Correct Tire Inflation

[Augustus]

On my 2005 Toy 4Runner I have replaced the original tires with Yokohama Geolander H/T-S P265/65R17 110S tires. They are the recommended tire size.

The sidewall: 51 Max PSI. Toyota manual and dealership recommend 32 PSI. (Why? for a softer ride?) I think that is under-inflated for these tires.

I compromised and get slightly better mileage at 40 PSI but Toyota dealer claims that would eventually wear out the center tread, though I'm concerned (but not overly) that at 32PSI is under-inflated and would hurt the sidewalls?

What PSI would you recommend? And is inflating any tire at its max PSI (51 in my case) too high?

Thanks.

 

[Jason2007]

Id try inflating 36-38psi and see how you like that ride and how the tire wears.

 

[Shannow]

Take your business card, and slide under the edge of the tread.

Want around a half inch to go under. give or take.

 

[CapriRacer]

Here's my standard response on inflation pressure:

**************************************************

On every vehicle sold in the US, there is a sticker – commonly called the tire placard - that lists the original tire size and the proper pressure for that size. The placard is usually located on a doorpost or in the glove box – but sometimes it is located in the trunk or on the fuel filler door.

Personally, I like a car that handles crisply. So I use 3 to 5 psi above the placard pressure. I also get better fuel economy, better wet traction, better snow traction, better tire durability, better tire wear, but I do have a degradation in ride harshness (but I am willing to put up with it.)

BTW, it doesn't matter who makes the tire or what pressure is listed on the tire's sidewall, if the tire size is the same as the placard, then the pressure listed on placard is also appropriate.

One word of caution: Some trucks use tires with the letters "LT" in front of the tire size - and some trucks use tires with the letter "P" in front of the tire size - and some trucks use tires with the letter "C" after the tire size. You should not use "P"'s in place of "LT"'s and vice versa.

You should be sure the pressure on the sidewall equals or exceeds that pressure on the placard. If you do this the issue about the letter "C" in the sidewall will take care of itself (which is not true with "LT"'s vs "P"'s.)

If you are using a tire size that is different than what is listed on the placard, then the pressure has to be recalculated. The calculation is not difficult, but it requires tire load tables which are not allowed to be published in the Internet because of copyright laws. However, I have a copy and would be glad to do the calculation, but the starting point is the vehicle placard: Tire size and inflation pressure. I will also need to know the new tire size.

**********************************************

So since you are using the exact same size as the original, the pressure listed on the tire placard is appropriate.

BTW, if you were to look carefully at the sidewall it will say the MAXIMUM pressure is 51 psi, and that is not a recommendation / specification / etc.

So there's your answer!

 

[HTSS_TR]

Originally Posted By: CapriRacer

Personally, I like a car that handles crisply. So I use 3 to 5 psi above the placard pressure. I also get better fuel economy, better wet traction, better snow traction, better tire durability, better tire wear, but I do have a degradation in ride harshness (but I am willing to put up with it.)


+1

I have 4-6 psi above placard. When I rotate the tires I would measure tread dept and adjust pressure up or down as needed.

 

[Augustus]

Thank you. These are excellent comments and recommendations. I appreciate the time you've all spent.

Another thing that confused me was it appeared these new Yoko' tires had a higher max pressure than the original factory-installed tires. Which made it appear another reason why the 32 psi would be too low. (My placard does state 32psi.)

I can't confirm it, as my records don't indicate the other brand - I think they were BFGoodrich - and the same size.

Would tires made by different manufacturers but the same size have different MAX psi specs? Or are there industry standards requiring tires of the same size to have the same "pressure" specs - other than tread design, material, etc?

 

[wantin150]

I run 225-45-17 on my car. Some mfgs have a max of 44 PSI. Others, a max of 51 PSI. Standard load vs Extra Load for my application. So yes, the max PSI can vary among the same size.

 

[HTSS_TR]

Usually higher speed rate tires have higher max pressure. Most T rate or lower tires have max pressure of 44 PSI or lower, some H rate tires have max pressure at 44 PSI and some have max pressure at 51 PSI. Most V, Z, W and Y rate tires have max pressure 51 PSI.

 

[CapriRacer]

Originally Posted By: Augustus
........
Would tires made by different manufacturers but the same size have different MAX psi specs? Or are there industry standards requiring tires of the same size to have the same "pressure" specs - other than tread design, material, etc?


Short Answer: There are industry standards, but they are a little confusing - even for tire manufacturers.

However, the way inflation pressure and load carrying capacity are related is governed by a series of industry tables - and that's why it doesn't matter who manufactures the tire - the inflation pressure specification remains the same.

