Tire Pressure

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I was told today from a reliable source that you should set your cold tire pressure 4 psi below the max pressure printed on the tire. The owners manual recommendation or any sticker specifications on the car pertain to the original tires that came on the car from the factory and no longer apply. With new replacement tires, go by what the tire manufacturer says. That's what I was told today.
 
I was told Santa Claus was real.

Same size replacement tire air up just as the OEM. Side wall PSI is MAX load allowable safe pressure.
 
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Originally Posted by MParr
Was this a bathroom artist who told you this? Go with what the door pillar sticker says.

That is how to do it.
 
Originally Posted by MParr
Was this a bathroom artist who told you this? Go with what the door pillar sticker says.

That is how to do it.
 
I set my tire pressure based on conditions and my desired fuel economy.

If I have a lot of weight inside, higher pressure,
Want better mpg and tire wear, higher pressure
If I'm driving in mud and slush I have low pressure

The door placards are just the most comfortable pressure and are a compromise, they have nothing to do with tire wear or fuel economy ,
if optimal comfort is your only priority set per the door placard but we all remember the Ford exploder under inflation scandal, the rating may not have your priorities in mind

So if I have 51psi rated tires why not use them as designed? Better firmer cornering, better mpgs and perfectly flat tire wear.
 
Originally Posted by Rmay635703


So if I have 51psi rated tires why not use them as designed? Better firmer cornering, better mpgs and perfectly flat tire wear.


At 51psi you will REDUCE the contact patch of the tire on the road...better cornering not gonna happen and tire will wear prematurely in the center. That "Rating" is the MAX SAFE pressure. Found out by lab testing and written by a lawyer, not a driver.
 
Originally Posted by das_peikko
I was told today from a reliable source that you should set your cold tire pressure 4 psi below the max pressure printed on the tire. The owners manual recommendation or any sticker specifications on the car pertain to the original tires that came on the car from the factory and no longer apply. With new replacement tires, go by what the tire manufacturer says. That's what I was told today.



Somewhat true. The door placard sticker ONLY applies to the OEM tires, in the OEM size. If you have changed your tire brand/size, then the sticker is a guideline. I replaced tires on a car once, and aired up to the door sticker pressure. It was flat out dangerous. Those tires needed an extra 8-10 PSI over door sticker, or it handled terribly.

The PSI listed on the tire is a maximum allowed. When they put that there, they have no idea what car it will be mounted to. Each car is different, and each car requires different pressures based on weight and other factors.
 
Originally Posted by ammolab
Originally Posted by Rmay635703


So if I have 51psi rated tires why not use them as designed? Better firmer cornering, better mpgs and perfectly flat tire wear.


At 51psi you will REDUCE the contact patch of the tire on the road...better cornering not gonna happen and tire will wear prematurely in the center.


Take two identical police patrol cars. Put one car at 30 PSI. Put the other car at 45 PSI. Put them on the police driving obstacle course, with the same driver. The one with 45 PSI in the tires will absolutely smoke, stomp, and out corner the car with 30 PSI in the tires, and have better lap times. Not even close. I know this for fact, as it was demonstrated to us in the police academy, the importance of tire pressure. The 45 PSI car handled very nicely. The 30 PSI car, wallowed all over the place.
 
Originally Posted by bubbatime
Originally Posted by ammolab
Originally Posted by Rmay635703


So if I have 51psi rated tires why not use them as designed? Better firmer cornering, better mpgs and perfectly flat tire wear.


At 51psi you will REDUCE the contact patch of the tire on the road...better cornering not gonna happen and tire will wear prematurely in the center.


Take two identical police patrol cars. Put one car at 30 PSI. Put the other car at 45 PSI. Put them on the police driving obstacle course, with the same driver. The one with 45 PSI in the tires will absolutely smoke, stomp, and out corner the car with 30 PSI in the tires, and have better lap times. Not even close. I know this for fact, as it was demonstrated to us in the police academy, the importance of tire pressure. The 45 PSI car handled very nicely. The 30 PSI car, wallowed all over the place.


But that's at the cost of unoptimal wear on the 45psi tires right? (assuming running them like that causes the center rib of tread to wear out first)
 
Originally Posted by das_peikko
I was told today from a reliable source that you should set your cold tire pressure 4 psi below the max pressure printed on the tire. The owners manual recommendation or any sticker specifications on the car pertain to the original tires that came on the car from the factory and no longer apply. With new replacement tires, go by what the tire manufacturer says. That's what I was told today.


The only thing you were told that is even close to true is the " 4 psi guideline". When a tire is fully warmed up after driving for many miles, it will read about 4 psi higher than cold, non-driven tires. Hence, check your tires after they have had many hours to cool off, preferably in the morning. Go by the sticker on the drivers side door jam (at least in the USA). On rare occasions, if the company issues revised numbers, then they will also issue new stickers that the service dept will affix over the old sticker.
 
