Maximum Tire Pressures

[Crasher]

Originally Posted by bpotter

Ok, what is considered COLD air pressure? If it is prior to tire heating from travel you can be all over the map with the pressure before you start out if the sun is on some tires but not others in the morning (inside dual vs. outside dual). Plus, quite a bit of difference starting out at 30 degrees and driving into 100 degrees, or starting at 80 deg and driving into 30 deg weather.

Most tire manufacturers consider 60-65* OAT for a cold check point. I have used that for the past few years, because we are in WI six months and our AZ home is similar for half of the winter season. My steers call for 110 psi and the others are less, I add 5 psi for safety and temperature and altitude variations. I rarely have to add or release pressure. It could get touchy if your tire is loaded to it's max rating.

[1bigmess]

RV Tire Safety: Cold Inflation

[Ray,IN]

Originally Posted by Crasher

I gave the person the model of tire I have along with the size and load I was carrying which is 7300#. She confirmed that 110 psi was the minimum. I have always carried 115 psi cold and just started to wonder if the load was 7830 and the minimum to carry it is 120 psi, what is the maximum that could be used? It was there that she pointed out that the 120 was also the max, however that the pressure could increase up to 150-155 psi when running at 65 mph on a 100* day on asphalt. Maybe I need to get a second opinion. Increasing the cold psi isn't something I'm going to do, but just wondering???

The maximum load is stated on the sidewall. Venturing over that number exceeds the design limits of that tires construction engineering dept.

[windsorbill]

Originally Posted by bpotter

Ok, what is considered COLD air pressure? If it is prior to tire heating from travel you can be all over the map with the pressure before you start out if the sun is on some tires but not others in the morning (inside dual vs. outside dual). Plus, quite a bit of difference starting out at 30 degrees and driving into 100 degrees, or starting at 80 deg and driving into 30 deg weather.

I have a chart that considers 'cold' as 65 degrees. So, for example, you wake up in the morning, before the sun starts beating on the tires, and the outside air temp is 65 degrees, the chart would tell you not to add/subtract any pressure. If Temperature is higher or lower than that, the chart has you adding or deducting pressure.

[Ray,IN]

Cold is defined as being parked for at least 4 hrs., in any ambient temperature. But I forget which tire mfgr. website I was reading, perhaps Goodyear.

[Crasher]

Originally Posted by Ray,IN

The maximum load is stated on the sidewall. Venturing over that number exceeds the design limits of that tires construction engineering dept.

The maximum load stated on the sidewall was never in question. That is clearly stated. The confusing part to me was the popular opinion that the 120 psi stated was the minimum needed to carry the load implying that one could carry more pressure that the 120. I have concluded that for all of the weights below the maximum, the corresponding psi "is" the minimum needed, but when the load is at the tires rated capacity, the minimum and maximum psi are the same. IMHO, this applies to "All" tires including auto and light trucks.

[twinboat]

Originally Posted by Crasher

The maximum load stated on the sidewall was never in question. That is clearly stated. The confusing part to me was the popular opinion that the 120 psi stated was the minimum needed to carry the load implying that one could carry more pressure that the 120. I have concluded that for all of the weights below the maximum, the corresponding psi "is" the minimum needed, but when the load is at the tires rated capacity, the minimum and maximum psi are the same. IMHO, this applies to "All" tires including auto and light trucks.

I agree and believe the minimum, maximum thing is outdated infomation and no longer relevant.

The Feds require a maximum pressure on every tire.

[luqutus]

And so begins a state of confusion begins. I like check and inflate my tires at 70 deg. with no sun hitting any of them. on days after that if it's 30 deg. 100 deg. or any thing inbetween, after that I look for them all to be the same.

[bpotter]

http://www.rvtiresafety.com/search/l...ld%20Inflation

Wow, 1Bigmess, this is some voluminous amount of information.....

[1bigmess]

Well, it comes from a tire engineer that claims forty years in the business. I'll bet he's forgotten more about tires than I'll ever know.

[Ray,IN]

I wonder how some people ever survived this tire pressure issue prior to the TPMS industry?
The air pressure is the minimum because it is the air pressure to support the maximum load rating of the tire. Ever read one of those tire pressure charts?

[Mr_D]

Originally Posted by twinboat

I agree and believe the minimum, maximum thing is outdated infomation and no longer relevant.

The Feds require a maximum pressure on every tire.

Only for tires on vehicles with a GVWR of 10,000#'s or less. It's all laid out on the NHTSA site but it does take some digging to find.

[Tony Lee]

120 PSI. Your maximum and minimum pressure converged when you load a tire to its full design load capability.

Exactly right.