Long Answer:

http://www.barrystiretech.com/loadtables.html

 

[eljefino]

Originally Posted By: CapriRacer

If you are using a tire size that is different than what is listed on the placard, then the pressure has to be recalculated. The calculation is not difficult, but it requires tire load tables which are not allowed to be published in the Internet because of copyright laws.


This is interesting. I'm sure I've seen them. I have to imagine, somewhere, some government entity with the force of law, has integrated that table. As law cannot be copyrighted, that table then becomes public domain, when quoted from that law!

On a realistic note, one can find that table, perhaps in accidental copyright infringement.

If that table exists entirely of data stamped into tire sidewalls, one could compile a "wiki" based on what they've seen...

 

[CapriRacer]

Originally Posted By: eljefino
This is interesting. I'm sure I've seen them......


I am sure you have. Bit and pieces have been published on the 'net - some by tire maufacturers, some by tire retailers. But they are still copywrited and officially not allowed to be published.

Originally Posted By: eljefino
....... I have to imagine, somewhere, some government entity with the force of law, has integrated that table. As law cannot be copyrighted, that table then becomes public domain, when quoted from that law!....



What most government entities do is reference the tire standardizing organization as the source - and not publish the entire table.

Originally Posted By: eljefino
.......On a realistic note, one can find that table, perhaps in accidental copyright infringement.....


The current US passenger car table is over 40 pages long - and gets updated every year. Not to mention there are 2 other major tire standardizing organizations, and many small organizations - and each publishes tables. Not all of them have passenger car tire tables though.

Originally Posted By: eljefino
.......If that table exists entirely of data stamped into tire sidewalls, one could compile a "wiki" based on what they've seen...


But the table includes data for tire pressures lower than the "rated" pressure.

Besides, what is printed on the sidewall of tires is this:

Maximum Load
Maximum Pressure

The 2 are NOT necessarily connected!

 

[Augustus]

Originally Posted By: HTSS_TR
Usually higher speed rate tires have higher max pressure. Most T rate or lower tires have max pressure of 44 PSI or lower, some H rate tires have max pressure at 44 PSI and some have max pressure at 51 PSI. Most V, Z, W and Y rate tires have max pressure 51 PSI.


I take it then the 110S indicated for my tires is the S rating up to 110MPH? Not that I'm concerned about going 112MPH per below. (AZ now has freeway speed cameras...)

(I found this chart below on the internet.)

Q= 99 MPH, 160km/h S=112 MPH, 180km/h
T=118 MPH, 190km/h U=124 MPH, 200km/h
H=130 MPH, 210km/h V=149 MPH, 240km/h
W=168 MPH, 270km/h Y=186 MPH, 300km/h
Z=149 MPH, 240km/h and over

 

[wantin150]

The 110 is the load rating. The "S" is the speed rating, 112 mph, IIRC.

And not all high speed rated tires have 51 psi ratings. Eagle RSA V = 44. Eagle F1 A/S W = 44. Older set of Firestone SV50's Z = 44. And many, many more.

 

[HTSS_TR]

Originally Posted By: wantin150
The 110 is the load rating. The "S" is the speed rating, 112 mph, IIRC.

And not all high speed rated tires have 51 psi ratings. Eagle RSA V = 44. Eagle F1 A/S W = 44. Older set of Firestone SV50's Z = 44. And many, many more.


I did not say all high speed rated tires have max 51 psi ratings, I said "Most V, Z, W and Y rate tires have max pressure 51 PSI."

 

[Augustus]

Thank you all for the replies.

 

[wantin150]

Originally Posted By: HTSS_TR
Originally Posted By: wantin150
The 110 is the load rating. The "S" is the speed rating, 112 mph, IIRC.

And not all high speed rated tires have 51 psi ratings. Eagle RSA V = 44. Eagle F1 A/S W = 44. Older set of Firestone SV50's Z = 44. And many, many more.


I did not say all high speed rated tires have max 51 psi ratings, I said "Most V, Z, W and Y rate tires have max pressure 51 PSI."

 

[Kaboomba]

The only way to know the RIGHT pressure is to get on the TRACK and find the one that makes you FASTEST!

P.S. That is actually the only way to find ideal pressure for a particular tire/vehicle combo. Why? You find out how to get performance. You could then add a little pressure to get MPG.

P.S.S. A bunch of trials of 0-100-0 plus skidpad would work, too.

 

[OtisBlkR1]

Originally Posted By: CapriRacer
Here's my standard response on inflation pressure:

**************************************************

On every vehicle sold in the US, there is a sticker – commonly called the tire placard - that lists the original tire size and the proper pressure for that size. The placard is usually located on a doorpost or in the glove box – but sometimes it is located in the trunk or on the fuel filler door.

