Dropping tire pressure for better ride

[Kid Gloves]

Originally Posted by 09 harley

Thank you for confirming what I posted. The pressure on the door jamb are for the maximum load capacity of each axle. If the weight is lower then that is where the load tables from the tire manufacturers come into play. It doesn’t make any difference wether you are talking about a Honda Accord or a lunar launch transporter. At max weight you need max pressure. At lower weights you can use lower pressure. Tire temp is affected when you overload for the pressure in the tire. It’s really a combination of science and common sense.
If we dressed for the coldest temperature we would ever experience we would be a little too hot about 98 % of the time. Same with tire pressure. Personally I increase pressure in all tires before a trip and lower when I get home. I ALWAYS weigh at a scale on every trip. It’s easy and they’re free. I don’t like to feel like I’m riding a buckboard when not towing.
The beauty of this topic is that we can all do what we want and we will be happy. I don’t waste my time trying to convert anyone to my way of thinking. I’m all for each person making their own choices based on whatever they use to make that choice. This is for all things not just tire pressure.
This seems to be a topic that comes up continually and people get pretty pumped up. Pun intended.

We can do what we want and be happy. When it comes to determining correct tire pressure, however, there is no “doing what we want” involved. It is probably the simplest thing we can do on a vehicle. There’s hardly any thinking required. Someone else did that for us. There’s no need to convince anyone to anyone else’s way of thinking, unless they’re doing it incorrectly, and believe they are doing it correctly. Then we can explain to them the correct method.

[09 harley]

Originally Posted by Kid Gloves

We can do what we want and be happy. When it comes to determining correct tire pressure, however, there is no “doing what we want” involved. It is probably the simplest thing we can do on a vehicle. There’s hardly any thinking required. Someone else did that for us. There’s no need to convince anyone to anyone else’s way of thinking, unless they’re doing it incorrectly, and believe they are doing it correctly. Then we can explain to them the correct method.

I think there might be a lawyer or two who advised the company of what info to put on the label. I’ll stick with science and common sense.
I wonder how many RV owners inspect their roofs every six months for caulking and other potential leak sources like the manual instructs. That is there for the same basic reason that the pressures are listed on the door jamb. I’ll have to tell my buddy who builds engines for a NASCAR team that he should tell the tire men on the team to just go with the max pressure. He would be laughed off the team. Can’t wait until the next tire pressure question comes up. Almost as much fun as watching the “experts” at the boat ramp back up their trailers. Happy trails to all.

[Kid Gloves]

Originally Posted by 09 harley

I think there might be a lawyer or two who advised the company of what info to put on the label. I’ll stick with science and common sense.
I wonder how many RV owners inspect their roofs every six months for caulking and other potential leak sources like the manual instructs. That is there for the same basic reason that the pressures are listed on the door jamb. I’ll have to tell my buddy who builds engines for a NASCAR team that he should tell the tire men on the team to just go with the max pressure. He would be laughed off the team.

You’d be giving your NASCAR buddy some really bad advice. Where has it been suggested that anyone just inflate to max pressure?

To reiterate, I said the placard pressures are the recommended minimum pressures to support the weight on an axle at the Axle Weight Rating. Check it out for yourself.

Yes, there is science involved. That’s been figured out for us. We don’t need to understand the science in order to weigh the coach and look at an inflation table.

[twinboat]

[QUOTE=Kid Gloves;5689693]

To reiterate, I said the placard pressures are the recommended minimum pressures to support the weight on an axle at the Axle Weight Rating. Check it out for yourself.

QUOTE]

And if anybody paid attention, that should coincide with the tire inflation tables.

A huge automaker lowered the tire pressures on some SUVs for ride comfort.

As the tire failure rollover crashes mounted and UHaul wouldn't rent to owners of them, they changed there ways.

Lawsuits may have swayed them too.

https://www.fordexplorerrollover.com/

[move on]

I remember that. The Ford Firestone Fight. Firestone had defective tires and Ford's Explorer had an unstable design. They both blamed each other for the rollovers and the lawyers made a fortune. One of the central issues was the recommended tire pressure. Ford recommended 26 psi to give the Explorer a better ride. Firestone wanted 30 psi to keep the tires from failing.

