Sorry - tire inflation questions.

[Walholler]

This is a perfect example of turning a mole hill into a mountain. I inflate my tires as I see fit and not on someone else's advice, the way I look at it, I am just as smart as the idiot giving the advice. If the tire says max cold PSI is 80 PSI, I first check to see that my rims will withstand that pressure and then inflate to 72 cold PSI, why 72, because here in the deep south tires will heat up while towing, increasing tire pressure by at least 8 PSI. Now if you do not agree with me, frankly I do not give a rats ass.

[babock]

Originally Posted by ependydad

I always go to this post by Roger of RVTireSafety.net (Tireman9 here on FTF) and keep my trailer tires pumped up to the maximum:
RV Tire Safety: "Interply Shear" and other Techno Babble

He actually recommends using the tire load inflation table and adding 10%

[babock]

Originally Posted by JVS04

I weighed the axles separately at the CAT scale.

TT Front Axle. 3060
TT Rear Axle. 2620

I really question those weights. If you have a leaf spring suspension with an equilizer, they should be exactly the same. Time to go retest.

Make sure your trailer is level enough that the equilizer is not hitting the frame on either end.

[jay2703]

Doesn't the sticker on the side of the trailer give the recommended inflation?

[babock]

Originally Posted by jay2703

Doesn't the sticker on the side of the trailer give the recommended inflation?

Yes...for the OEM tires.

[babock]

From Tireman9's website.
RV Tire Safety: Inflation

Example 2: There was a change in tire size AND in Load Range as can happen with the new Goodyear Endurance.
Original tires were ST205/75R15 LR-C and you mistakenly bought ST225/75R15 LR-E
Back to the Load & Inflation table for ST type tires we see that the ST205 is rated to support 1,820# @ 50 psi and the ST225 can now support 2,830# @ 80 psi. This is a 55% increase in load capacity. If the owner were to run the 80 psi as indicated by the tire sidewall the "ride" would probably be hard on the TT. In this case I would not follow the inflation on the tire sidewall. I would suggest that in this case the owner continue to run 50 to 55 psi and enjoy better tire life. In this example the owner expressed concern about running lower inflation than marked on the tire. Some people even incorrectly said that running less than 80 psi would somehow overheat the tire. I pointed out that I saw no problem with running less than the sidewall inflation as long as the actual load had been confirmed with actual scale readings and that there was a good margin of capacity over the actual loading.

[TitanMike]

Originally Posted by jimmarako

I think this is why the confusion and endless debates continue. Who do I listen to.... Goodyear and their publicly posted inflation/load chart, or Goodyear's engineers who should have been the ones who made the inflation/load chart? Goodyear had the whole Mara-bomb set of tires so you would think they would error on the side of caution, yet lower pressures are OK.

Right now I tow at <= 65MPH because my tires are only 72MPH rated. I'll gladly trade 5 gallons of gas to get 40 minutes back and not have to sit in the slow lane with the old ladys, diesel spewing trucks, and other mis-fits who are afraid to drive. Can't afford the GY Endurance yet.

Jim M.

If we could go ask those engineers referred to in a previous post, the ones who run their ST trailer tires at the max pressure shown on tire sidewall, there's a good chance they are using an OE sized tire and load range in which case the max is the specified pressure.

The only time this issue reveals itself is when the user jumps load range by one or two levels. When that happens the proper pressure is the OE's stated pressure. Extra is not bad but full pressure, depending on Load Range Jump could be excessive and decrease the ability of the tire to grip the road among other issues.

As for adding more pressure to conquer sway after jumping up in load range, not really necessary. The heavier tire construction is a lot stiffer and doesn't need to be grossly over-inflated to be stiffened up.

[Hatchee]

This might be useful. It shows that PSI is dictated by load..."The maximum cold air pressure for each axle may vary, depending on their weights"
http://www.rvtirepressure.com/assets..._Inflation.pdf

[TitanMike]

Originally Posted by jimmarako

I think this is why the confusion and endless debates continue. Who do I listen to.... Goodyear and their publicly posted inflation/load chart, or Goodyear's engineers who should have been the ones who made the inflation/load chart? Goodyear had the whole Mara-bomb set of tires so you would think they would error on the side of caution, yet lower pressures are OK.

Right now I tow at <= 65MPH because my tires are only 72MPH rated. I'll gladly trade 5 gallons of gas to get 40 minutes back and not have to sit in the slow lane with the old ladys, diesel spewing trucks, and other mis-fits who are afraid to drive. Can't afford the GY Endurance yet.

Jim M.

The "Marathon" issue was solely poor tire construction and even max inflation wouldn't have fixed it. Materials have to be formulated, mixed, applied properly to prevent their coming apart in use. Many times the actual compounds used in tires cause them to heat excessively thus shortening their lives.

Based on what I've seen in the past and what's being sold today, today's tires are light years ahead of even tires built a dozen years ago.

[babock]

Originally Posted by Hatchee

This might be useful. It shows that PSI is dictated by load..."The maximum cold air pressure for each axle may vary, depending on their weights"
http://www.rvtirepressure.com/assets..._Inflation.pdf

He needs the Goodyear load charts, which he already said he has looked at. Michelin doesn't even make a 15" ST tire.

[babock]

Originally Posted by TitanMike

The "Marathon" issue was solely poor tire construction and even max inflation wouldn't have fixed it. Materials have to be formulated, mixed, applied properly to prevent their coming apart in use. Many times the actual compounds used in tires cause them to heat excessively thus shortening their lives.