Personally, I like a car that handles crisply. So I use 3 to 5 psi above the placard pressure. I also get better fuel economy, better wet traction, better snow traction, better tire durability, better tire wear, but I do have a degradation in ride harshness (but I am willing to put up with it.)

BTW, it doesn't matter who makes the tire or what pressure is listed on the tire's sidewall, if the tire size is the same as the placard, then the pressure listed on placard is also appropriate.

One word of caution: Some trucks use tires with the letters "LT" in front of the tire size - and some trucks use tires with the letter "P" in front of the tire size - and some trucks use tires with the letter "C" after the tire size. You should not use "P"'s in place of "LT"'s and vice versa.

You should be sure the pressure on the sidewall equals or exceeds that pressure on the placard. If you do this the issue about the letter "C" in the sidewall will take care of itself (which is not true with "LT"'s vs "P"'s.)

If you are using a tire size that is different than what is listed on the placard, then the pressure has to be recalculated. The calculation is not difficult, but it requires tire load tables which are not allowed to be published in the Internet because of copyright laws. However, I have a copy and would be glad to do the calculation, but the starting point is the vehicle placard: Tire size and inflation pressure. I will also need to know the new tire size.

**********************************************

So since you are using the exact same size as the original, the pressure listed on the tire placard is appropriate.

BTW, if you were to look carefully at the sidewall it will say the MAXIMUM pressure is 51 psi, and that is not a recommendation / specification / etc.

So there's your answer!


agreed: but in layman's terms let me add
#1 your factory recomendations are correct, but observe your load.. if you add say 6-8 hundred pounds and are setting off cross country.. you would be wise to bump your psi up a few pounds to compensate for the added weight and gain a few mpg on the highway..

#2 your in the same car and your looking for traction, dumping down or "airing down" flattens out your tread to increase surface contact, netting you more grip but not in all driving conditions.. you obviously are going to sacrifice corrnering ability.

#3 i almost always run 3-5 psi higher than what the factory recomends just for the added mpg i get, especially in my truck. *Example* factory calls for 30psi in all 4 corners of my factory 20's. When i head 500mi down to the mountains with the bikes in the bed i bump the fronts up to 34-36 psi and the rear up to 38-40psi. I gain mpg and compensate for 800lbs in the bed. WORKS FOR ME. yes the ride is firmer, but i can deal with it for highway trips.

 

[kr_bitog]

Originally Posted By: Augustus
On my 2005 Toy 4Runner I have replaced the original tires with Yokohama Geolander H/T-S P265/65R17 110S tires. They are the recommended tire size.

The sidewall: 51 Max PSI. Toyota manual and dealership recommend 32 PSI. (Why? for a softer ride?) I think that is under-inflated for these tires.

I compromised and get slightly better mileage at 40 PSI but Toyota dealer claims that would eventually wear out the center tread, though I'm concerned (but not overly) that at 32PSI is under-inflated and would hurt the sidewalls?

What PSI would you recommend? And is inflating any tire at its max PSI (51 in my case) too high?

Thanks.


Inflating to max PSI is definitely too high for the recommended tire size and is dangerous on situation where sudden braking is needed.

Use the below link to determine the initial pressure and then adjust down 1 psi or up a few psi to find the best pressure you like.

Tire Replacement Manual

 

[friendly_jacek]

Originally Posted By: CapriRacer
Originally Posted By: Augustus
........
Would tires made by different manufacturers but the same size have different MAX psi specs? Or are there industry standards requiring tires of the same size to have the same "pressure" specs - other than tread design, material, etc?


Short Answer: There are industry standards, but they are a little confusing - even for tire manufacturers.

However, the way inflation pressure and load carrying capacity are related is governed by a series of industry tables - and that's why it doesn't matter who manufactures the tire - the inflation pressure specification remains the same.

Long Answer:

http://www.barrystiretech.com/loadtables.html



Thanks for the link. Although I think I understand how the tire pressure is calculated according to the load, I still don't understand why the max load is capped at 35-36 psi for SL tires while those tires can be legally inflated to 44 or 51 psi. If the tire supports 1500 lbs at 35 psi, it will support easily more or same with less heat and energy loss at 44 psi. I don't buy the promise that the max cold pressure is merely the safety limit for tire mounting as tires are know to withstand at least 150 psi before loosing seal.

Furthermore, every auto enthusiast like yourself can attest that tires inflated to the manufacturer recommended psi under-perform in most regards (except comfort).

This makes me question the old tradition relying on the old load tables as the ideal standard.

This is especially amazing since car makers go to extreme of recommending 0W20 synthetic fluids, yet they overlook obvious fuel savings by going to higher tire pressures such as 44 psi.