Question about tire pressure

[FishaHallic]

I have a question about tire pressure that has been bothering me.  On the inside of the drivers door frame of my truck there is a plate that says to inflate tires to 35psi which I assumed it meant for the original tires.  I bought new tires a year or so ago and the max psi is 44 and that is what I filled the tires to.  I recently had my truck in for an oil change and I noticed on my paperwork that they lowered the psi on my truck tires back to 35.  I have always kept my tires to max psi figuring that would be best for fuel economy and I have never had any issues with my tires by doing this but now I wonder if I am doing this wrong.  Should I keep them at 35psi  or max psi as stated on tires of 44?

What about trailers, should I fill them to max psi?

Thank you

[apenland01]

Trailer tires should be at or near max listed pressure for maximum load bearing.

Your truck tires are listed at 35, assuming they are stock size and cold tire pressure.  Here in Arizona, we run 37-39 psi depending on ambient temperature.  37-38 if its 80-90 degrees outside, 38-39 if it's over 100 degrees....

[Princeton_Man]

Sounds like you were at Walmart. Walmart and Sams club do that thinking they can avoid liability issues by sticking to the manufacturers specifications. They also won't install anything except the factory size tires or wheels. That sticker on the door doesn't cover anything but factory tires. If you move up to a more aggressive tread pattern, more ply or a LT tire, you have to find the best pressure for your truck (without going over) and every tire is different. I run 10 ply Cooper Discoverer AT3 XLTs on my Ram most of the year. I believe the max pressure is something like 80psi, but if I ran them at 80 psi they'd wear lousy and beat both the truck and me to death. My best ride and fuel mileage comes from running 40 in the front and 37 in the rear. That also works perfectly for towing the Stratos and they wear beautifully. I air them up to 60-65 when I'm towing the camper and loaded down with gear.

[topdsm0138]

From a former mechanic and Engineers point of view, every tire is manufactured differently. They all have different load and speed ratings, which contribute to it's reccommended max psi. 35psi is the MINIMUM that they should be inflated. (This is why majority of shops use 35psi, they did the minimum, so they're covered from liability) I usally inflate the tires to 5psi less than maximum pressure, test drive, then lower the pressure by about 5psi until I see an even contact patch on the tread of the tire. Too much pressure and the center of the tire will wear out and your ride will be really stiff. (Also run the risk of the tire blowing out) Too less of pressure and the outside of the tires will wear faster and cause a bouncy ride. (This now presents the risk of ruining the sidewall of the tire, it's thinnest part, to where it can blow out) So you have to "play" with the pressure until you get a balance between good contact patch and ride. An easy way to do this for non-mechanics, get a large piece of sidewalk chalk and "shade" the tire tread from side to side on the tire. Drive a short ways, then look at that shaded area to see how it's wearing down. You want even wear/disappearance of that chalk across the tire.

Now a saftey tip on too much pressure. Reason I never go over 5psi under the tires max rating, is that as a tire heats up, the pressure expands. EX: My tires are rated at 44psi max. I inflate to 39-40psi. So after a long drive, the tires pressure will be at the max rating until it cools down. Sitting in the hot sun for a while will slightly increase the pressure. And sitting in the cold weather for a while will slightly decrease their pressure.

Sent from undisclosed location -Tiller Mafia

[FishaHallic]

Sounds like you were at Walmart. Walmart and Sams club do that thinking they can avoid liability issues by sticking to the manufacturers specifications. They also won't install anything except the factory size tires or wheels. That sticker on the door doesn't cover anything but factory tires. If you move up to a more aggressive tread pattern, more ply or a LT tire, you have to find the best pressure for your truck (without going over) and every tire is different. I run 10 ply Cooper Discoverer AT3 XLTs on my Ram most of the year. I believe the max pressure is something like 80psi, but if I ran them at 80 psi they'd wear lousy and beat both the truck and me to death. My best ride and fuel mileage comes from running 40 in the front and 37 in the rear. That also works perfectly for towing the Stratos and they wear beautifully. I air them up to 60-65 when I'm towing the camper and loaded down with gear.

