Always use FACTORY tire pressures!

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2014 CX-5 Touring
I've seen some incorrect information in here about having to use higher tire pressures when tires with a higher load rating than the factory tires are used. This is absolutely incorrect and could lead to premature tire wear and even loss of grip in certain situations.

A tire's maximum load rating is always for 35 psi inflation pressure, for passenger car normal load rated tires, regardless of tire size, brand or construction. This load rating far exceeds the GVWR for the vehicle, which you should never exceed anyway. Additionally, the weight on the tire, and the tire pressure, determine the size (area) of the tire's contact patch on the road. Changing the weight on the tire, or changing the tire pressure, will change the contact patch area. Tire size has no effect on contact patch area. A wider tire will have a wider contact path, but shorter at the same time, so the actual area of rubber will be the same, given the same tire pressure.

Tire pressures can be adjusted temporarily for certain driving or load conditions, but for normal everyday conditions, you should always go by the manufacturer's recommended tire pressure. Doesn't matter if you use tires with a higher load rating, or a higher max inflation rating, or a different size tire altogether. Always use the manufacturer's specs for normal conditions, which is 34 PSI for 17" tires and 36 PSI for 19" tires. Increasing pressure over factory specs makes the tire contact patch smaller (less grip) and will also wear out the center of the tire prematurely. I had it happen to me 20+ years ago before I knew anything about cars. I ran Plus Two size tires 8-10 PSI higher than the factory tire pressure rating, and the center of the tire wore down after just a few thousand miles.
 
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Totally agree for the most part, and I'll add,,,, A LOT of people believe that the pressure listed on the tire is what you should run....... PLEASE DON'T!!! That is soo wrong!

I disagree with this though, to a point:
Tire size has no effect on contact patch area. A wider tire will have a wider contact path, but shorter at the same time, so the actual area of rubber will be the same, given the same tire pressure.

If this were true then why does Porsche run 305 width tires when they could run 225. But agree that in some cases it's true.
 
Totally agree for the most part, and I'll add,,,, A LOT of people believe that the pressure listed on the tire is what you should run....... PLEASE DON'T!!! That is soo wrong!

I disagree with this though, to a point:


If this were true then why does Porsche run 305 width tires when they could run 225. But agree that in some cases it's true.

Because on sports cars, a wider tire contact patch is desired. On other cars used more in rainy and snowy conditions, a narrower, longer patch is desired.

But the point still remains: a given weight on a tire, and a given tire pressure, produce the same square inches of rubber in contact with the pavement, regardless of tire width. Length and width of the contact patch changes, obviously, with different tire sizes.
 
I've seen some incorrect information in here about having to use higher tire pressures when tires with a higher load rating than the factory tires are used. This is absolutely incorrect and could lead to premature tire wear and even loss of grip in certain situations.

A tire's maximum load rating is always for 35 psi inflation pressure, for passenger car normal load rated tires, regardless of tire size, brand or construction. This load rating far exceeds the GVWR for the vehicle, which you should never exceed anyway. Additionally, the weight on the tire, and the tire pressure, determine the size (area) of the tire's contact patch on the road. Changing the weight on the tire, or changing the tire pressure, will change the contact patch area. Tire size has no effect on contact patch area. A wider tire will have a wider contact path, but shorter at the same time, so the actual area of rubber will be the same, given the same tire pressure.

Tire pressures can be adjusted temporarily for certain driving or load conditions, but for normal everyday conditions, you should always go by the manufacturer's recommended tire pressure. Doesn't matter if you use tires with a higher load rating, or a higher max inflation rating, or a different size tire altogether. Always use the manufacturer's specs for normal conditions, which is 34 PSI for 17" tires and 36 PSI for 19" tires. Increasing pressure over factory specs makes the tire contact patch smaller (less grip) and will also wear out the center of the tire prematurely. I had it happen to me 20+ years ago before I knew anything about cars. I ran Plus Two size tires 8-10 PSI higher than the factory tire pressure rating, and the center of the tire wore down after just a few thousand miles.

