Community Forums

az bound · 09-24-2010, 02:30 PM

Lets see; Last monday I had six kids on the bus. Tuesday I had 20. Wednesday there were 15. Thursday back to 20. Friday I had the whole football team and their gear 40 young men. Now on the days that the buss wasn't full I never knew where they were going to sit. I'm spending more time adjusting air than driving. Oh!! I forgot, some days I started out with a full tank of gas, so I have to factor that in. Now Paul T comes along with temp. chart that I hadn't thought about. The kid are going to have to walk because I'm to busy doing all the math. Besides that they'll be late for school if I stop to get a four corner weight check.

The OP asked a very straight question. Is there a need for concern for the increase in pressure as the tire heats up. The answer is still NO.

swampdog2 · 09-24-2010, 03:17 PM

after reading all these opinion's I have decided I have had the wrong air pres.in every tire I have ever owned and I have driven close to a million miles in my life and had 1 blow out (on a new tire with less than 100 miles on it)
I have always run just shy! of the max pres, on the side wall.I guess, I will just keep doing the same old thing.I heard if you do the same thing the same way every time you will get the same result!!!!

ImagineIF · 09-24-2010, 03:27 PM

It may be counter intuitive, but I'm pretty sure cold is whatever that morning temperature is. If that was not true their would be a cold temperature correction factor based on outside temperature or more likely tire temperature.

I prescribed to using the pressure recommended for the heaviest weight I expect to encounter (full tanks and typical load). If the load is less than that I'm still okay. Over inflation up to the maximum cold tire pressure rating is safer than under inflated.

Pairajays · 09-24-2010, 03:35 PM

So, what is cold when talking about tire inflation pressure? I have sent emails to several tire manufacturers and they all say the same thing. Cold is when the vehicle has not been driven for three or four hours. Now, that opens up a big can of worms. Cold could be just about anything depending on where you are and what season. So cold sounds like, tires rested several hours and at ambient temperature. Still leaves the can of worms open. If your tires specify cold pressure to be 100 psi, then you should inflate them to 100 psi, no matter what the ambient temperature is, be it 70 degrees or 100 degrees.

That should get some responses.

Jim

jwomack · 09-24-2010, 04:11 PM

whew! TMI!!!!

Catch and Release · 09-24-2010, 04:15 PM

Quote:

Originally Posted by swampdog

after reading all these opinion's I have decided I have had the wrong air pres.in every tire I have ever owned and I have driven close to a million miles in my life and had 1 blow out (on a new tire with less than 100 miles on it)
I have always run just shy! of the max pres, on the side wall.I guess, I will just keep doing the same old thing.I heard if you do the same thing the same way every time you will get the same result!!!!

Just think what a smooth ride you could have had all these years if you had taken the extra steps of weighing your coach, and setting the tire pressures to the manufacturer's specifications.

TW · 09-24-2010, 04:21 PM

Quote:

Originally Posted by Rick Long

I cannot believe there are so many uninformed people on the forum!! You do NOT go by the MAX on the side of the tire... you do NOT go by the tag by the drivers seat... These are only to help you NOT go to high as in MAX and Suggested as a starting point on the drivers side tag.
WEIGH it and set the pressure according to weight by the tire manufactures specifications chart available at your dealer or on the web.
Do it right and maybe there won't be so many blow outs!!

PS... NEVER add or remove air from a hot tire... CHECK and ADJUST only on a COLD tire

Right on. Well, with my small FORD Chassis I'm pretty well ALWAYS at max. limit. Every trip I go and a scale is closed, I'll drive over and weigh the MH. 4 corners is very easy... I'm pretty even loaded.

