Tire pressure and old wives tales.

[InPursuit]

Originally Posted by JManatee

well there you go, Never below recommended pressure but ok above.

I don't see any clear objective statement on what "recommended" means... and I don't think you'll ever get their lawyers to allow the tire makers to provide it either.

So the adding of a few PSI above the recommended helps with temperature change and slight loss of air over night.

I didn't read those statements to mean that.
on the whole.. it is clear as mud.

If I'm reading and interpreting the transcribed statements correctly...

minimum psi = the weight based calculation of the rig relative to the tire characteristics (clearly stated on the sidewall) and *in conjunction with* what restrictions the wheel will have (stamped into the metal)

maximum psi = the psi as it is stated on the sidewall...
regardless of whatever voodoo someone may be using elsewise

obsessiveness = worrying over minor variations in gauge accuracy or daily temperature or altitude changes

common sense = KISS and to do whatever you do in a consistent manner

[CJ7ole]

USE the tire manufacturers inflation tables for your specific tire and weight. There really is no other bona-fide choice and it really can't be any easier.

Wouldn't using the coach manufacturer's plated weight/tire size/inflation be a bona-fied choice presuming you know you are not overloaded?

Any easier? It isn't easy to get to a weigh station at your maximum load, unless it is on your way, it is open, you have as many passengers as you will ever carry, your food pantries are stocked, coach is full of gas and LP and your water, black and grey tanks are as full as you ever expect them to be and so on and so on. I have never found myself in the situation to get weighed at maximum weight, so I stick with the 80 psi Winnebago calculated when they put the DOT required placard in my coach. And I have a gut feel that I don't exceed the carrying capacity that is also on the placard in the closet.

[RickO]

Originally Posted by CJ7ole

Wouldn't using the coach manufacturer's plated weight/tire size/inflation be a bona-fied choice presuming you know you are not overloaded?

Any easier? It isn't easy to get to a weigh station at your maximum load, unless it is on your way, it is open, you have as many passengers as you will ever carry, your food pantries are stocked, coach is full of gas and LP and your water, black and grey tanks are as full as you ever expect them to be and so on and so on. I have never found myself in the situation to get weighed at maximum weight, so I stick with the 80 psi Winnebago calculated when they put the DOT required placard in my coach. And I have a gut feel that I don't exceed the carrying capacity that is also on the placard in the closet.

That's exactly the approach I used on my coach's maiden voyage... and @ 110lbs it nearly knocked the fillings out of my teeth. After getting weighed, the charts indicated that I could/should be at 85 all around. I went to 90 and it works well for me.

[Route 66]

If you don't know the weights, then inflating to maximum pressure is the safest way to go, but you could be putting up with a much harsher ride than necessary.

[CJ7ole]

That's exactly the approach I used on my coach's maiden voyage... and @ 110lbs it nearly knocked the fillings out of my teeth. After getting weighed, the charts indicated that I could/should be at 85 all around. I went to 90 and it works well for me

I suppose that if my placard said 110 psi on tires rated for 110 psi, I too might go to more effort to weigh at a load that I would never expect to exceed, but already being 30 psi under my tire's rated pressure, my coach rides fine, especially with the Koni's that don't make expansion joints feel like speed bumps.

I will say that when I had two new tires replaced, the shop inflated them to 110 psi, after telling them I wanted 80 psi, and the ride was much harsher. Dropped the pressure back and all was fine.

[rdchevelle]

when driving in the southwest during summertime ,towing across the desert, the road temps can get up to 170 degrees.now if your tires are not inflated close to max presuse you are asking for trouble.heat is the enemy of the tire.the lower the air presure the higher the friction to the tire.my coach rides just fine at max air presure and handles alot better.not too mention a little more pease of mind.just my opnion for what its worth.

[RickO]

Originally Posted by rdchevelle

when driving in the southwest during summertime ,towing across the desert, the road temps can get up to 170 degrees.now if your tires are not inflated close to max presuse you are asking for trouble.heat is the enemy of the tire.the lower the air presure the higher the friction to the tire.my coach rides just fine at max air presure and handles alot better.not too mention a little more pease of mind.just my opnion for what its worth.

