Tire Inflation Chart

[Ski]

Checking to see if I'm reading the Michelin tire inflation chart correctly.

 

Weight on the front axle is 8,000lbs. Inflate to 85lbs.

Weight on rear axle dual wheels 15,000lbs. Inflate to 80lbs.

 

I'm using these maximum weights until I have to motorhome loaded and weighed at a scale.

 

XRV 235/80R22.5 G

 

Using a weight of 4,000lbs per front tire inflate to 85lbs.

Using a weight of 7,050 per side dual rear wheels inflate to 80lbs.

 

 

http://www.michelinrvtires.com/reference-materials/load-and-inflation-tables/#/

 

Thanks,

 

Al

[Newt]

Until you get individual wheel weights, it's best to go with the max.

 

Newt

[NoDirectionHome]

Yes, you are reading and interpreting the chart correctly

[mptjelgin]

My understanding is that the correct approach is to take the first inflation pressure that exceeds your measured weight, and then add some amount (10 psi, or 10%) to take into account unknowns like side-to-side variation, load shifts over time, etc.

 

So for the front axle you need 4000 pounds. I'd start with 90 psi (4140 pounds) since 85 psi does't quite make it (but it's close) and then add the safety factor of 10 psi. So I'd be using 100 psi on the fronts.

 

For the rear you actually have 7500 pounds (not 7050) if your total weight is 15,000. So I'd start at 90 psi (7530 pounds) and add 10 psi, so again I'd be at 100 psi.

 

As Newt mentions getting a true individual wheel weight is preferable, but it is still recommended that you add the extra for a factor of safety.

[Smitty77_7]

My understanding is that the correct approach is to take the first inflation pressure that exceeds your measured weight, and then add some amount (10 psi, or 10%) to take into account unknowns like side-to-side variation, load shifts over time, etc.

 

So for the front axle you need 4000 pounds. I'd start with 90 psi (4140 pounds) since 85 psi does't quite make it (but it's close) and then add the safety factor of 10 psi. So I'd be using 100 psi on the fronts.

 

For the rear you actually have 7500 pounds (not 7050) if your total weight is 15,000. So I'd start at 90 psi (7530 pounds) and add 10 psi, so again I'd be at 100 psi.

 

As Newt mentions getting a true individual wheel weight is preferable, but it is still recommended that you add the extra for a factor of safety.

 

 

This seems reasonable, and safe, until you can get your actual four corner weights, and then add 10% PSI on top of that. I personally, round up to the next 0 or 5 ending number... as it is just easier to remember.

 

We had a classic example of why the contingency today. We drove for about 4 1/2 hours with a seemingly never ending side cross wind coming towards the Driver's side of the coach. So in addition the crown of the road shifting some weight, the side cross winds also added a good load onto the passenger side of the coach:)!

 

Best to all, travel safe, have fun,

Smitty

[Guest jammyjameson]

Yes, thats the best option

[Alie&Jim's Carrilite]

Something to consider on the front axle. Run at least the minimum pressure, but depending on how the steering feels- mushy, squirmy, wandering, unstable, adding air pressure usually makes the steering feel tighter. But too much air can make it a very hard ride.

[oldjohnt]

Of course, knowing the actual weight is best and then consult the manufacturer tire charts WELL DUH but if I don't know the actual weight, in the meantime until I find it, I look at the tires MAX LOAD at X PSI, and use that temporarily. If I had to bet money or for safety sake, I would err on the side of OVER (up to Max Load at X PSI) versus UNDER inflation, which flexes the sidewalls and generates heat, a tires enemy. I'm NOT a big fan of the sealing method/reliability of either the Crossfire type product or the flexible extenders to make checking and airing easier, but that's fine for those who like them, until such time I choose to use them (which I may or may not) I'm "considering" carrying just a tad more initial PSI in the slightly cooler outer dual then the warmer inside dual and check air pressure and tire temperatures often at rest and fuel stops. Sure, electronic air pressure monitors are another method for those who choose their use, to each their own. I've NEVER wore the tread off a set of RV tires (even if over inflated), but change them after 5 or 6 years anyway just to be on the safe side

 

John T NOT a tire expert so do what tire companies say NOT me.

[Grassy]

I am thinking there is a theory / reality gap here..

 

I did this route... I was running 245/75 22.5 Goodyears at the time..weighed the Tv ..factored in the pin weight.. set tire pressures accordingly. TV unstable at best. Went up to 80 psi and the rig felt fine with or w/o the trailer.

 

Shopped for new tires this year.. was told by every truck tire dealer that I was nuts running any pressure below 90 psi regardless of my weight. Their theory is under 90 psi, the tire is under pressure..which creates heat..which destroys the tire...etc..

 

Settled on Michelin 235/80 22.5.. got the same lecture ..so I am 90 psi.