Originally Posted by bubbatime
Originally Posted by ammolab
Originally Posted by Rmay635703


So if I have 51psi rated tires why not use them as designed? Better firmer cornering, better mpgs and perfectly flat tire wear.


At 51psi you will REDUCE the contact patch of the tire on the road...better cornering not gonna happen and tire will wear prematurely in the center.


Take two identical police patrol cars. Put one car at 30 PSI. Put the other car at 45 PSI. Put them on the police driving obstacle course, with the same driver. The one with 45 PSI in the tires will absolutely smoke, stomp, and out corner the car with 30 PSI in the tires, and have better lap times. Not even close. I know this for fact, as it was demonstrated to us in the police academy, the importance of tire pressure. The 45 PSI car handled very nicely. The 30 PSI car, wallowed all over the place.


Maybe this was true for the specific car in this specific case. I do not think this holds true in all cases. In some vehicles (cars and motorcycles) that have something similar to a "competition package", they have revised psi guidelines. What I have seen is generally 2 to 8 psi higher than typical recommendations for "high speed or competition use only". Example- Yamaha R1, Corvette, BMW are the examples I have seen.
 
Originally Posted by Reddy45
Originally Posted by bubbatime
Originally Posted by ammolab
Originally Posted by Rmay635703


So if I have 51psi rated tires why not use them as designed? Better firmer cornering, better mpgs and perfectly flat tire wear.


At 51psi you will REDUCE the contact patch of the tire on the road...better cornering not gonna happen and tire will wear prematurely in the center.


Take two identical police patrol cars. Put one car at 30 PSI. Put the other car at 45 PSI. Put them on the police driving obstacle course, with the same driver. The one with 45 PSI in the tires will absolutely smoke, stomp, and out corner the car with 30 PSI in the tires, and have better lap times. Not even close. I know this for fact, as it was demonstrated to us in the police academy, the importance of tire pressure. The 45 PSI car handled very nicely. The 30 PSI car, wallowed all over the place.


But that's at the cost of unoptimal wear on the 45psi tires right? (assuming running them like that causes the center rib of tread to wear out first)


There's other factors involved also like comfort. Plus I'm not sure about how well the rims will handle such a high pressure, some say that the rims are more likely to crack/bend from a high pressure as there's not much give in the tire to absorb potholes.

As others said, it's always go by the the placard on the car. Mine actually has two sets of numbers, one for heavy/high speed and a regular inflation pressure. I just do it a couple more than the regular pressure. Only the car manufacturer knows about the suspension setup of the car, the tire maker has no idea which is why it's just a max inflation pressure.

Ford Exploders had the problem because not only was the pressure set low, people didn't tend to check their tire pressure that often so an under inflated tire at high summer temperatures with questionable tires lead to blow outs. Probably if they had been set at the recommended pressure with good tires, it would have been fine. They just picked the lower end of the range for better riding comfort because otherwise it's a truck frame and it's a rough ride. It's the reason we now have tire pressure monitoring systems so people don't drive around with under inflated tires.

https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=196
 
These Place Card spec for THE TIRE, are there for all tires of that particular size & speed rating FOR THAT vehicle that the Card is attached to.

I always use the Tire Pressure Place Card on the door jamb or glove/storage box(where ever) as my guideline for tire pressure even if I have changed out the OE tires. I also use the place card as a guideline when I tweak my PSI(F & R) to my particular liking which I often do or depending on passengers, load & higher speed travel.
 
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Originally Posted by Reddy45
Originally Posted by bubbatime
Originally Posted by ammolab
Originally Posted by Rmay635703


So if I have 51psi rated tires why not use them as designed? Better firmer cornering, better mpgs and perfectly flat tire wear.


At 51psi you will REDUCE the contact patch of the tire on the road...better cornering not gonna happen and tire will wear prematurely in the center.


Take two identical police patrol cars. Put one car at 30 PSI. Put the other car at 45 PSI. Put them on the police driving obstacle course, with the same driver. The one with 45 PSI in the tires will absolutely smoke, stomp, and out corner the car with 30 PSI in the tires, and have better lap times. Not even close. I know this for fact, as it was demonstrated to us in the police academy, the importance of tire pressure. The 45 PSI car handled very nicely. The 30 PSI car, wallowed all over the place.


But that's at the cost of unoptimal wear on the 45psi tires right? (assuming running them like that causes the center rib of tread to wear out first)


That's a myth based on what bias treads in the 50's did, has nothing to do with radials.

Radial tires do not stretch or balloon.

