A little tire pressure help please

[flynnwalter]

EdB
2Stroker is right. The only way to actually know how much psi is required by the tire company chart is to know how much weight is gonna be on the heaviest corner, and the only way to know that is by having a four corner weighing. Few do, and that probably accounts for a good percentage of blowouts. If you have a corner (as we do) that is significantly heavier than the other side, taking the entire axle weight and dividing it up by the number of tires can leave the heavy side under inflated, which is the leading cause of blowouts. Motorhomes are often not balanced side to side, according to the fellow at Josams in Orlando where our four corner weighing was done. Yet folks continue to claim to "know" what psi is required by simply weighing the entire axle. Yes, four corner weighings are hard to find as they cannot be done on most scales, but without one you are whistling in the dark.

[ImagineIF]

Originally Posted by WeatherTodd

My tire gauges are accurate to 1/10th of 1 psi at 30/60/90/120/150 psi. Its not some some toy that gets tossed around.

My posts most certainly have a contributing factor...

If you want to contribute, how about telling us what model gauge you have? Few gauges even read to .1 psi and I've never seen one that claims that accuracy. Mine, a Matco DT-4, reads to .1 psi with an accuracy of 1.2 psi at a given pressure. At 100-120 psi I find it accurate to just about that.

[wa8yxm]

I agree with the 5PSI over.. Now I have had people insist that all tires on the same axle need to be the same pressure... I also understand the physics of how tires work and fully believe this is 100% false.

Tires on the same WHEEL need to be the same pressure.. Tires on the same AXLE need to be the same SIZE..

Tires are kind of like baloons, the more air you put in 'em the bigger they get (Only not to the same extent) so if one side is heavier than the other thn one side will need more PSI.


So would get the side weights as well as the ones you have (you need a FLAT scale for that.

IF you would like to sit down with an expert, this may cost you oh, around 50 bucks give or take a bit, but RV Safety & Education Foundation has a link to have some folks with portable scales come and weigh your RV. They find a level spot, you meet them there, they have the charts for your tires, And they give you a short course in tire safety.. HOW short may depend on who buys dinner but hey.... (Actually i'm being serious here the longer you spend with them the more you can learn so do not be afraid to buy dinner) they check your tire pressure gauge, they tell you how old your motor home's shoes are and more.

Though the chart shows the MINIMUM pressure for a given load.... Well, To be honest what it shows is the RECOMMENDED. i like to run 5 PSI high, because if I do that I have 5PSI of headroom should it leak slowly.

And all tires leak very very very slowly (if not faster)

[ImagineIF]

Originally Posted by wa8yxm

I agree with the 5PSI over.. Now I have had people insist that all tires on the same axle need to be the same pressure... I also understand the physics of how tires work and fully believe this is 100% false.

Tires on the same WHEEL need to be the same pressure.. Tires on the same AXLE need to be the same SIZE..

Check the Michelin RV tire guide. They say all tires on an axle must be inflated to the same pressure and that pressure is determined by the heaviest wheel position (left or right). I'm not a tire expert, so I'll go with what Michelin states.

[gottawonder]

Originally Posted by ImagineIF

Check the Michelin RV tire guide. They say all tires on an axle must be inflated to the same pressure and that pressure is determined by the heaviest wheel position (left or right). I'm not a tire expert, so I'll go with what Michelin states.

As does Goodyear...

The Inflation Loading - Goodyear RV
(bottom of the page)

I just went through an iteration on this this morning. Then I went out and got my tires as close to my desired inflation as was practical. I jumped in, ran a 120 mile errand, can absolutely say the time was well spent.

[Ted Lambert]

Originally Posted by ImagineIF

The chart is for minimum pressure for a given load. Your left and right weights aren't likely to be the same. Try to find a place to get wheel position weights. Try a moving company. Once you have actual wheel position weights,use the chart and add 5 psi to overcome gauge inaccuracies. Regardless of the tire brand you have the Michelin RV site has a well written document on RV tire pressure and other good information.

Remember under inflation is the leading cause of tire failure. Personally, I run 10+ psi above the chart pressure.

I don't want to scare you but I just had my tires installed and there was a big difference between the tire shops gauge and mine to be exact 20 lbs.
I have the same gauge they use, very expensive and supposed to be accurate. There gauge 10 psi low mine 10 psi over. Even the manager got involved with this one. I got a free gauge for pointing this out to them.
I am going to get a calibrated gauge from a company that does my Torx wrenches. Yes I agree better over than low.

[trabuco]

I had my rig weights taken wheel by wheel since we were full timing. The right front was heavier by 150 lbs and the right rear was heavier by 700lbs. The 700lbs was quite a shock. I now try to load those heavier items to the left side of the coach. I'm running 100 psi in the fronts and 95 psi on the rears for 275/70/22.5.

I had my weights done by Howard and Linda Payne from RVDreams.com they're affiliated with RVSEF.

[GreaTOne65]

Not trying to be grumpy gus, here, fella's, but using tire pressure to compensate for ride, is a fools errand, it's dangerous and foolish.

[az bound]

Originally Posted by GreaTOne65

Not trying to be grumpy gus, here, fella's, but using tire pressure to compensate for ride, is a fools errand, it's dangerous and foolish.

X2