our clients tires with gold old O2.

lesz

I think that it may well be that the biggest difference between regular air and nitrogen tire fills is the fact that dealers are charging $100 or more for the nitrogen fills.

It also seems to me that, even if there was some real benefit to nitrogen fills, that benefit has to be relatively short-lived. Where I live, for example, the range of temperatures from the highest to the lowest in the last 12 months has been over 120 degrees. Every couple of weeks, I check the pressure in the tires on my vehicles and either let air out or add air to compensate for changes in the temperature. If I were inclined to put nitrogen in my tires, it seems that, with regularly letting air out to compensate for warmer temperatures or adding air to compensate for lower temperatures, it wouldn't take long before much of the nitrogen was gone and was replaced by regular air, and, unless I was prepared to regularly pay for having new nitrogen added, I'd end up with mostly regular air before too long.

AFRetired

Pure Oxygen? Really?

SDRider

I've never filled my tires with anything but regular old air... not even my motorcycle tires.

Arty101

I heard nitrogen is more inert and doesn't change with temp much as regular air. I also heard it may make a difference on the race track, it's more hype and a sales opportunity to the consumers.

SLH

It really is silly to pay for nitrogen for street car tires.... It makes sense for airplanes, but not for the reason that most people expect.

The thing about "dry nitrogen" is, that it is "dry". As in, no water. Regular air has some water vapor. The process of concentrating the nitrogen into a pressure tank eliminates the other gases, but it also eliminates the water vapor. Filling a tire with damp air also puts a little bit of water into the tire with each fill. Filling a tire with dry nitrogen does not add any water vapor.

In airplanes, the tires get very cold during high-altitude flight. Any water that is in the tire can freeze in a puddle at the bottom of the (non-spinning) tire. Then, when the airplane lands, the tires spin up to 150 mph almost instantly. If there is frozen water in one spot, it throws the tire off-balance, and can cause a flat tire. They use dry nitrogen to fill airplane tires to prevent the accumulation of water in the tire, to prevent the ice, to prevent the flat tire during landing.

Cars don't have that problem. Cars don't fly at high altitude, and they don't land on a runway at 150 mph. If there is some ice in the tire on a cold morning, it is on the flat spot at the bottom of the tire (where the tire is compressed against the road by the weight of the car). Any little bit of ice in the tire breaks up during the first bit of low-speed driving, and melts as the tire warms up. Driving on a cold tire is not dangerous at low speeds typical of neighborhoods and surface streets. The ice is long gone before you reach the highway or the race track.

If the nitrogen is free, and you feel like it, it doesn't do any harm to put some in your tires. But, I don't think it is worth paying extra.

lesz

If you read evaluations from sources like Consumer Reports, Edmunds, etc., they all seem to agree that there can be some benefit to filling tires on passenger cars with nitrogen, but they also seem to agree that the benefits are quite insignificant.

For example, with nitrogen, pressure changes that come with temperature changes are smaller than with regular air in the tires, but those pressure changes aren't much smaller. Further, for the nitrogen to have any benefit at all, it must be virtually pure nitrogen. The numbers that I've seen have been that there must be at least 93% or 94% pure nitrogen, and as soon as any regular air at all is added to the tire, any minimal benefits from the nitrogen disappear. From about the beginning of October to January, as temperatures are transitioning into the dead of winter, I'll typically add air, a couple of pounds at a time, to my tires about 4 or 5 times every two or three weeks. I'm certainly not going to be inclined to have to go the dealer or to a tire store 4 or 5 times every fall and early winter to add nitrogen to the tires. Typically, the charge for doing so is $4-5 per tire, but, even if the nitrogen top-offs are free, I don't want to spend the time to have to drive to the dealer or tire store and, then, wait while they top off the tires.

bc6152

A great explanation SLH. One that almost anyone can understand.

ALIGN

To get accurate tire pressure get a decent digital pressure gauge. The car displays the pressure in whole numbers while digital pressure gauge displays with 2 decimal. Try to match it as close a possible up to the decimal.

With nitrogen, my highest tire pressure reading is 35 to 36# on a hot day of 2-3 hours of driving. on a 80 deg weather I get 34 on the front, 33 on the back. In the morning they stabilized at 31# on all tires.

LexBob2

I'd never pay for nitrogen in my tires, but my last ES350 came with it from the dealer and if they added air during service it was nitrogen. I doubt that there was any mpg improvements with it, but I can say that for the three years I owned the car, I rarely, if ever, had to adjust the air pressures even after severe hot or cold conditions. So it did seem to help maintain the desired tire pressure. Coincidence? I don't know but since it came in the tires and didn't cost extra no complaints here.