Tire pressures

Topic: Tire pressures (Read 1148 times) previous topic - next topic

Tire pressures

August 12, 2021, 10:00:58 pm

Going through my pre-trip checklist today and was checking the air pressure on the tires. At what point do you worry about putting air in the tires to get to your desired pressure. All of my tires are within 3 pounds of where I want them to be. Is this a far enough difference that I should put air in them to bring the 3 pounds up for example I have one I want to be 105 And it's 102 now so 3 pounds low. Should I bring them all as close to the desired pressure as I want or is 3 pounds close enough?

Keith

Re: Tire pressures

Reply #1 – August 12, 2021, 10:01:59 pm

The sunny side will be higher . Let er roll.

Re: Tire pressures

Reply #2 – August 12, 2021, 10:06:06 pm

The answer depends on whether you chose to inflate the minimum for your actual weights or have a "safety cushion".

Most add 5-10 PSI to the chart minimum which gives you some "wiggle room".

Re: Tire pressures

Reply #3 – August 12, 2021, 11:04:44 pm

Check your tire gauge to your car TPS system to check accuracy . The newest OE auto systems are very accurate. My gauge reads 4 high at 50.

Re: Tire pressures

Reply #4 – August 13, 2021, 12:14:58 pm

Quote from: wolfe10 – August 12, 2021, 10:06:06 pm

The answer depends on whether you chose to inflate the minimum for your actual weights or have a "safety cushion".

Most add 5-10 PSI to the chart minimum which gives you some "wiggle room".

So said in another way if I were most people and chart said 105* I would put 110-115*?
I have been running 105* in the front toyos because that is what the PO told me he was running, but I found some cat weight tickets today and it looks like 110* is what I need and 5 or 10* more if I want to be like most people which would 115-120. Am I seeing this right? Also does anyone have a uniroyal pressure chart, I can't find it for the drive and tag axle
Toyo 295/75/22.5. Front axle weight is 12600

Re: Tire pressures

Reply #5 – August 13, 2021, 12:19:20 pm

Quote from: Protech Racing – August 12, 2021, 11:04:44 pm

Check your tire gauge to your car TPS system to check accuracy . The newest OE auto systems are very accurate. My gauge reads 4 high at 50.

And get yourself a decent tire gauge that tells its
accuracy. Mine is + or -- 1 lb at 150 PSI.

Re: Tire pressures

Reply #6 – August 13, 2021, 12:57:25 pm

Here is a good video showing what happens with truck blowouts with tires our size. While most are drive or trailer blowouts, the two front blowouts show what can easily happen when a front tire lets go. And these are professional truck drivers, not RV drivers who, in most states, never had to pass any test to climb behind the wheel.

The video showing what to do in case of a blow out is a feel good video with a big rig professional driver just waiting for the explosive charge to blow out the tire. Plus, he is on flat road at the speed limit. Imagine a blow out on a downhill turn.

Another good section of the video is the big rig with all the outside tires blown and still going down the road. Our Alcoa aluminum wheels are forged and bend rather than breaking like most all passenger car aluminum wheels do.

Pierce

https://www.youtube.com/watch?v=wlvy3osALNI&t=13s

Re: Tire pressures

Reply #7 – August 13, 2021, 08:08:20 pm

Hdff, Uniroyal customer service told me to use the Michelin tire chart as they did not know of a Uniroyal chart. FWIW.

Re: Tire pressures

Reply #8 – August 13, 2021, 08:22:02 pm

My Uniroyal's 105 in front, 95 in rears summer. That puts them at 110 on the road front and rears at 100-105. Max is 120

Re: Tire pressures

Reply #9 – August 13, 2021, 08:27:08 pm

Oh no! The dreaded tire pressure again 😬

Re: Tire pressures

Reply #10 – August 13, 2021, 08:57:50 pm

Quote from: bbeane – August 13, 2021, 08:27:08 pm

Oh no! The dreaded tire pressure again 😬

Shouldn't this question, automatically send you to search function, along with the airbag, bulkhead and dinger questions?

Bruce, I almost ask you this as a joke, when I called you this morning.

Now that I got that out of the way, the most important thing to me is, they are all equal. Especially across the back. and done cold. I have lost more tires than I care to mention. This works for me. DOT dates are far more important.

Heat etc. is going to move them all over. just don't overthink it.

Cheers

Re: Tire pressures

Reply #11 – August 13, 2021, 09:12:08 pm

With this year seeing record high temperatures and so many new RVers on the road this summer after being trapped inside for so long, this dreaded topic has perfect timing. While so many old time Foretravel forum members have read about tire pressure many times, we have many new members who may gain some insight into tire maintenance that they may have not be aware of. After all, not much is required in most states to buy and operate an RV. What new member would dream of the amount of damage a blowout can do to a fiberglass coach?