Totally disagree with this. I use one thing to determine my pressures, a tread depth indicator https://www.amazon.com/dp/ (commissions earned)More often than not, if I run factory pressures, the outside edges of my tires will wear (underinflation). Not all factory specs are for optimum tire wear, some manufacturers choose ride comfort as the predominant factor resulting in slightly lower pressures. I found over the years that a 2 to 3 lb. bump in pressures gives me a better ride and improved fuel mileage, but more importantly, even tire wear across the tread surface.
You inflated 8 to 10 pounds over and were surprised to find center wear occurring??
 
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This varies by tire design but I also keep the pressure 2-3 high unless the tire center is wearing a lot more than the edges. I had a miata front tire that was probably a bit low seperate from the rim and deflate when I braked hard and turned sharply at the same time to avoid a car that cut into me on dry course concrete. I did not know the tire deflated and it put me into a skid and I spun up against three other cars. Ever quarter panel was bent, car was totaled but I changed the tire and drove the car home with the AC still working.
 
• a couple psi over on all tires at 38 psi on my stock 19" Toyos here

• no traction issues

• even wear across and closing in on 30K miles. I check with my depth gauge ever 3-5K miles. 9.8/32" new and now at 7/32" (Even all around)
 
A tire's maximum load rating is always for 35 psi inflation pressure, for passenger car normal load rated tires, regardless of tire size, brand or construction.
Sorry this statement is definitely incorrect! Maximum load for a tire always happens at maximum inflation pressure. Maximum inflation pressure at P-Metric era was indeed 35 psi. It gradually increased to 44 psi and now 51 psi with newer technology for lesser rolling resistance and better fuel efficiency. If you read the sidewall label nowadays, it'll say "Maximum Load 1,874 lbs @ 51 psi Maximum Inflation Pressure" or "Maximum Load 1,874 lbs @ 44 psi Maximum Inflation Pressure" for tires with 102 load index. In no way the maximum load rating is for 35 psi for either one of these tires!

BTW, if you see the tire pressure recommendation from a Euro car such as VW or BMW, the label will list several different tire pressures under many different load conditions which actually confuses owners and very inconvenient as you'd need to adjust tire pressure all the time!
 
Totally disagree with this. I use one thing to determine my pressures, a tread depth indicator https://www.amazon.com/dp/ (commissions earned)
More often than not, if I run factory pressures, the outside edges of my tires will wear (underinflation). Not all factory specs are for optimum tire wear, some manufacturers choose ride comfort as the predominant factor resulting in slightly lower pressures. I found over the years that a 2 to 3 lb. bump in pressures gives me a better ride and improved fuel mileage, but more importantly, even tire wear across the tread surface. You inflated 8 to 10 pounds over and were surprised to find center wear occurring??
I have exactly the same experience like you and that's why I've always been using 2~3 psi more than factory spec, i.e. 38 ~ 39 psi for my 19" tires on GT. My '98 Honda CR-V has 26 psi factory spec but I have to use 36 psi for tires with 51 psi maximum inflation pressure in order to get even wear! Of course back to 1998 the maximum inflation pressure on most tires was 35 psi. For the same load index of tires now are having 51 psi maximum inflation pressure.
 
I've seen some incorrect information in here about having to use higher tire pressures when tires with a higher load rating than the factory tires are used. This is absolutely incorrect and could lead to premature tire wear and even loss of grip in certain situations.

A tire's maximum load rating is always for 35 psi inflation pressure, for passenger car normal load rated tires, regardless of tire size, brand or construction. This load rating far exceeds the GVWR for the vehicle, which you should never exceed anyway. Additionally, the weight on the tire, and the tire pressure, determine the size (area) of the tire's contact patch on the road. Changing the weight on the tire, or changing the tire pressure, will change the contact patch area. Tire size has no effect on contact patch area. A wider tire will have a wider contact path, but shorter at the same time, so the actual area of rubber will be the same, given the same tire pressure.

Tire pressures can be adjusted temporarily for certain driving or load conditions, but for normal everyday conditions, you should always go by the manufacturer's recommended tire pressure. Doesn't matter if you use tires with a higher load rating, or a higher max inflation rating, or a different size tire altogether. Always use the manufacturer's specs for normal conditions, which is 34 PSI for 17" tires and 36 PSI for 19" tires. Increasing pressure over factory specs makes the tire contact patch smaller (less grip) and will also wear out the center of the tire prematurely. I had it happen to me 20+ years ago before I knew anything about cars. I ran Plus Two size tires 8-10 PSI higher than the factory tire pressure rating, and the center of the tire wore down after just a few thousand miles.