TW

az bound · 09-24-2010, 04:46 PM

Here is another scenario to throw in the mix.
My 100 gal. fuel tank is in the rear of my coach. I also have 100 Gal. of fresh water on board with that tank being also on the rear half of the coach. The black and grey tanks are centrally located. Just for the sake of this scenario lets say my fuel and water weigh 8.2 lbs/gal. That equals 1,640 lbs. As the fuel is used and the water is moved forward shifting more weight to the front tires and less on the rear at what point should I adjust the pressure in the tires?
I am being facetious I know but just think about it.

ccook129 · 09-24-2010, 05:49 PM

gross vehicle weight rating (GVWR) is the maximum allowable total mass of a road vehicle or trailer when loaded - i.e including the weight of the vehicle itself plus fuel, passengers, cargo

gross combined weight rating (GCWR) is the maximum allowable combined mass of a towing road vehicle, passengers and cargo in the tow vehicle, plus the mass of the trailer and cargo in the trailer

gross axle weight rating (GAWR) is the maximum distributed weight that may be supported by an axle of a road vehicle

Now with these charts that are included in all rv's like mine P32 Workhorse,means that the manufacture set this from the factory with full fuel,water,and all other liquids,just the way I weigh my rig.Now they also set a tire psi that is the minimum for each the carry in my case 18,000 lb or 21,000 lb with trailer @ 80psi front and 90 psi rear.My GAWR is 6,000lb front and 12,000lb rear,my michelin tires say max pressure of 95lb psi and my accuride rims say max 110lb psi.Fully loaded I run at 4,500lb on the front end,and 10,570lb on the rear,which below GAWR,so for ride and comfort I run no more than 5psi more than the sticker,85 psi front and 95 psi rear.

howie-2005 · 09-25-2010, 04:00 AM

Thanks for all the replys. I'll leave things alone and not let the pressure monitor bother me. By the replys I don't think many use a pressure monitor system. Maybe if I used nitrogen I wouldn't have an issue either. Thanks again for all your replys.
Marty

Ron & Dee · 09-25-2010, 04:31 AM

Don't worry about nitrogen, you already have 78% nitrogen in there.

Ron

Gary RVRoamer · 09-25-2010, 08:38 AM

Quote:

have always wondered about those stickers placed in the coach by the manufacturer. How do they know what weight I have in the coach and how much of the load each tire is carrying.

The tire pressure sticker the coach manufacturer puts inside generally assumes the axle is loaded to its max rated capacity. If your actual axle loads are less than the max (and they often are), then you can probably use lower tire pressure too. That's why weighing the coach is important. If you have not weighed the coach axle by axle, then do not use any less pressure than the sticker recommends.

Ray,IN · 09-25-2010, 12:17 PM

Quote:

Originally Posted by howie-2005

Thanks for all the replys. I'll leave things alone and not let the pressure monitor bother me. By the replys I don't think many use a pressure monitor system. Maybe if I used nitrogen I wouldn't have an issue either. Thanks again for all your replys.
Marty

I have an use a TST TPMS, it does make me aware of how quickly tire pressure will rise when first starting out in the morning, and how slowing down just 5 mph can lower said pressure.
There are many threads on nitrogen in tires. The bottom line is, unless you find a way to circumvent the laws of physics and gas expansion rates, it will not make a difference. What does affect the rate of expansion is the amount of water vapor in the gas/air used. This will be affected by the maintenance schedule and water filter on the air compressor you use to adjust/inflate your tires.

Ron & Dee · 09-26-2010, 04:20 AM

Quote:

Originally Posted by Ray,IN

What does affect the rate of expansion is the amount of water vapor in the gas/air used. This will be affected by the maintenance schedule and water filter on the air compressor you use to adjust/inflate your tires.

This bring up a good question

I use this pump to top off my tires and have always wondered about the amount of moisture I'm putting into my tires

TRUCK AIR 12 volt Heavy Duty Air Compressor - INTHD-300

Here in Florida the humidity is always high and I don't think this pump has any kind of filter for moisture. Over time I wonder just how much water I have added to my tires and how detrimental it is to the tires?

Thanks,

Ron