Recommended psi verses Max psi.

[ginostats]

The MAx PSI is listed as "Cold" Because : here is an example…you are driving at 55mph on an 80 degree day, the temp of your tires would be in the 130 degree range…you stop and check your tires and find that your one tire is riding at 30 psi when the max cold is 44….so you fill the tire up to 44..with air that is probably not super cold because it is in fact an 80 degree day….Cold tires are usually "cold" at about 50 degrees..and 44 max psi at 50 degrees is the max you should use…if you drive an heat up your tires that are at 44…after a while you will see the gauge up to as high as 60psi or so, But as someone else posted above, about an increase of one psi per ten degrees..it is actually about one percent per ten degrees…so tires at 44 at 500 degrees should babout 50psi at 100 degrees, however, the shape and thickness of tires definitely comes into play in this area, a high performance tire heats up more than a large tread "wrangler" type tire…so in a jeep you may see the psi go to 48-50- where the same psi in a corvette under the same conditions will go as high as 65-70….see next post…

[ginostats]

I made a mistake or two above and am new to this and do not know how to edit LOl..But the point is..If Someone fills to the "Cold" max the new air going in is cold and can only expand so much, at 44 psi as an example, that cold air is the safe limit, that will not cause a heated tire to over expand and potentially blow out..and even though those numbers come with a safety buffer by the manufacturer( you could easily go to 50psi safely) it is best to adhere to the max number or slightly below..HOWEVER the Number on your Car Door for "manuafatuers Suggested PSI" is the lowest you should even keep your tires inflated…This Number is in direct contrast too the Tire Number..the carmaker number is about smooth ride and comfort, and does not care about tire care and fuel milage…While the Tire Makers, does not care about comfort and leans toward tire wear and safety and file mileage…Here is the BEST BET..Lean Towards the TIREMAKERS NUMBER…if the door says 33 and the tire says 44….go to a middle number and add 2 pSi so the mid number of 33-44 would be 38.5 add two and you got 40.5… level it off to 40 and you have the best possible combination, of Ride, Handling, Tire wear, tire Safety, and Fuel Mileage !

[shorod]

Although the "max pressure" listing on the tire sidewall is irrelevant as long as the tire is the correct size and load rating as the vehicle calls out. The tire inflation should always be per the vehicle door sticker, not the max pressure listed on the tire sidewall.

-Rod

[CapriRacer]

I hope everyone realizes this is an 11 year old post that has been revived.

But I do want to correct one thing that was said.

Originally Posted by ginostats

......... HOWEVER the Number on your Car Door for "manuafatuers Suggested PSI" is the lowest you should even keep your tires inflated…This Number is in direct contrast too the Tire Number..the carmaker number is about smooth ride and comfort, and does not care about tire care and fuel milage…While the Tire Makers, does not care about comfort and leans toward tire wear and safety and file mileage…...

The max pressure listed on the sidewall of the tire is just that - a maximum. It does not take into account anything about the vehicle. It is like saying you have a pickup truck that can haul 3,000 lbs. That only means that is the maximum allowable, not a recommendation for everyday usage.

Further, the number the car manufacturer put on the vehicle tire placard, may or may not be be strictly for comfort. It depends on what the vehicle was designed to do. Sometimes these pressures are biased towards handling - sometimes not. In the case of pickup truck, the inflation pressure is set to carry the load in the bed and ride and handling come secondary.

And lastly, the combination of tire size and inflation pressure determine the load carrying capacity. Some vehicle manufacturers will specify a large tire to get a low pressure (so they get a soft ride). If you put the max pressure in the tire, you could wind up with half the size of the footprint - and that causes traction problems.

[RidingOnRailz]

Earlier this month, I posted a poll about where people get their tire pressure info from, before realizing that this Tire and Wheel subforum existed. It got very few responses, but the majority of those that did vote said they went by the vehical load decal.

I'm sure none of those respondants were mechanics, as most mechanics and service techs I have used lately inflate at or just below the Max. Cold number on the tire itself!

This concerns me, since many mechs. I know do have ASE on their work shirts, and should know which numbers to inflate to. I would expect this from the public, since the vast majority of the public still don't know where the correct recommended cold tire pressures are posted for their specific vehicles.

I'm sure my poll would have gotten more votes here, so I will ask here:

What source do you refer to when inflating/adjusting your every day vehicle cold tire pressures?

[CapriRacer]

Like you, I am puzzled over why mechanics don't know about the vehicle tire placard - except to say, they probably got their information from their fellow workers, and that's not always a reliable place to get correct info.

Having been a tire engineer for over 40 years, I know where both sets of numbers come from and I know that what is printed on the sidewall is relatively arbitrary. See my webpage on the subject of load tables :

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

About 1/3 of the way down, I talk about "The Notes on page 1-34" and that is where the sidewall number comes from.

[RidingOnRailz]

Originally Posted by CapriRacer

Like you, I am puzzled over why mechanics don't know about the vehicle tire placard - except to say, they probably got their information from their fellow workers, and that's not always a reliable place to get correct info.

Having been a tire engineer for over 40 years, I know where both sets of numbers come from and I know that what is printed on the sidewall is relatively arbitrary. See my webpage on the subject of load tables :

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

About 1/3 of the way down, I talk about "The Notes on page 1-34" and that is where the sidewall number comes from.