NOOOOOOOOO! The only correct thing here is the contact patch varies with tire pressure.

The placard's pressure applies ONLY to the OEM supplied tires. Other tires, even the same size, May need different pressure, though the placard pressure is a good starting point.
 
Sorry this statement is definitely incorrect! Maximum load for a tire always happens at maximum inflation pressure. Maximum inflation pressure at P-Metric era was indeed 35 psi. It gradually increased to 44 psi and now 51 psi with newer technology for lesser rolling resistance and better fuel efficiency. If you read the sidewall label nowadays, it'll say "Maximum Load 1,874 lbs @ 51 psi Maximum Inflation Pressure" or "Maximum Load 1,874 lbs @ 44 psi Maximum Inflation Pressure" for tires with 102 load index. In no way the maximum load rating is for 35 psi for either one of these tires!

BTW, if you see the tire pressure recommendation from a Euro car such as VW or BMW, the label will list several different tire pressures under many different load conditions which actually confuses owners and very inconvenient as you'd need to adjust tire pressure all the time!

Sorry, you are incorrect. A tire's maximum load is ALWAYS calculated at 35 PSI for light-load or standard-load passenger car tires. Extra Load tires have their maximum load calculated at 41 PSI.

2-3 PSI different than stock is not a big deal. Different tire gauges might have that much error in them anyway. But larger variations like 8-10 PSI higher than stock is definitely NOT recommended.
 
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NOOOOOOOOO! The only correct thing here is the contact patch varies with tire pressure.

The placard's pressure applies ONLY to the OEM supplied tires. Other tires, even the same size, May need different pressure, though the placard pressure is a good starting point.

Given the same tire pressure, a larger tire will still have more or less the same square inches of tread contacting the ground, with some variation with tire compound and tread pattern. So if you want the same amount of rubber on the road as stock tires, you have to run the same pressure. If you want more rubber (square inches) on the road, you have to lower the tire pressure, whether it's stock tires or a larger size.

If you run higher pressure than stock, even on a larger tire you WILL have LESS rubber contacting the road.
 
From TireRack: "35 psi is the assigned "maximum load" pressure for standard load tires and 41 psi is the assigned "maximum load" pressure for extra load tires."

From WorkTruck Online: "The load-carrying capacity of Pmetric tires is rated as either Standard or Extra Load. Standard Load tires are limited by the load that can be supported with a maximum inflation pressure of 35 psi. Extra Load-rated tires are limited to the load that can be carried at a maximum inflation pressure of 41 psi. Generally, a Standard Load tire will not feature a special designation mark, while Extra Load tires will feature an “Extra Load” marking. "
 
From TireRack: "35 psi is the assigned "maximum load" pressure for standard load tires and 41 psi is the assigned "maximum load" pressure for extra load tires."
From WorkTruck Online: "The load-carrying capacity of Pmetric tires is rated as either Standard or Extra Load. Standard Load tires are limited by the load that can be supported with a maximum inflation pressure of 35 psi. Extra Load-rated tires are limited to the load that can be carried at a maximum inflation pressure of 41 psi. Generally, a Standard Load tire will not feature a special designation mark, while Extra Load tires will feature an Extra Load marking. "
Actually your information quoted is all for old US "P-Metric" standard which has 35 psi as maximum inflation pressure for "Standard Load" and 41 psi for "Extra Load" passenger tires. Maximum load for a tire always happens at maximum inflation pressure is a simply physics. With more advanced tire manufacturing technology, newer tires can withhold much higher inflation pressure for lower rolling resistance and better fuel economy. You can simply read your tire label for maximum load and inflation pressure on the sidewall and see what I was talking about. Or you can call or chat with technical support of any major tire companies such as Michelin to verify my statement.
 
My local Bridgestone performance dealer has always recommended 2 - 3 psi above what is on the label on the door jam. Over the years with both Honda and now Mazda, this advice has proven to be true. The slightly higher psi has prevented premature tyre wear with little to no impact on ride comfort. I run my 19 inch Toyo at 38 psi against the 36 psi on the label.
 