 

Had this same discussion with another member and he said I was over inflated.. so, I e-mailed Michelin to asking to clarify weather I should follow what I am being told at the truck shops or should I go by their guide.

 

It has been over a month and no response.

 

Has anyone had correspondence with Michelin (or other brands) stating that is ok to run under 90 psi ?

 

Thanks.. inquiring minds want to know

[Ray,IN]

Grassy, you'll not find any tire manufacturer that will recommend less air pressure than what the vehicle mfgr. recommends.

Checking to see if I'm reading the Michelin tire inflation chart correctly.

Weight on the front axle is 8,000lbs. Inflate to 85lbs.
Weight on rear axle dual wheels 15,000lbs. Inflate to 80lbs.

I'm using these maximum weights until I have to motorhome loaded and weighed at a scale.

XRV 235/80R22.5 G

Using a weight of 4,000lbs per front tire inflate to 85lbs.
Using a weight of 7,050 per side dual rear wheels inflate to 80lbs.


http://www.michelinrvtires.com/reference-materials/load-and-inflation-tables/#/

Thanks,

Al

That's not necessarily true. Inflate tires to the mfgrs. tire placard in the vehicle, they built the vehicle and know the safe air pressure to support the anticipated weight.

[Darryl&Rita]

Grassy, you'll not find any tire manufacturer that will recommend less air pressure than what the vehicle mfgr. recommends.

That's not necessarily true. Inflate tires to the mfgrs. tire placard in the vehicle, they built the vehicle and know the safe air pressure to support the anticipated weight.

 

This is often repeated online wisdom. The placard goes out the window when a vehicle is modified. Even changing tire sizes, or load ranges, invalidates the manufacturers placard.

[Grassy]

This is where I get nervous. My truck is modified and I am running with different sized tires that what came off of it..

 

My weights are as follows..included in the numbers is the pin weight ..

 

Front axle - 6K
Rear axle (dually) - 10K

 

According to the Michelin chart http://www.michelintruck.com/en_CA/reference-materials/manuals-bulletins-and-warranties/load-and-inflation-tables/#/ I should be running less that 70 psi per tire if I am reading this correctly. I did that with the goodyears and was very uncomfortable.

 

I assume I am doing this wrong..

 

I am heading off on a 6K run this week... should I go down to 80 psi ?

 

Thanks as always..

[Darryl&Rita]

I'm aware of the issues you face, with a modified vehicle, Grassy, as I also face it with every vehicle I've owned.

This is my opinion only, and is worth exactly what you are paying for it. Your tires will tell you when they are inflated properly, if you know how to listen to them.

1. On clean, hard surface, with cold tires, use a piece of sidewalk chalk and make a line across the face of the tire tread, from shoulder to shoulder.

2. Continue this line up onto the outside shoulder, as a reference indicator.

3. Drive in a straight line for 100' or so.

4. Examine the chalk line. More wear on the shoulder indicates pressure too low, while center skuffing shows too high.

 

This method is highly non-technical, but will accommodate any tire on any vehicle, including trailers.

[Grassy]

Darryl,

 

Old school. I love it. Getting dark now so I shall try tomorrow.

 

Thank you.

 

grassy

[TireHobby]

If a vehicle is fitted with tires as directed in FMVSS the certification label/tire placard always has the correct pressures for the OE tires. Those pressures are good up to and including total GVWR for motor homes and total GAWR for RV trailers. If not the vehicle owner's manual will have recommendations for other circumstances.

 

Changing tires does not alter a vehicle. The new tires must provide - at a minimum - the same load capacity via tire inflation as the OE tires did. That's when a load inflation chart is necessary. It will provide the information necessary to get the load capacity of the tire up to par with the OE tires.

[Grassy]

I drive a modified vehicle... it came with 110 psi in all tires,

 

I have difficulty believing that ...with the wights that I have posted.. that 110 psi is what I should have in each tire..

 

theory / reality thing again..

[TireHobby]

I drive a modified vehicle... it came with 110 psi in all tires,

 

I have difficulty believing that ...with the wights that I have posted.. that 110 psi is what I should have in each tire..

 

theory / reality thing again..

Are the tires the original equipment tires?

[Grassy]

Tirehobby,

 

I have no idea. I bought the truck used with Goodyears ..and he hadn't changed them..however, the size of the tire was OEM..if you can call it that. As I understand it, Freightliner ships a bare chassis to SC who then mods it.

 

The PO ran 110 as per specs in all tires that I know...mind you, he was pulling a trailer that was almost double the weight of mine. According to the Goodyear pressure guide which is basically the same as Michelins, I should be 70 psi ish. I did about 6K miles on the truck with 110 psi... which was less than ideal.

 

I cannot believe that one size (pressure) fits all...and I am having trouble trying to decide who is correct..the inflation manual or retailers that have been selling and dealing with large trucks for years..

 

A conundrum for sure...