I do not get my oil changes at Walmart, I was at the Chevy dealer.  I also run the Cooper Discoverer but mine are RTX with a 44 psi max.

[FishaHallic]

From a former mechanic and Engineers point of view, every tire is manufactured differently. They all have different load and speed ratings, which contribute to it's reccommended max psi. 35psi is the MINIMUM that they should be inflated. (This is why majority of shops use 35psi, they did the minimum, so they're covered from liability) I usally inflate the tires to 5psi less than maximum pressure, test drive, then lower the pressure by about 5psi until I see an even contact patch on the tread of the tire. Too much pressure and the center of the tire will wear out and your ride will be really stiff. (Also run the risk of the tire blowing out) Too less of pressure and the outside of the tires will wear faster and cause a bouncy ride. (This now presents the risk of ruining the sidewall of the tire, it's thinnest part, to where it can blow out) So you have to "play" with the pressure until you get a balance between good contact patch and ride. An easy way to do this for non-mechanics, get a large piece of sidewalk chalk and "shade" the tire tread from side to side on the tire. Drive a short ways, then look at that shaded area to see how it's wearing down. You want even wear/disappearance of that chalk across the tire.

Now a saftey tip on too much pressure. Reason I never go over 5psi under the tires max rating, is that as a tire heats up, the pressure expands. EX: My tires are rated at 44psi max. I inflate to 39-40psi. So after a long drive, the tires pressure will be at the max rating until it cools down. Sitting in the hot sun for a while will slightly increase the pressure. And sitting in the cold weather for a while will slightly decrease their pressure.

Sent from undisclosed location -Tiller Mafia

That's funny you mention blowouts because I have been wondering about the psi issue for a little while although I never really had any tire issues in my 46 yrs of driving.  I meant I never had any tire issues until 2 days ago  when my boat trailer tire blew out and ripped the fender off, I was doing around 70 mph when it happened and luckily I was on an expressway that had plenty of room to pull off and there were no cars behind me.  So that is kinda why I wanted to check on the psi issue once and for all.  I think I mentioned I always kept my truck tires and trailer tire at the cold psi max.....which I will now change and drop them by about 5psi and see how it goes.

[Princeton_Man]

Sounds like you were at Walmart. Walmart and Sams club do that thinking they can avoid liability issues by sticking to the manufacturers specifications. They also won't install anything except the factory size tires or wheels. That sticker on the door doesn't cover anything but factory tires. If you move up to a more aggressive tread pattern, more ply or a LT tire, you have to find the best pressure for your truck (without going over) and every tire is different. I run 10 ply Cooper Discoverer AT3 XLTs on my Ram most of the year. I believe the max pressure is something like 80psi, but if I ran them at 80 psi they'd wear lousy and beat both the truck and me to death. My best ride and fuel mileage comes from running 40 in the front and 37 in the rear. That also works perfectly for towing the Stratos and they wear beautifully. I air them up to 60-65 when I'm towing the camper and loaded down with gear.

I do not get my oil changes at Walmart, I was at the Chevy dealer.  I also run the Cooper Discoverer but mine are RTX with a 44 psi max.

My short answer, if like the way they perform and wear on your truck at 44 psi, I'd stay with it. I run my trailer tires 5lbs below max pressure. 

[FishaHallic]

Thanks apenland01, Princeton_man and topdsm0138, for your advice, I will drop the psi on my truck and wifes car and I will have to check load rating on my trailer tire and go from there with it.                         
                                                                                                                                                 
Thanks again that really helps  .

Dave

[Hobious]

i ALWAYS use the numbers on my door as a jumping off point.  i tend to add a couple of PSI above that and move on with my life.

that door rating is based off the vehicle (weight and payload, etc).  the one on the tire, there is no way they know WHAT vehicle it is going on.  you dont want to over inflate.  bad ride, weird tire wear, and reduced braking distance..are some results.

[Hobious]

the rating on the door jam is the best jumping off point.  there is no way any tire manufacture can imagine WHAT vehicle that tire is going on, so the manufactures take things like vehicle weight into consideration and paste it to our door jams.  vehicles come in so many configurations. 

i adjust from there, according to what i feel the vehicle is doing.  but the numbers on the door jam are never that far off.