Tire pressure/load questions based on scale weight

[FastEagle]

Originally Posted by Kid Gloves

Michelin recommends sehttps://www.irv2.com/forums/images/editor/separator.giftting tire pressure based on axle loads. Likewise, Roger Marble, aka:Tireman9, also recommends setting tire pressure based on loads on his rvtiresafety.net site.

The USTMA does not disagree until you get below vehicle recommendations.

Inflation pressure recommendations may also be determined based on the tire manufacturer’s specifications, which define the amount of inflation pressure necessary to carry a given load. These inflation pressures may differ from those found on the vehicle tire placard or certification label. However, never use inflation pressures lower than specified by the vehicle tire placard, certification label or owner’s manual. Nor should inflation pressure exceed the maximum pressure molded on the tire sidewall.

REF: page #44 in the link below.

https://www.ustires.org/sites/defaul...uckTires_0.pdf

[Kid Gloves]

As an above average driver, I’ll set the tire pressures for my coach using 4 corner weights and the load and inflation tables. Average and below average drivers may be best served by following the placard pressures.

[rd36mnm]

Originally Posted by Kid Gloves

As an above average driver, I’ll set the tire pressures for my coach using 4 corner weights and the load and inflation tables. Average and below average drivers may be best served by following the placard pressures.

[FastEagle]

Example of a tire rules making committee document. It will show you a little bit about how rules are made/changed.

https://www.federalregister.gov/docu...rying-capacity

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I’d like to see a document that will substantiate that information?

It would not seem likely that a tire expert would disagree with their own industry standards.

[Gordon Dewald]

Michelin, Toyo, Good Year, etc publish tire inflation guides that are likely to include a reserve. Far be it from me to second guess something they publish and add extra inflation to account for intangibles.

Tires are tested at given weights and pressures. It determines sidewall flex, contact area (traction and braking), etc so why would anyone second guess them? Or want to?

[FastEagle]

Originally Posted by Gordon Dewald

Michelin, Toyo, Good Year, etc publish tire inflation guides that are likely to include a reserve. Far be it from me to second guess something they publish and add extra inflation to account for intangibles.

Tires are tested at given weights and pressures. It determines sidewall flex, contact area (traction and braking), etc so why would anyone second guess them? Or want to?

https://www.toyotires.com/media/1496...ntenance_0.pdf

[Kid Gloves]

Originally Posted by FastEagle

Example of a tire rules making committee document. It will show you a little bit about how rules are made/changed.

https://www.federalregister.gov/docu...rying-capacity

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Attachment 340967

I’d like to see a document that will substantiate that information?

It would not seem likely that a tire expert would disagree with their own industry standards.

We can only try to explain how load and inflation tables work. Each individual will need to understand it on their own. The loads and pressures apply to all vehicles, RV’s are not special.

Roger appears to disagree with your interpretation of an industry standard. RV manufacturers don’t know any more about tires than they do about toilets or air conditioners. They just assemble components and in many cases, they don’t do a very good job of that.

Without knowing axle weights, inflating to placard pressure is an uninformed decision. Many folks choose that option.

[wolfe10]

Originally Posted by FastEagle

Example of a tire rules making committee document. It will show you a little bit about how rules are made/changed.

https://www.federalregister.gov/docu...rying-capacity

************************************************** **********

Attachment 340967

I’d like to see a document that will substantiate that information?

It would not seem likely that a tire expert would disagree with their own industry standards.

Don't have documentation, but for many years I presented the "Coach Suspension Seminars" at the FMCA Conventions.


I always asked -- show of hands: many of you have axle weights on your coach/how many of you have individual wheel position weights on your coach?


A very small percent of those in attendance had weighted their coaches. And, from comments, only a small percent even knew it was important.



To the point where I really pushed RVSEF who did the individual wheel position weights at the FMCA Conventions to set up a sign up sheet outside my seminars.

[FastEagle]

I’m a study of tire regulations and standards that pave the way for industry wide safe maintenance and operations. My objective is to use the vast library of information I’ve gathered, to help consumers know and practice the ways things are supposed to happen, or be done to insure their tire knowledge is supported by existing standards and not to make unwise decisions about their tire safety methods.

The first thing to learn about your tires is; who gets to select them. The governing body gives vehicle manufacturers the sole responsibility for Original Equipment tire selections and their fitments. The vehicle manufacturers are directed by the same standards to set recommended cold inflation pressures for all tires they install on a vehicle and to insure those inflation pressures are appropriate for that vehicle. It’s cut and dried with no aftermarket options to lower those minimum standards set by the vehicle manufacturer.

There is a lot of confusion about large commercial tires used on motor homes. Many of those large tire manufacturers follow the commercial tire regulations (FMCSA) and they are not applicable with tires fitted to any vehicle with a final stage certification used for tires fitted in accordance with FMVSS standards.

Optional tire inflation pressures are those set anywhere above what has been recommended and tire sidewall max. The industry wide standard for installing “plus sized” tires is to insure that at the very minimum they MUST provide a load capacity equal to or greater than what the OE tires provide. There are other procedures the installer should insure. The most important is setting a new cold inflation pressure for those plus sized tires.

Tire load and inflation charts are not recommendations. In their creation they were a tool to be used by vehicle manufacturers when setting OE tire recommended cold inflation pressures. They are very important to installers of plus sized tires for that same reason. Tire designated sizes all have individual standardized (TRA) load inflation charts.

That’s it folks, see ya in the next big tire pressure debate.

[Kid Gloves]

Glad that’s cleared up.

I’ll be careful to ensure that my tires are inflated to at least the minimum recommended pressures indicated in the load and inflation table provided by the manufacturer of the tires, based on the known 4-corner weights of the coach.

I can also assure everyone that I did insure the coach.

[Gordon Dewald]

It sounds like "It Depends" is the watchword of the day. Who picks the tires is not that important. I doubt they sit and agonize over each particular brand. More likely the tires size are specified by the engineer to carry a specific load and the purchasing office sends out a RFP to everyone who supplies tires. The lowest bid will likely be the tire selected.

It is sort of like picking oil or gasoline or diesel. Many brands but the bottom line is they all must meet or exceed a given standard. He who supplies the fuel to the bidder is the lowest.