Seneca tire pressure

[RoyB]

I have been monitoring the threads about tire pressures. I started with my dealer's recommended 110 psi (max) and thought I'd bought a tank. It bounced with every penny run over and wandered with the wind caused by semis. I have weighted my 40' MH by axle and gone to the charts and found that they recommend 80 front and rear. Since changing to 80 psi I have dropped my intention to add suspension items because the ride is not only smooth but the whole rig has become much more stable.

[bmeaney]

Kudos to CAG, he read the sticker on the driver’s door frame. Jayco lists 110 psi as the recommended tire pressure for my Seneca. So, I guess I have to decide, the manufacturer or the company whose tires have travelled millions of miles in trucks and RV’s.

[2manywheels]

We keep ours at 98 to 100 cold. Our first 5000 miles o.n our Seneca were at 100 cold, as that was what the previous owner recommended. I then did about 3000 miles at 93, and cant say that i felt much of a difference. I do feel like i noticed more wear on the outside treads, but have no measurements to back up that claim. We bumped it back up to 98 to 100 on all 4 corners last week and things feel fine. Have yet to find a place to weigh all corners to see how balanced we are, ut would like to.

[jadatis]

Originally Posted by jadatis

With my made spreadsheet , I come to Front 81 psi, Rear 73 psi. Then I calc with an extra safe formula, and furst add 10% reserve, and then still comfort and gripp are acceptable.
F 86 R 76 probably still acceptable gripp and comfort, for that I lowered the maxload for higher speed. SO 100 must be driving like an old army truck.

My calculated pressures are on the high side even, assuming you weighed fully loaded, also all the persons in it.

So If you think it still scarry, begin with F90 psi and R 80psi.

This is cold measured at 65/68 degr F. Cold is when in and outside tire temp is the same, that simple.
Warm when driving about 55mph , pressure will rise about 10%, when ambiënt temp is 65degrF. , and no other factors that highen up the temp in tire.
Within a sertain range of ambiënt temp, heating up of rubber of tire is in balance with cooling down, if you calculate the cold measured pressure back to 65/68 degr F, and you will come to the advice pressure.

When verry cold outside, for savety, you dont need to highen up the cold measured pressure, but may do so for road- handling.

But when verry hot outside, dont blead down to advice cold pressure, the tire then needs that higher pressure to give lesser deflection ,so lesser heatproduction, because cooling down is also worse, because of smaller temp differences, between rubber and in and outside air.
Not any part of tire may reach a sertain temp at wich the rubber hardens permanently, and crackes.
If this only happens once, mechanical forces tear the crackes further, untill mayby only after 3 years that far that tire blows or treath seperation.

[Tireman9]

Originally Posted by bmeaney

CAG, if I'm not mistaken, all tires have an indicated maximum recommended tire pressure imprinted on the tire. It does not mean the tire must be inflated to that pressure but only that it should not be inflated (cold) above that pressure. At noted elsewhere, Michelin has provided a series of detailed tire pressure charts for their truck tires that list the recommended tire pressures for each tire based on the axle weight, differentiating between single or dual axles.

I never received a recommendation from Jayco concerning a suggested tire pressure. The recommendation came from the salesman who sold us the unit. Basically I'm taking Michelin's recommended pressure at my axles weights and adding 20 psi. I doubt that could be considered "underinflated."

All that said, thanks for taking the time to reply.

All RV per DOT have "Certification label" that identifies the tire inflation recommended by the MFG and RVIA says that what is needed in the tires to support 110% of the GAWR. This does assume a perfect 50/50 side to side load split which is unrealistic based on actual scale data of thousands of RVs. By law it is the RV company not the tire mfg that is responsible for the information on the label. You, as the owner can ignore that information and set the inflation you want but to do so without understanding all the consiquences and not considering all the facts may end up paying the consiquences you do not expect or want.


Knowing about the real side to side load split is why individual tire position scale weights are recommended. It is also important to understand that tires do not always fail the first mile they are abused, damaged or underinflated. Damage is cumulative. It starts at the molecular level then grows to the microscopic and eventually can result is a belt separation many hundreds of miles later. Thres do not repair themselves simply because the excess load was removed or the underinflation was corrected or the driving speed was lowered.


I do wish that every RV owner would read THIS post and take the information to heart.

[bmeaney]

Thanks to Tireman9. You are certainly more knowledgeable about this issue than me! While not questioning your response I am curious why a manufacturer would recommend tire pressures so much higher than Michelin's specific recommendations for my specific tire. Wouldn't Michelin's engineers take into account all the technical factors you mentioned? Wouldn't tire manufacturers be just as liable for damages resulting from erroneous recommendations. Are there other factors involved besides weight? Thanks for your thoughts.