From Tirerack.com:

OEM Toyo A23

Toyo A23.jpg

Michelin LTX

Mich LTX.jpg

Same load rating, different pressure.
 
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My local Bridgestone performance dealer has always recommended 2 - 3 psi above what is on the label on the door jam. Over the years with both Honda and now Mazda, this advice has proven to be true. The slightly higher psi has prevented premature tyre wear with little to no impact on ride comfort. I run my 19 inch Toyo at 38 psi against the 36 psi on the label.

Same here, 38psi.
 
I have exactly the same experience like you and that's why I've always been using 2~3 psi more than factory spec, i.e. 38 ~ 39 psi for my 19" tires on GT. My '98 Honda CR-V has 26 psi factory spec but I have to use 36 psi for tires with 51 psi maximum inflation pressure in order to get even wear! Of course back to 1998 the maximum inflation pressure on most tires was 35 psi. For the same load index of tires now are having 51 psi maximum inflation pressure.
I agree. I typically run +2psi unless I'm heavily loaded (long trip) and then I'll bump it up a couple more pounds (+4psi). The key thing is to maintain the offset between front/rear tire pressures as this will effect handling in aggressive situations.


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Actually your information quoted is all for old US "P-Metric" standard which has 35 psi as maximum inflation pressure for "Standard Load" and 41 psi for "Extra Load" passenger tires. Maximum load for a tire always happens at maximum inflation pressure is a simply physics. With more advanced tire manufacturing technology, newer tires can withhold much higher inflation pressure for lower rolling resistance and better fuel economy. You can simply read your tire label for maximum load and inflation pressure on the sidewall and see what I was talking about. Or you can call or chat with technical support of any major tire companies such as Michelin to verify my statement.

At a recent family gathering I checked the sidewalls on all the cars there (yes I know that's kind of strange). 3 minivans, 2 sedans, 2 CX-5's. The tire manufactures represented were Michelin, Goodyear, Continental. Toyo and Bridgestone. The only tire that had a "@" or the word "AT" linking Max Load with Max Press was the Bridgestone. Not much verification there.

I've invited the author of this website: Barry's Tire Tech to stop by and help clarify this subject.
 
Hi,

Barry of Barry's Tire Tech here. Brillo54 emailed me about this on-going discussion and asked a couple of questions. I thought it might be appropriate to jump in and try to answer not only the questions he asked, but any other questions that might come up - and from reading the thread, I might be here a while. So allow me to fill you in on who I am.

I'm a retired tire engineer. I used to work for one the majors - it shouldn't matter who it was. What should matter is if I can provide enough documentation that you believe the data I am providing.

So first: I have a website: http://barrystiretech.com/index.html

I started the website some years ago because I was repeating myself - and I wanted to have a place to catalog all the research I had done in trying to answer questions - and say what I wanted to say - without having to do the same research over and over.

So here's the answer to the question Brillo54 asked me:

First, the way the max load information is displayed on the sidewall of a tire is one of 2 ways:

1) Max Load XXXX, Max Pressure YY

It should be obvious that this does not imply a relationship between the 2.

2) Max Load XXXX at YY pressure

This does imply a relationship - HOWEVER - some tire manufacturers use this second form in an odd way.

Ya' see the max load for a Standard Load Passenger Car tire occurs at 35 psi (36 if the tire is pure metric) - BUT - it is permissible to use 44 and 51 psi as a maximum pressure for these types of tires - and some tire manufacturers will put on the sidewall: Max Pressure XXXX at 44 psi (or 51 psi) and that isn't exactly wrong, but it is misleading.

To make matters more complex, Extra Load Passenger Car tires max out (load-wise) at 41 psi, so those could say 44, 50 or 51 psi.

I have not seen any tires that say Max Load XXXX at Max Pressure YY - but if they exist, I think those are incorrectly stated unless they mean a max of 35 psi for their tires (which is possible). Any tires that say it this way AND say 44 psi or 51 psi max are just flat wrong.

I hope that helps.
 
Hi,

Barry of Barry's Tire Tech here. Brillo54 emailed me about this on-going discussion and asked a couple of questions. I thought it might be appropriate to jump in and try to answer not only the questions he asked, but any other questions that might come up - and from reading the thread, I might be here a while. So allow me to fill you in on who I am.