Well, the owner at the place that recently did my brakes responded to my question about the importance of the load decal with "The pressures on that sticker are a joke" "I always set tire pressure to a pound or two under what's on the tire - The handling is way better"

So these mechanics - and many customers - do know where the correct cold pressures specific to a vehicle can be found. They just choose to do things their way instead of the right way, or at least by what is recommended. And it probably extends to other things in their lives beyond the air pressure in their tires.

[Stealthee]

That owner is a moron. There is no way it handles better with more pressure. It goes against the laws of vehicular physics.

I got into an argument with a guy at work about this exact same issue a few weeks back. He tried to say you always run max psi and I told him he was an idiot. He tried to tell me me knew better than I did because he used to sell tires.

Just because one sells/installs tires doesn't mean they know anything about tires.

[RidingOnRailz]

Originally Posted by CapriRacer

Like you, I am puzzled over why mechanics don't know about the vehicle tire placard - except to say, they probably got their information from their fellow workers, and that's not always a reliable place to get correct info.

Having been a tire engineer for over 40 years, I know where both sets of numbers come from and I know that what is printed on the sidewall is relatively arbitrary. See my webpage on the subject of load tables :

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

About 1/3 of the way down, I talk about "The Notes on page 1-34" and that is where the sidewall number comes from.

Where are the complete load tables? My size is not listed there: 195/65R15

[RidingOnRailz]

Originally Posted by Stealthee

That owner is a moron. There is no way it handles better with more pressure. It goes against the laws of vehicular physics.

I got into an argument with a guy at work about this exact same issue a few weeks back. He tried to say you always run max psi and I told him he was an idiot. He tried to tell me me knew better than I did because he used to sell tires.

Just because one sells/installs tires doesn't mean they know anything about tires.

I think your conversation with that person became an argument after the name-calling began. If on the other hand he first called you a name, then I would have responded with "This conversation is OVER if it degrades to name-calling", and then walked away.

I can't believe this tire pressure thing is taken more personally, by some, than politics and elections! Sheez..

[CapriRacer]

Originally Posted by Stealthee

...…. There is no way it handles better with more pressure. It goes against the laws of vehicular physics. ……

Not exactly. Using a higher inflation pressure makes the tire respond quicker to steering input. If that's what is being used as the definition of "Handling", then the statement is correct.

Originally Posted by RidingOnRailz

Where are the complete load tables? My size is not listed there: 195/65R15

The tables are published in a yearbook issued by the various tire standardizing organizations. They are copyrighted and can't be reproduced without permission.

However, you can find abbreviated versions if you search on the term "Tire Load Tables". Just be aware that each standardizing organization uses a SLIGHTLY different formula, so the values will be SLIGHTLY different - close, but different. I've found one for passenger car tires from Toyo, and I am sure there are others.

Originally Posted by RidingOnRailz

…..I can't believe this tire pressure thing is taken more personally, by some, than politics and elections! Sheez..

Been in the business over 40 years and it's always been like that.

[RidingOnRailz]

Originally Posted by CapriRacer

Not exactly. Using a higher inflation pressure makes the tire respond quicker to steering input. If that's what is being used as the definition of "Handling", then the statement is correct.



The tables are published in a yearbook issued by the various tire standardizing organizations. They are copyrighted and can't be reproduced without permission.

However, you can find abbreviated versions if you search on the term "Tire Load Tables". Just be aware that each standardizing organization uses a SLIGHTLY different formula, so the values will be SLIGHTLY different - close, but different. I've found one for passenger car tires from Toyo, and I am sure there are others.



Been in the business over 40 years and it's always been like that.

Well, it's science and engineering, nothing personal. People shouldn't get so worked up over it or think they know better than those that designed and built the vehicle.

[RidingOnRailz]

My 2015 base Elantra sedan, OEM T-rated 195/65R15, calls for Fr/Rr 33psi cold. For the 2011-13 of that same trim level, Fr/Rr 32psi is specified.

At 33psi cold to all four corners, my Elantra accelerates fine, gets mid-20s to mid-30s MPG gas mileage according to the gauge cluster, but handles/rides nervously and a little rough over gravelly, bumpy roads. I experienced this both with the Kumho stock tires that came on the car, and with the True-Contacts I had installed two winters ago and am still riding on.

Cutting the rear tires back to 2011 pressures(32psi cold), tames some of that rear hop and there is no hit on that indicated gas mileage.

Cut to 2011 pressures all around, and this 2015 Elantra feels like a CAR again: nicely weighted steering even in Normal steering mode - and that rear end minds its business. I still use Sport mode on highways, for maximum steering weight. Avg. mileage does suffer a bit though at those pressures, with city falling to low 20s, and highways around 30mpg.


In retrospect: This Elantra, with 32 all around psi, out-handles the 2013 Sonata LTD I traded for it. That Sonata, with its wider 55-series 17s set even at 33psi, and history of 'self steering' issues - particularly on first through third model years of that body style - steered lighter in the dealer-set Sport mode than my Elantra set for COMFORT! It was a white-knuckle experience on highways, esp. after dark, and after dark plus raining. I just could not feel where the car was in its lane!

Not to mention on my specific Sonata the Caster angle was equally half a degree below the minimum range for some reason(previous driver mounted a curb at 30mph by mistake??). That was not adjustable unfortunately. I do miss the moonroof though: turns any car cabin into a cathedral!

Verdict: If acceleration and one-finger Tom Cruise-maneuverabilty matter most to you, go with wider lower profile tires. But for myself, and many others, higher narrower profile tires at modest pressures keep things tight on the straight and narrow. And we don't mind using actual muscle to turn the steering wheel. ;D