45 PSI tire pressure and 70 MPH = 24.3 MPG

[dcdude]

The tech who did the PDI (Pre-Delivery Inspection) Did NOT air down the tires properly.

Makes sense, but why did they ship at such a 'high' pressure?

 

[JB.]

the 2013 comes with P tires?

As 1engineer mentioned........ also the entire 4th gen and probably the entire 3rd gen (from factory).

 

[eddiebx]

Makes sense, but why did they ship at such a 'high' pressure?

Easier to let some air out than put it back in? lol

 

[STLDAVE]

Makes sense, but why did they ship at such a 'high' pressure?

The tires are filled from the factory with pure nitrogen. Since the destination temperature and altitude will vary that pressure the factory overfills them. Overfilling the tire allows the pressure to be adjusted to the correct level at the destination without having to add air. Adding air introduces moisture, oxygen, etc. into the tire (unless pure nitrogen is used to increase the pressure). Do a search on why nitrogen is used if you have questions about that.

 

[Lolrax]

It must have felt like you were driving on a cloud, one time I was filled to 44 on my Limited and it felt really scary to me. I had no control.

 

[nevada]

As 1engineer mentioned........ also the entire 4th gen and probably the entire 3rd gen (from factory).

hm, interesting.

 

[dcdude]

It must have felt like you were driving on a cloud, one time I was filled to 44 on my Limited and it felt really scary to me. I had no control.

All the reviews I read said that the T4R ride was stiff and "bouncy" (relative to Highlander and CUVs). The truck handled great and didn't feel the ride was even that bad, but perhaps there's room for improvement?

Is the spec for the 20" LTD wheels higher than 32 PSI?

 

[1engineer]

The tires are filled from the factory with pure nitrogen. Since the destination temperature and altitude will vary that pressure the factory overfills them. Overfilling the tire allows the pressure to be adjusted to the correct level at the destination without having to add air. Adding air introduces moisture, oxygen, etc. into the tire (unless pure nitrogen is used to increase the pressure). Do a search on why nitrogen is used if you have questions about that.

Tires are filled that high for tying down during shipping from Japan by boat.

 

[Barry694]

Tire Pressure

As stated above. I have owned 24 or 25 Toyota/Lexus products. Most of them were built in Japan. However, I always dropped the pressure to near the door jamb recommendations. My previous 4Runner had 78,000 miles on Michelin LTX tires and they still looked good when I sold it. My present 5th Gen gets terrific mileage when on the open highway if I am not fighting a strong head wind (Have LTX MS2 tires). 24 is about normal. I have gotten 26. All purpose driving (I do not live in a large city) averages just a little over 19. I drive approximately 10 miles over the posted limited. However, I do not accelerate heavily from light to light. I also do not tow. My 2012 LS460AWD averages about 23 all purpose. But it is a V-8 and the car is a bit heavier. The 8 speed transmission helps a lot.

 

[jambo]

I just got my brand new 2013 and drove it from L.A. to San Diego this weekend. Before I left, I located the "correct" tire pressure on the driver's door jamb (32 PSI) and checked my tire pressure (just like our dads taught us!) I was surprised to see that each tire read about 45 PSI. I can only assume that was the "factory fill," so I didn't adjust anything.

Got in and drove the family of four plus weekend gear about 100 miles. Cruise control was set at 70 MPH. Our indicated MPG was 24.3 Needless to say, I'm very pleased with the new "gas guzzling SUV."

Any downside to running 45 PSI on-road? These are the stock 17" Dunlops or Bridgestones. My old Bronco specified 40 in the rears.

When you fill air at 45 psi with highway speeds the air insides heats up and pressure goes up. May cause blow out at 70mph to control our rigs is not going to be easy. Stick with manufacturers limits with nitrogen instead of air with the use off proper TPG you will be fine. Just remeber if you get 1 tire blow out the other 3 are on their way as well and hence very defective at this point. You get SUV pay for the fuel.we put so much money into mods and save pennies for fuel.

 

[dcdude]

They are shipped with 45 psi in the tires and the dealer is supposed to air them down.

The tech who did the PDI (Pre-Delivery Inspection) Did NOT air down the tires properly.