Based on what I've seen in the past and what's being sold today, today's tires are light years ahead of even tires built a dozen years ago.

Also, the Marathon tire was a very reliable tire when it was made in the USA. That formula was lost when they moved production to China.

[TitanMike]

Originally Posted by babock

Also, the Marathon tire was a very reliable tire when it was made in the USA. That formula was lost when they moved production to China.

Agreed. Even OTHER Chinese made tires were better.

[jay2703]

The table he is referencing isn't the recommended inflation pressure. The table he is referencing is the maximum weight for the tire at that pressure. By lowering the pressure, you are reducing the amount of weight the tire is capable of supporting. According to Goodyear:

IMPORTANT: It's a common practice for RV owners to lower tire pressure in their search for a smoother ride. This is not only dangerous, it's relatively ineffective, as the difference in ride quality is not significant. When minimum inflation pressure requirements are not met, tire durability and optimum operating conditions are compromised. Tire inflation pressure should always meet at least the minimum guidelines for vehicle weight.

[babock]

Originally Posted by jay2703

The table he is referencing isn't the recommended inflation pressure. The table he is referencing is the maximum weight for the tire at that pressure. By lowering the pressure, you are reducing the amount of weight the tire is capable of supporting. According to Goodyear:

IMPORTANT: It's a common practice for RV owners to lower tire pressure in their search for a smoother ride. This is not only dangerous, it's relatively ineffective, as the difference in ride quality is not significant. When minimum inflation pressure requirements are not met, tire durability and optimum operating conditions are compromised. Tire inflation pressure should always meet at least the minimum guidelines for vehicle weight.

If you are talking about this table, it certainly is the guide for inflation with a given load. These are the minimum pressures for these tires for a given load.

TIRE LOAD LIMITS (LBS) AT VARIOUS COLD INFLATION PRESSURES (PSI) USED IN NORMAL HIGHWAY SERVICE*

https://www.goodyearrvtires.com/pdfs/rv_inflation.pdf

[ependydad]

Originally Posted by babock

From Tireman9's website.
RV Tire Safety: Inflation

Interesting, it totally seems like he's providing contradictory information depending on which article you read. I've sent a note asking for clarification.

[jay2703]

Originally Posted by ependydad

Interesting, it totally seems like he's providing contradictory information depending on which article you read. I've sent a note asking for clarification.

This is probably the best advice that I got out of the linked article:


"This is why I suggest a +10% value for inflation margin over the table minimum number."


I think if you go to the Minimum you risk losing some pressure and being "Overloaded" If you go to the Maximum there could be some adverse affects from rough ride. 10% over is somewhere in the middle where you get the best of both worlds.

[frank4711]

you know the size of your ST Trailer tire and you know the Load use this chart to PICK a PRESSURE to run it is not a test and there is no exact NUMBER ... cover the load +++ a buffer .. I run 76psi on my ST235 80 R16 (max cold is 80) trailer tires and it is way more load than I need for my 8700lb 5th wheel ... use this chart https://static1.1.sqspcdn.com/static...+inflation.pdf ..... If you do more research you will find that the majority of the industry will recommend you run max cold air pressure on the side of the tire ... I am not everyone and neither are others here so you have to decide

[TitanMike]

Originally Posted by jay2703

This is probably the best advice that I got out of the linked article:


"This is why I suggest a +10% value for inflation margin over the table minimum number."


I think if you go to the Minimum you risk losing some pressure and being "Overloaded" If you go to the Maximum there could be some adverse affects from rough ride. 10% over is somewhere in the middle where you get the best of both worlds.

When using a different tire than OE, and having to consult the load/inflation table it's probably best to use the OEM's stated GVWR, add 10-15% to the weight, then find the correct tire pressure in the table for the weight you calculated. Pretty much the same general principle but probably more accurate.

It would also be a good idea to have a scale weight of the vehicle, loaded as you travel with it, to insure you aren't overloading the rest of the "system" (axles, frame, etc).

Doing this nobody is violating any regulation, they are merely assuring that they have more reserve capacity than what the manufacturer provided.

Kind of like using a 3/4 ton truck to carry the same load they used to put in a 1/2 ton.

[babock]

Originally Posted by TitanMike

When using a different tire than OE, and having to consult the load/inflation table it's probably best to use the OEM's stated GVWR, add 10-15% to the weight, then find the correct tire pressure in the table for the weight you calculated. Pretty much the same general principle but probably more accurate.

It would also be a good idea to have a scale weight of the vehicle, loaded as you travel with it, to insure you aren't overloading the rest of the "system" (axles, frame, etc).

Doing this nobody is violating any regulation, they are merely assuring that they have more reserve capacity than what the manufacturer provided.

Kind of like using a 3/4 ton truck to carry the same load they used to put in a 1/2 ton.

Yep...that's what I do.

On my boat trailer, I had to buy load range E because that was all I could get at the time. Trailer could easily use C. I was trying to find D. I figure my max weight, add 20% and use the chart.

[Teetime]

Originally Posted by JVS04

I weighed the axles separately at the CAT scale.

TT Front Axle. 3060
TT Rear Axle. 2620

Just wondering, how many people split the scales to weight front and rear TT axles?

They are so close together, I don't know if I could do that without still having the rear of my TV still on the front scale...

I've thought the suspension would distribute the weight more equally

There is always something to learn on this forum.