Hi rdchevelle... I think I know what you're saying. We too spend a lot of the summer bouncing between Phoenix, Palm Springs and San Diego. Are you making the point that the hot road surface will cause your tires to inflate to/above their max pressure even though they were below that temp when "cold"? Or, is your point that when driving in very hot weather we should begin with our tires inflated to their max?

[wa8yxm]

Originally Posted by mudpuppy

I wonder how many blowouts are due to under inflated tires by folks looking for a Cadillac ride from a truck chassis.

You remember the Ford "Roll-a-matics" (Explorers that rolled over too easily) a few years back... They blamed the Firestone tires.

My somewhat trained and experienced opinion is that you hit it on the head.

You see, Ford told owners to run 'em five pounds BELOW what Firestone said they should run. Add to that "new tires, I don't need to check the pressure" and an oil change tech at the last service interval who was too rushed and forgot the tire pressure and instead of 5 psi low you are running,, if you are lucky, 5 psi.

Now add one of Michigan (And many other states) More famous highway features {Voice of Doom Mode} THE POT HOLE {/Voice of Doom Mode} and ... Well... the rim goes straight through the side wall, causing sudden and explosive side wall seperation.. At this point Mr. Yuppie, who is not a vehicle operator, he's a point and shoot driver, Stands on the brakes with both feet (#1 thing on the DO NOT DO THIS list) and... that's all she rolled.

So the answer is MANY


Oh, what should you do when a tire blows? Well, when the tire blows it's a bit late to click the link... but. Click it now

Michelin North America RV Videos and Demos Page

[azloafer]

Originally Posted by azloafer

The link that follows explains yet another way to check for proper PSI in your tires. I tried it and found that I needed to up the pressure on all 6 tires by 10 pounds. I drove about a half mile for this test. Added air and waited for cool tires and then tested again and they checked out fine. Joe

Optimizing Tire Pressure

I neglected to mention that the air pressure I ended up with was 105 in all tires. I used the large sticks of chalk that is sold as kid's sidewalk chalk. It makes a nice wide chalk line. Happy travels, Joe

[Norm4015]

At a Spartan rally I attended a Michelin seminar given by two engineers from Michelin. After the seminar I sat at a table with them and I spread out my motorhome's corner weights and the Michelin chart. The two engineers and I discussed the tire pressures I should run and both engineers told me to add 5 psi to the chart. That is what I had been doing for years and it is what I still do.

My present trip proves it is a good idea to add 5 psi. I started the trip in the deep south and it was 90 degrees the morning I left and when I inflated my tires. As I have driven north the morning temperatures have dropped and now I am only 2 psi over the chart's psi.

If I had set the tires' psi exactly to the Michelin chart I would have to add 1-2 psi to all six tires every morning to keep them at the chart's recommendation due to cooler weather. Since Michelin says to never run under inflated I would be keeping busy inflating and that would be a PITA. By starting out 5 psi over the chart I can run from Florida to Canada and never worry about adding a couple of psi, or releasing a couple of psi every day.

By the way, I run a tire monitor system so I check the pressures from the drivers seat.

[JManatee]

More is always better, right?

[two-niner]

RickO; do you remember your corner weights? Also, do you have the washer/dryer combo?
Two weeks ago in Phoenix (113 degrees) the battery charger shut off and the batteries were overheated. Never had the auto-shutoff come on before.
Anyway, if you still have them, weights please. (ours weighed heavier)

Thanks, Kerry

[chasfm11]

Originally Posted by JManatee

More is always better, right?

No.

But in a dynamic environment (changing carried weight, changing altitude, changing temperature), not being a slave to a fixed way of dealing with it all makes sense, at least to me.

There are recommended daily amounts of vitamins, right? What happens if I get more than the recommendation? Do I die? One could argue that 20x the daily recommendation for Vitamin C is potentially not good for you. But no where in this discussion have we talked about excess like that? Most of the numbers are less than a 10% variance.

[Tireman9]

RVDude
Yes the load formula is NOT linear as far as inflation effect is concerned.
Use the tables.
I think you will find that with very few exceptions the numbers are all the same, be they Bridgestone, Goodyear, Michelin or any other tire mfg.
The best is to get a copy of the table from your manufacture but the others will do untill you confirm with your manufacturer.