Tire pressures

Topic: Tire pressures (Read 1260 times) previous topic - next topic

Re: Tire pressures

Reply #20 – August 14, 2021, 01:41:16 pm

Quote from: Chuck & Jeannie – August 14, 2021, 12:43:16 pm

If our wheels are "rated at 120 psi" what happens if the tires are inflated to max allowable pressure on sidewall (120 psi COLD) and then the coach is driven for several hours at 70 mph on a day with cloudless sky and 120 degrees F ambient air temp? Is the wheel designed to accommodate the increase in pressure due to heat? How much increase (above 120 psi) is allowable?

YES, both wheel and tire engineers are very familiar with the Ideal Gas Law. The KNOW what PSI change there will be with temperature rises.

Stated pressures are COLD (at ambient temperature before driving).

Re: Tire pressures

Reply #21 – August 14, 2021, 02:00:21 pm

What surprises me when talking about tire safety. Is the speed I see a lot of RVs traveling on the interstate. I assume that they're reducing tire pressures to try to get a better ride but when you do that I would guess that you're also reducing the speed rating of the tire as well. And I've yet to see a 22.5 inch tire for a class A coach speed rated at more than 75 mph. I assume that's a brand new tire at max PSI. For me 65 on the interstate is where I'm comfortable. Driving that speed I have yet to pass another RVer. But I've had plenty of them come by me doing 75+ So it makes me wonder if it was just premature tire failure when I hear about a blowout. Or was it the tire was run too long or too hard? When I used to ride motorcycles and was on a trip with a group of people in Arkansas riding through the mountains. The first thing I did every morning was get a cup of coffee and go check my tire pressure. There was one of the guys in the group that found some amusement in that. And asked me why I was so worried about the tire pressures. I said take a look at this motorcycle and the two little thin tires that are between me and the pavement. Give that some thought. Well about two months later I got a phone call from him he was going down the interstate in Dallas with his girlfriend on the back when he had a back tire blowout. He managed to get it shut down to about 30 miles an hour before he lost control of it. No one seriously hurt just some road rashes to remember it by. He said all I could think about on the ride home was you checking those damn tire pressures. I now do that religiously.

Re: Tire pressures

Reply #22 – August 14, 2021, 02:01:35 pm

From the the Alcoa manual: "Use the tire manufacturer's recommended pressure, but under no circumstances exceed cold tire pressures roll stamped on the wheel."