[Tireman9]

Originally Posted by bmeaney

Thanks to Tireman9. You are certainly more knowledgeable about this issue than me! While not questioning your response I am curious why a manufacturer would recommend tire pressures so much higher than Michelin's specific recommendations for my specific tire. Wouldn't Michelin's engineers take into account all the technical factors you mentioned? Wouldn't tire manufacturers be just as liable for damages resulting from erroneous recommendations. Are there other factors involved besides weight? Thanks for your thoughts.

I can walk you through the calculations and show how the inflation on the certification label is OK.


I need to know what the stated Tire size LR, Inflation and the F & R GAWR, as shown on your Certification label aka Tire placard.

[Tireman9]

Originally Posted by LaMigra

I just had my 2019 Seneca weighed at the FMCA Rally in Tucson. Based on my vehicle's weight; RT Front 3900, LT Front 4400 total: 8300, leaving me 1700 under the GAWR. RT Rear 8300, Left Rear 9150, total 17450, leaving 1550 under the GAWR.

The left side is 1350 over the right side. So I need to rearrange somethings. Based on the weight as noted above, Michelin recommended psi is 80 front and 85 in the rear.

Interesting that your original weights come out to be about 47/53 and not 50/50


In my blog and on many posts I have suggested people use 53% of the CAT scale reading for an axle when consulting the tire Load/Infl tables until they get the more accurate "4-corner scale readings.
Nice to see I would not have been too far off with my "rule of thumb".

[RVermont]

Originally Posted by Tireman9

I can walk you through the calculations and show how the inflation on the certification label is OK.


I need to know what the stated Tire size LR, Inflation and the F & R GAWR, as shown on your Certification label aka Tire placard.

Thanks for your valuable information on this subject.

Here is the information on my 2018 seneca.
Front axle. 10000 lbs. Jayco sticker says 110 psi
Raw dual axle 18000 lbs. Again 110 psi

Tires are Michelin 275/80r22.5 g Xze2 tires.

Attached is the Michelin pressure guide.

If I run at max weight and evenly balanced would the 95 psi amount be correct or am I missing something. Currently I am much lighter then allowed weight.

[Oma/opa]

That's how I read it. I currently run 85# all around based on actual axle weight (not 4 corner) + 10%

[bmeaney]

Originally Posted by Tireman9

I can walk you through the calculations and show how the inflation on the certification label is OK.


I need to know what the stated Tire size LR, Inflation and the F & R GAWR, as shown on your Certification label aka Tire placard.

Tireman9, I am attaching a image of my Seneca's two door stickers

for your analysis. You already have my info on tire model, axle weights and the Michelin chart.

[Tireman9]

Originally Posted by RVermont

Thanks for your valuable information on this subject.

Here is the information on my 2018 seneca.
Front axle. 10000 lbs. Jayco sticker says 110 psi
Raw dual axle 18000 lbs. Again 110 psi

Tires are Michelin 275/80r22.5 g Xze2 tires.

Attached is the Michelin pressure guide.

If I run at max weight and evenly balanced would the 95 psi amount be correct or am I missing something. Currently I am much lighter then allowed weight. Attachment 54403

OK here is how I would calculate info for the sticker


F GAWR 10,000# Per DOT 5,000 per tire Per RVIA 5,500 per tire min

Michelin 95 psi > 5510 (10# margin too low) so 100 psi min
110 psi gives 6,175# per tire capacity 22% Reserve Load



R Gawr 18,000# Per DOT 4,500 per tire Per RVIA 4,950# per tire min
or 9,900 per pair
Michelin 95 psi >10,140 (240# margin)
100 psi > 10,520# 110 psi > 11,350 45% Reserve load


Jayco might also want to give a single inflation number for all tires.


You as the owner can decide to lower the inflation BUT you should only do that once you know the ACTUAL load on the heavy end of each axle.


Note that some Class-A have been found with over 1,000# side to side unbalance. You might want to review my blog post on "Reserve Load".

[LaMigra]

Originally Posted by Tireman9

Interesting that your original weights come out to be about 47/53 and not 50/50


In my blog and on many posts I have suggested people use 53% of the CAT scale reading for an axle when consulting the tire Load/Infl tables until they get the more accurate "4-corner scale readings.
Nice to see I would not have been too far off with my "rule of thumb".

Two months before I went to the CAT scale, the front was 8560. Rear came in at 17840.