I don't see why the EPA wouldn't receive a T4R with 45 PSI tires to do its MPG testing. Maybe it's some conspiracy by TMC to game the EPA mileage figures and sell more trucks? Hmmmm...:evil:

 

[Viper45]

The tires are filled from the factory with pure nitrogen. Since the destination temperature and altitude will vary that pressure the factory overfills them. Overfilling the tire allows the pressure to be adjusted to the correct level at the destination without having to add air. Adding air introduces moisture, oxygen, etc. into the tire (unless pure nitrogen is used to increase the pressure). Do a search on why nitrogen is used if you have questions about that.

You might want to read this

One of the more important points, imo.

What about oxygen's affect on a tire? Doesn't nitrogen prevent tire aging?

There is a principle called the Law of Partial Pressure of Gases. Sometimes this is referred to as Dalton's Law after John Dalton (pictured), who discovered the principle. It states that a mxture of gases behaves like each gas is working independently - and you can separate the effects the various gases have by using their percentage in the mixture as the same as their percentage of the gas.

For example, nitrogen is 78% of the air, so at regular atmospheric conditions (14.7 psi), nitrogen acts like it is at a pressure of:

14.7 X 0.78 = 11.5 psi.

For tires, it means that pressurized air within a permeable membrane (the tire itself) will diffuse (lose pressure) through the tire according to the diffusion rate of each gas individually.

So if oxygen has a different diffusion rate that nitrogen (it does - oxygen diffuses more quickly!), then the amount of oxygen available to attack the rubber is also increased.

One might think that inflating a tire with 100% pure nitrogen would prevent oxygen from ever reaching the critical parts of the tire - the belt edges! Unfortunately, the Law of Partial Pressure of Gases also works in reverse. In spite of the nitrogen being under pressure, the oxygen in the atmosphere is under pressure compared to the oxygen inside the tire.

Put another way, if there is 100% nitrogen in a tire - and therefore no partial pressure of oxygen - then the partial pressure of oxygen outside the tires is 14.7 psi X 0.21 (21%) = 3.1 psi. That means that there is a pressure of 3.1 psi trying to push oxygen into the tire.

This effect was demonstrated by a paper delivered to Tire Society, Sept 25, 2007 by Don Amos - Study of Oxygen and Nitrogen Permeation through Tires with Monthly Top-off. Unfortunately, this paper was never published.

 

[jambo]

You might want to read this

One of the more important points, imo.

Some engineer are good on dreaming up useless theories. Put O2 in tires and you are basically driving bomb . Fire needs 3 things to start fuel in the tank, spark or a heat source from callipers ,and good old oxygen thanks to 4 tires. H2O in tires,ever tried to roll a drum full off it down hill.
Nitrogen is an inert gas so less chances of corrosion agreed you can not get 100 percent in tire unless its in a controlled chamber which does not happen. N2 does not change psi compared to air with friction or temperature changes. Hence all airlines use N2 in landing gear actuators and tires . From 40000 feet to sea level and from zero speeds to 160kph + in a flash and the tire holds up. Now for those off you wondering how I know this well 25 yrs plus aircraft maintenance in Uk kenya Usa and now canada. We used nitrogen in tires

 

[FrontRange4Runner]

I did vehicle durability testing for a while. Manufactures run many different tire types at different pressures over thousands of miles. I was fortunate enough to drive some amazing vehicles on many different tire types (snow, AT and performance...etc). Personally, if I'm running a stock tire, then it will be inflated to exactly what the manufacturer recommends. Why? They spend a ton of money figuring out which tire preforms best and at which psi the tire does so while yielding the best results overall (samples were taken 2x a day over 30+ vehicles - this includes psi and tread depth. The vehicles drove 20+ hours a day). Any tire is a compromise - period. Gains in one category loose in another. If you think you can simply inflate your tires and gain mpg without losing in another area then your fooling your self. Do you really think Toyota would accept the current millage of the Runner if all they had to do was inflate the tires and gain +2mpg or more? Poke around the net and you can find pictures of how a given tires "footprint" looks at speed (under inflated and over inflated). Under inflated or over inflated tires will loose a large amount of contact patch at speed while going through snow or water (or normal driving conditions) due to deformation. IMHO if you want better millage then buy an eco tire. If you want the best grip in the winter then buy a winter tire. If you want decent all around + off road, then buy an A\T. There is a ton of real science that goes behind each type, and if there were a tire that did everything, then we would all be fools not to have it.