I'm a retired tire engineer. I used to work for one the majors - it shouldn't matter who it was. What should matter is if I can provide enough documentation that you believe the data I am providing.

So first: I have a website: http://barrystiretech.com/index.html

I started the website some years ago because I was repeating myself - and I wanted to have a place to catalog all the research I had done in trying to answer questions - and say what I wanted to say - without having to do the same research over and over.

So here's the answer to the question Brillo54 asked me:

First, the way the max load information is displayed on the sidewall of a tire is one of 2 ways:

1) Max Load XXXX, Max Pressure YY

It should be obvious that this does not imply a relationship between the 2.

2) Max Load XXXX at YY pressure

This does imply a relationship - HOWEVER - some tire manufacturers use this second form in an odd way.

Ya' see the max load for a Standard Load Passenger Car tire occurs at 35 psi (36 if the tire is pure metric) - BUT - it is permissible to use 44 and 51 psi as a maximum pressure for these types of tires - and some tire manufacturers will put on the sidewall: Max Pressure XXXX at 44 psi (or 51 psi) and that isn't exactly wrong, but it is misleading.

To make matters more complex, Extra Load Passenger Car tires max out (load-wise) at 41 psi, so those could say 44, 50 or 51 psi.

I have not seen any tires that say Max Load XXXX at Max Pressure YY - but if they exist, I think those are incorrectly stated unless they mean a max of 35 psi for their tires (which is possible). Any tires that say it this way AND say 44 psi or 51 psi max are just flat wrong.

I hope that helps.
I have not seen any tires that say Max Load XXXX at Max Pressure YY - but if they exist, I think those are incorrectly stated unless they mean a max of 35 psi for their tires (which is possible). Any tires that say it this way AND say 44 psi or 51 psi max are just flat wrong.
brillo54 saw Bridgestone tires use an "@" and the maximum inflation pressure definitely is NOT 35 psi because you simply can't find a tire in current market still carries old "P-Metric" standard - with the maximum inflation pressure at 35 psi! So you're saying Bridgestone is "flat wrong" with their specs clearly stated on the sidewall?

I just check the tires on a BMW 520D of my brother's as I'm currently not in the States. These factory Good Year Efficient Grip Performance 225/55R17 101W "EXTRA LOAD" tires say "MAX LOAD 825 kg (1819 lbs) 340 kPa (50 psi) MAX. PRESS." Although it doesn't use an "@", the way it worded, it clearly means maximum load at maximum pressure. BTW, it's also different from the wording you suggested in "Max Load XXXX, Max Pressure YY" form which implies they're not related.

From the Tire Rack:

"Additionally, while a tire's maximum load is the most weight the tire is designed to carry, its load carrying capacity at lower inflation pressures is proportional to how much inflation pressure is used. For example, P235/75R15 P-metric sized, standard load (SL) and extra load (XL) tires used on cars would be rated to carry the following loads at the inflation pressures indicated:"
Air Pressure (psi)2023262932353841
P235/75R15 SL154316351753185219402028
P235/75R15 XL15431635175318521940202821052183
its load carrying capacity at lower inflation pressures is proportional to how much inflation pressure is used.
information
Notice that these two old "P-Metric" tires would carry different load index in specification on newer tire standard. The key here is tires load carrying capacity is proportional to how much inflation pressure is used. The more inflation pressure you have on your tires, the more load carrying capacity they have. It doesn't "stop" at 35 psi or 41 psi! This is the simple physics - maximum load and maximum inflation pressure are closely related to each other and that's why they always put together on the tire sidewall and even use an "@" by some tire manufactures.

Here is 2001.5 VW Passat tire pressure recommendation placard for different speed and load conditions. If your theory is correct as the maximum load is always at 35 psi, why VW and many other Euro cars recommend higher than 35 psi tire pressure for maximum load?

pic-6981828435756281753-1600x1200.jpeg


Another example on Toyo A23 225/55R19 99V tire with maximum load 1,709 lbs (@?) 51 psi maximum pressure used on our CX-5 GT, Mazda recommends 36 psi. In your theory each tire at 36 psi carries at least 1,709 lbs maximum load capacity for a 3,500 lbs CX-5, it definitely will be way over inflated and it simply just doesn't add up with your theory!
 
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