Pierce

Re: Tire pressures

Reply #12 – August 13, 2021, 10:34:17 pm

Here in a few weeks, we will start harvest. The truck tires are aired to 100 pounds and away we go. That's a good place to start with the motorhome also. If you have a TPMS, you can keep an eye on temperature and air pressure changes. That helps. The only difference is that those grain trucks are carrying one hellacious large load.......adjust the motorhome tire pressure to suit your style.

Re: Tire pressures

Reply #13 – August 13, 2021, 10:43:21 pm

Quote from: hdff – August 13, 2021, 12:14:58 pm

So said in another way if I were most people and chart said 105* I would put 110-115*?

That is what the RV Safety group recommends.

Get corner weights as loaded for travel, including people, pets, and plants in their usual positions while traveling. Inflate all tires (cold) on an axle to 5-10 psi above the load/inflation table number for the higher axle end weight. That gives you a safety margin.

Re: Tire pressures

Reply #14 – August 14, 2021, 12:01:00 am

And for those worried about popping a tire, it would take over 200 psi to pop a 295. Since the Alcoa wheels are rated at 120 psi, it would probably bend them before the tire itself exploded. Normally fine to add air unless they have a bulge or other fault. So, pretty safe to maintain your tires by keeping them to the correct pressure. A tire that has lost pressure in storage and has had the weight of the coach on the flat tire should be replaced.

Did anyone see the pressure wave from the big rig blowout backing out of the station in the video? The wave alone did quite a bit of damage. Easy to see that it's not only the flying rubber that does the damage.

My son and I used to make oxy/acetylene bombs out of 2 liter Coke bottles and set them off from about 75 feet. The huge flash was great but then a pressure wave would come at us in an instant. The feeling when it hit was incredible. What a rush.

Pierce

Re: Tire pressures

Reply #15 – August 14, 2021, 01:33:50 am

Smart to weigh the coach. As I read the chart, the Toyo 295/75/22.5 (G rated) single tire front axle setup supports up to a max weight of 12350 @ 110psi (not 12,600). Do you have H rated tires? Also, when weighing coach, were the fuel, water, waste, propane tanks full? empty? Food in fridge, clothes in closet, normal items in the storage bays? I run my coach 10psi over recommended to allow for these and unknown variables: temp variations effect on tire pressure, last minute "people and stuff" to bring. Rides a little rougher but "may also help minimize tire damage" should I be unable to avoid hitting a chug-hole in the road. Below is the table you provided and how I interpreted it. Also, attached are the Michelin and Bridgestone charts should that be of interest to anyone. None of us want tire trouble, especially blowouts. Great question.

Re: Tire pressures

Reply #16 – August 14, 2021, 10:48:31 am

Good post. When you are 40 feet or longer with slides, it does not take much to be really heavy specially on a longer trip with kids, supplies, etc. That and "good ride" pressures may not go together. And if the pressures are lower than mandated in your PDFs, the speed rating is also not applicable.

Pierce

Re: Tire pressures

Reply #17 – August 14, 2021, 12:43:16 pm

Quote from: Pierce & Gaylie Stewart – August 14, 2021, 12:01:00 am

Since the Alcoa wheels are rated at 120 psi, it would probably bend them before the tire itself exploded.

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?

Re: Tire pressures

Reply #18 – August 14, 2021, 01:22:42 pm

My front tires are at 120 cold do to load rating and front axle weight. My H Dunlop's are only good for 6700 lbs. On our trip the pressures reached 137 on several days. I am sure the wheels are rated at the cold temp just as tires are and know heat will raise the pressure.

Re: Tire pressures

Reply #19 – August 14, 2021, 01:32:07 pm

Since Pierce got me curious with his comment, I just went out and looked at our wheels. I can only see the stamped info on the rear outer wheels, but assume all my wheels are the same model number.

My Model No 873003 Alcoa forged wheels say (for radial ply tires) the max load is 6040 and the max pressure is 105. A bit lower pressure than what Pierce mentioned. He must have different wheels.

I'm willing to bet there are some Forum members who are running higher (cold) pressure than that on these same wheels.

I run 100 psi (cold) all around cuz it is 10 psi higher than the Uniroyal RS20 chart calls for at my coach's weight AND is easy to remember. I guess I'm safe.

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."

Re: Tire pressures

Reply #23 – August 14, 2021, 02:14:01 pm

Quote from: Res777 – August 14, 2021, 02:00:21 pm

When I used to ride motorcycles and was on a trip with a group of people in Arkansas riding through the mountains.

Mountains in Arkansas?
Bahahahaha

Re: Tire pressures

Reply #24 – August 14, 2021, 02:31:41 pm

Quote from: Travelin' Man – August 14, 2021, 02:14:01 pm

Mountains in Arkansas?
Bahahahaha

Well. They call them mountains. Who am I to question them? 😂

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