I have had several cars were I had sidewalls blow prematurely if I followed the door placard bump up pressure and everything wears evenly no more excessive edge wear.
 
Wow!! Lots to comment on:


Originally Posted by Rmay635703
…… So if I have 51psi rated tires why not use them as designed? Better firmer cornering, better mpgs and perfectly flat tire wear.


First, there isn't any difference between 35 psi max pressure tires and 51 psi max pressure tires - or at least, given all the variability between tires, the max pressure listed on the sidewall doesn't relate to how they are designed.

How do I know? Read up on my webpage:
Barry's Tire Tech: Load Tables

Read about "The notes on page 1-34."

Originally Posted by bubbatime
……. The door placard sticker ONLY applies to the OEM tires, in the OEM size. If you have changed your tire brand/size, then the sticker is a guideline......


ah ….. Mmmmm ….. Not exactly.

From a load carrying point of view, tires are standardized, and it doesn't matter who makes the tire, the load carrying ability is the same.

However, this post went on to talk about handling - and what was being experienced is a difference in the way the tires were designed. It was stated as a "safety" kind of thing, but it could be argued that more responsive handling tires are by their very nature more "safe" - but those are also rougher riding.

Plus, the vehicle's spring rates, shock damping and sway bar size all affect those same properties. So does that mean we have to change those every time we change tires?

So I call the vehicle tire placard pressure a specification. One might not like how the vehicle feels or handles at that specification - and that's OK! People may or may not like how the vehicle handles or rides with the OEM tires, springs, shocks, and sway bars. And some folks will adjust the tire's inflation pressure to get what they want. But others will change springs, shocks and sway bars trying to do the same thing.


Originally Posted by bubbatime
……. Take two identical police patrol cars. Put one car at 30 PSI. Put the other car at 45 PSI. Put them on the police driving obstacle course, with the same driver. The one with 45 PSI in the tires will absolutely smoke, stomp, and out corner the car with 30 PSI in the tires, and have better lap times. Not even close. I know this for fact, as it was demonstrated to us in the police academy, the importance of tire pressure. The 45 PSI car handled very nicely. The 30 PSI car, wallowed all over the place.


Sure, highly inflated tires are more responsive. That was an old trick we used to use when road racing on street tires. But that doesn't mean high pressures are better overall. What about the ride? At 45 psi, the car could ride terrible and be so bumpy, the tire would leave the road surface on washboard roads.

Ya' see. It's all a compromise and what one person finds to be optimal so not what another does.
 
How many times have we read such threads?

ALL my driving life I've upped the pressure to 1) accommodate rough roads, 2) foster better fuel mileage.

EX: 30 becomes 34 or 36. That becomes 40 on highways. I check and adjust often. I get perfectly straight-across wear.

Many people say they check and adjust but they don't.

You know the parameters for tire pressures. Get up off your fat veranda and check your pressures.

Don't forget the spare!
 
I'm not sure how extensively the vehicle engineers test for tire PSI recommendation when they post the F:/R: tire pressure on the Place Card. However, I assume they test in more areas than we know or even think about.

I believe that they test for a combination of ride comfort & handling, along with fuel economy and stopping distance and tire *longevity(?). As well as wet & dry traction and some snow/foul weather ability(probably from the tire mfg). And who knows what else or what get the highest priorities? I mean, I know safety is a top priority.

One specific tire pressure, lets say, 32psi, can't give the best for all 8 of the categories I listed. However, I believe that the engineers test for the best combo(or take into consideration from the tire mfg) all 8 areas and probably more areas as well.

Another thing that I often think about is, e.g., if you own/are driving a 4 dr/5 pass sedan, that the engineers when taking into consideration the R: tire pressure, that we as the car owner will have a certain amount of weight in those rear seats and trunk. (Isn't that why we bought the car?). So, the engineers give the R: tires a specific PSI.

And ME for example, I am often the only person in the car with nothing for weight in the back 'cept a full tank of gas. Therefore, I adjust my R: PSI according to the way I drive and my travel. Because the R: PSI that is listed on the Place Card is often too harsh for my liking with me(or wife & I) in the car. So, I lower it 1 or 2 PSI. Typically I keep the F: according to the Place Card however, I may in fact adjust that as well, if it's just too harsh.
 
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Thats a true statement the OP claims. I was also convinced the boogie man, easter bunny, tooth fairy, santa, the planters guy, mermaids all real as well. I go by my own tire psi, the fitting psi for each vehicle for the driving style of each one that wears the tire even throughout the life of the tire with routine rotations. This is usually a 3-5 psi above mfg's recomendations, when towing heavy the truck gets max psi in the rear, 42 while towing average loads. On Monday commuting, back to 38. The fusion usually does best around 36, still experimenting.
 
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