[09 harley]

Originally Posted by Kid Gloves

You’d be giving your NASCAR buddy some really bad advice. Where has it been suggested that anyone just inflate to max pressure?

To reiterate, I said the placard pressures are the recommended minimum pressures to support the weight on an axle at the Axle Weight Rating. Check it out for yourself.

Yes, there is science involved. That’s been figured out for us. We don’t need to understand the science in order to weigh the coach and look at an inflation table.

The whole point is that the pressure is what is needed at max axle rating. Most use is not at that level. Life is not complicated and this issue apparently had you very worked up. Sorry to question your opinion.

[jjrbus]

I have not seen hundreds of stickers on door jambs for tire pressure. possibly 15 I would guess that 13 of them listed the max inflation pressure on the sidewall of the tire as the suggested pressure.


There was a tire engineer contributing on occasion, think he finally gave up.

[Johnynorthla]

Sorry, I can’t help wondering why this is even up for debate, other than a newbie asking a question. Like someone said there is science behind all ratings on an RV. If you purposely disregard them then it’s on you, but worse, you could harm someone else, and that is not acceptable!

[THenne1713]

Originally Posted by Santara

max on 225 75 16 is 65 single 80 dual dosen't matter on manf

Sorry, Santara, but WRONG for the LT225/75R16E (E=LOAD RANGE E)= (Common Class-C FORD/CHEVY CHASSIS RV Tire), which is a 80-PSI MAX-TIRE on a 80-PSI Max RIM... There are older C/D Load range tires MAX 65, that were used like on the little Toyota Class-C?

[Kid Gloves]

Originally Posted by 09 harley

The whole point is that the pressure is what is needed at max axle rating. Most use is not at that level. Life is not complicated and this issue apparently had you very worked up. Sorry to question your opinion.

The point of this thread is the correct tire pressure for a Jayco Class C on a Ford E450 chassis. It is a motorhome. It most likely rolls out of the factory at ~12,500lbs. It isn’t ever going to weigh less. Once loaded for fun, it will probably be very close to the GVWR of 14,500lbs.

If an owner has not weighed the coach, it would be reasonable to use the front axle weight rating of 5K lbs and the rear axle weight rating of 9,500 lbs to determine correct tire pressure for each axle. Many motorhomes operate at or near their axle ratings, particularly those on a lighter chassis. These are facts, not opinions.

As a point of reference only, and not a recommendation for anyone, Michelin recommends a tire pressure for a 225/75R-16, of 75psi on single wheel axle with a 5K lb axle load and 80psi on a dual wheel axle with a 9,500 lb axle load.

Tire pressure is much less complicated than life.

[jadatis]

Originally Posted by jadatis

Think I read all the important reactions here.

You can only be shure about the weights after weighing, loaded the way you go on trip, is the best advice given already.

But I yudged that rear can be lower then front, because of dualload behind.

Mayby I missed you giving GAWR's , GVWR, if you give those together with tire-specifications, I can calculate a safe pressure for that, an then it gives a better indication then experiënce advices.

In my only post #39, I tried to keep it simple, but still have not gotten the GAWR's and GVWR yet.

Tirepressure is all to give the tire a deflection, so heatproduction a cycle, that wont overheat any part of tires rubber, when driving the speed for wich it is determined.

But in practice it is made complicated, by several reasons.

Different calculations used in Europe and America, while laws of nature would need same calculation.

Also maxload is not always the same for same sise and loadrange in European and American system. Then question is , what system gives it the right way to laws of nature.

Determing the weight on seperate tires is a tricky part in it all.

Then inacuracies in pressure-reading also plays a part.

Then for fi 90 degr F ambiënt temp a higher pressure is needed then for fi 40 degr F.
Luckyly within a certain range of ambiënt temp, the pressure rises and lowers by itself, when filled advice pressure at 65 degrF.

And I forgot to give some reasons probably.

That Is why my goal is , the highest pressure at wich comfort and gripp is still acceptable. Gives highest reserve to cover all those factors.