 

[jambo]

I did vehicle durability testing for a while. Manufactures run many different tire types at different pressures over thousands of miles. I was fortunate enough to drive some amazing vehicles on many different tire types (snow, AT and performance...etc). Personally, if I'm running a stock tire, then it will be inflated to exactly what the manufacturer recommends. Why? They spend a ton of money figuring out which tire preforms best and at which psi the tire does so while yielding the best results overall (samples were taken 2x a day over 30+ vehicles - this includes psi and tread depth. The vehicles drove 20+ hours a day). Any tire is a compromise - period. Gains in one category loose in another. If you think you can simply inflate your tires and gain mpg without losing in another area then your fooling your self. Do you really think Toyota would accept the current millage of the Runner if all they had to do was inflate the tires and gain +2mpg or more? Poke around the net and you can find pictures of how a given tires "footprint" looks at speed (under inflated and over inflated). Under inflated or over inflated tires will loose a large amount of contact patch at speed while going through snow or water (or normal driving conditions) due to deformation. IMHO if you want better millage then buy an eco tire. If you want the best grip in the winter then buy a winter tire. If you want decent all around + off road, then buy an A\T. There is a ton of real science that goes behind each type, and if there were a tire that did everything, then we would all be fools not to have it.

Agreed word for word 100%

 

[1000MPH]

Which manufacturer? Car or Tire?
Of course it's a compromise.
I'm quite surprised that after all of that testing, you conclude that the door label is best for all types of driving and situations.

 

[FrontRange4Runner]

Which manufacturer? Car or Tire?
Of course it's a compromise.
I'm quite surprised that after all of that testing, you conclude that the door label is best for all types of driving and situations.

Cant say which manufacturers, but we ran cars and SUV's. They generally ran a couple different brands of tires for each vehicle type and would pick from there. I am not saying that the door sticker is the best for all situations, I am saying its the best -compromise- for all situations (this only applies to the OEM tires of course). I'm sure you could simply air up or down for different situations and achieve better results than whats on the door, but who is going to do that every day, for every separate situation encountered?

All I am really saying is that if your airing up to achieve better MPG then you will be loosing out in another area. It would suck to find out too late that your tires don't preform how you expected them to in the rain (or snow etc..). The manufacturers spend a ton of time and money figuring this stuff out so we don't have to lol that is until you stick some bigger M\T's on....

 

[1000MPH]

I've always believed that the mfgs recommend a lower pressure as a cheap way to achieve a softer road feel. The compromise would be a slight decrease in high speed handling and an increase in uneven tire wear. I suppose the added benefit would be certain driving conditions like mud or snow but that could be debatable as well.
I've also understood that the mfgs are "allowed" to goose the psi for their EPA testing.
...and probably ground clearance specs

 

[BlackWorksInc]

This is exactly my experience with Toyota 1000mph; I've noticed they run soft tire pressures for a "softer" feeling ride, I found 36psi on their trucks and BOF SUVs to be a good spec in terms of handling, tire wear, and so on.

 

[STLDAVE]

I did vehicle durability testing for a while. Manufactures run many different tire types at different pressures over thousands of miles. I was fortunate enough to drive some amazing vehicles on many different tire types (snow, AT and performance...etc). Personally, if I'm running a stock tire, then it will be inflated to exactly what the manufacturer recommends. Why? They spend a ton of money figuring out which tire preforms best and at which psi the tire does so while yielding the best results overall (samples were taken 2x a day over 30+ vehicles - this includes psi and tread depth. The vehicles drove 20+ hours a day). Any tire is a compromise - period. Gains in one category loose in another. If you think you can simply inflate your tires and gain mpg without losing in another area then your fooling your self. Do you really think Toyota would accept the current millage of the Runner if all they had to do was inflate the tires and gain +2mpg or more? Poke around the net and you can find pictures of how a given tires "footprint" looks at speed (under inflated and over inflated). Under inflated or over inflated tires will loose a large amount of contact patch at speed while going through snow or water (or normal driving conditions) due to deformation. IMHO if you want better millage then buy an eco tire. If you want the best grip in the winter then buy a winter tire. If you want decent all around + off road, then buy an A\T. There is a ton of real science that goes behind each type, and if there were a tire that did everything, then we would all be fools not to have it.

This all seems reasonable to me. With stock tires, use the recommended pressure for best overall performance.
The real question is, and there are pages and pages of varying opinions on this forum, what pressure should be used with a non-stock tire???