Adjusting tire pressures

[texasrs]

DOMO (I think the single best way to create a virtual social gathering is to put "Tire Pressure" in an RV forum title!)


Domo . . . . you got that right!


Ray

[NXR]

Originally Posted by NXR

My 235/80R22.5 Michelin XRVs are supposed to be at 90. When we were ready to leave Florida in late March it was about 75 degrees. I took the tires to 100 (max sidewall pressure is 110).

When we got back to NE Ohio the temps were about 40. The tires the next morning were in the very low 90's.

I usually keep them about 98 when the morning temps are in the 60's. So far no alarms from the TPMS, which is my goal.

Ray

I just checked them. It's 32 degrees outside and the tires are either 88 or 89 per the TPMS monitor in the house. That's the only way to check tire pressures in cold weather.

So a 43 degree temperature change caused about an 11 lbs psi pressure change.

The usual formula of 2% pressure change per 10 degrees of temperature change seems a bit low for these tires but 2% is definitely close enough for figuring how much to carry.

It's also why I run about 10% over the tire chart numbers as Tireman9 recommends. If I had set the tires to 90 in Florida they would be at about 80 right now. A tire that is 20% under-inflated is considered flat and that would be 72 for me. 80 is a bit too close to 72 for my comfort, especially since tire gauges usually have (roughly) a 3% accuracy tolerance.

90 lbs psi is the sticker number, which is what is needed to support the full GAWR on each axle. We're not quite that heavy but I still use the the sticker pressure as the minimum for a bit more margin. And yes, it rides fine now that we've replaced the stock Ford Sachs shocks with Koni FSD's.

Ray

[Dutch Star Don]

Originally Posted by Ivylog

D * Don, you know I can check my tire pressures while sitting in the driver’s seat by pressing a button on my TPMS. I do this every morning while the rig is airing up, not outside at night.

As usual, you have some inappropriate answer to something different than what was being discussed. People with average reading comprehension know I was discussing those that check their tires with an air gauge, since I was discussing a 45 year time frame, before TPMS was even invented.

Yeah, many of us have TPMS, not just you, and can NOW check their tires via the TPMS system.

[grindstone01]

Originally Posted by NXR

I just checked them. It's 32 degrees outside and the tires are either 88 or 89 per the TPMS monitor in the house. That's the only way to check tire pressures in cold weather.

So a 43 degree temperature change caused about an 11 lbs psi pressure change.

The usual formula of 2% pressure change per 10 degrees of temperature change seems a bit low for these tires but 2% is definitely close enough for figuring how much to carry.

It's also why I run about 10% over the tire chart numbers as Tireman9 recommends. If I had set the tires to 90 in Florida they would be at about 80 right now. A tire that is 20% under-inflated is considered flat and that would be 72 for me. 80 is a bit too close to 72 for my comfort, especially since tire gauges usually have (roughly) a 3% accuracy tolerance.

90 lbs psi is the sticker number, which is what is needed to support the full GAWR on each axle. We're not quite that heavy but I still use the the sticker pressure as the minimum for a bit more margin. And yes, it rides fine now that we've replaced the stock Ford Sachs shocks with Koni FSD's.

Ray

My goal is for the operating/running tire PSI to be at 10-15 PSI over the cold rated psi as marked on the tire sidewall. With TPMS, I can set the morning psi according to the day's temperature and have been able to keep the operating PSI pretty consistent. This can range from starting out at 95 PSI on hot days to 105 PSI for cold days inorder to maintain the approx 120 operating PSI. With TPMS, it's easy to monitor the tire operating PSI.

[Busskipper]

Originally Posted by Dutch Star Don

As usual, you have some inappropriate answer to something different than what was being discussed. People with average reading comprehension know I was discussing those that check their tires with an air gauge, since I was discussing a 45 year time frame, before TPMS was even invented.

Yeah, many of us have TPMS, not just you, and can NOW check their tires via the TPMS system.

I'm one of those who still kicks the tires before he starts in the AM - sorry has worked for well over 50 years Managed to make it to Mid 70's without TPS and well just would really rather be able to hear and feel those tires that are so critical to My Safety, than rely on something - Made in China -

But The part that is Critical is that You the Driver Check the Tires - Both of you DO!- really does not matter how, IMHO, the issue, is if you have made it this far - what you are doing works, at least for You.

If when you check the tires and the pressure has "Significantly Changed" if it has then it should be attended to, sooner than Later.

The pressure thing will be debated till the end of time - and still not resolved or ever will be resolved, again, JMHO. Again for Me I am a wear guy, no matter what the pressure recommended if the tire is not wearing evenly then - - it's not Correct, once again IMHO.

I have run Michelins on all my Cars and Most of my Motorhomes for the last 30 years and can normally get 100k out of a set of tires.........did replace the 14 year old Michelins (69K And sold them to/for a Yard Truck $$$) with newer ones because you guys have been telling me for almost 10 years to get them off the Coach that they were ready to Blow.

Sorry think I should have just stayed out of this- But COVID-19 has me spending too much time on the Computer.

-

[Ray,IN]

Originally Posted by ferimonter

I have a stupid tire question. I live in Florida and have my tire pressure set correctly when I leave heading north. The further north I get the cooler the weather and the lower the tire pressure becomes. Do I each morning have to readjust the tire pressure? Same thing coming from the north (cold weather) back to warmer weather. In this case the tire pressures will increase. Do I need to readjust pressures each morning to correct these difference in pressure.
Thanks

NO. Air them up to the Federal Tire Placard inside the MH and you'll be fine. I've returned home from FL many times and never had to add air.

[ferimonter]

I have a 2019 40' Holiday Rambler Navigator. The stickers call for 110 pounds in the front and 100 pounds on the back. I have never had it weighed to establish the correct pressures

[US1]

Originally Posted by Ray,IN

NO. Air them up to the Federal Tire Placard inside the MH and you'll be fine. I've returned home from FL many times and never had to add air.

My placard has the fronts at 70, rears at 60. Tires have not changed size or load rating, just brand.

Going off tire size/weight carrying charts, 65 is the recommended min psi for my tires. This would suggest the placard is suggesting an unsafe 60psi???
But when using the tire charts when inputing my rear axle weights, the psi comes in at below 60, and since 65 is the min recommendation, I would assume 65 is the number to use.

Thus, I run with the tires at 70psi.

[HJLowell]

Hello Ted

Originally Posted by Mr Ted

Just curious what kind of rig you have ? I have a 2014 43ft Revolution and the tire placard says 85 in all 6 of the rear tires ? Does your rig call for such high pres or is it you just fell its necessary ?

Here is my placard.

I have weighed corner's also.
And tag's now and then.

As we have a certified scales on the farm.
It still comes out close to the placard and the tire company chart the way I load the coach.
Which is light.
We have never blown a tire.

[engine103]