(I did a search about "tires" on this forum and there were 270 pages that came up so I thought it best to just ask my question directly)I just read a post on this forum from someone who had a rough ride in their Class C.We also have a Class C and at times the ride is rough. We have inflatable shocks. WE set them at 50-60 pounds.Someone posted an answer to the original poster stating that maybe his tires were inflated too much.I told my husband about this and he said he inflates our tires to 80 pounds. We have Michelin tires and they recommend 85. He likes to follow the manufacturers recommendations.So our question is: If we go lower will we do any damage to our tires?

Get your rig weighed, and go by the tire cos recommendation. 80 sounds about right for a C.

GizmosMom wrote:So our question is: If we go lower will we do any damage to our tires?Yes, there are 280 tire discussion pages....it's always been an 'interesting' discussion here on the Forum...If you lower the air pressure, you are also lowering the capacity of your tires to carry the weight of your rig (payload). The lower you air them the more they will heat up. Heat is the tire killer. Too low and yes you can certainly damage your tires...Some weigh their rigs trip read and loaded and air their tires accordingly. I keep it simple and air mine to the maximum as stamped on the sidewall....thus I get the maximum carrying capacity for my tires...confused now????

You should inflate your tire to the recomended pressure for your loaded weight, this is best done with 4 corner weighing, though if that is not available many people use axle weights from CAT scales at truck stops (the charge to get a CAT scale weight is about $10), also many agricultural fertilizer, landscaping, etc. places will let you weigh for free, or nearly free if for non-commercial use. Here is the Michelin inflation chart http://www.rvtirepressure.com/assets/images/extrapages/michelin_rv_load_inflation.pdfhttp://www.rvtirepressure.com/assets/images/extrapages/michelin_rv_load_inflation.pdfp.s. I disagree with the above advice, often the maximum sidewall pressure will result in a tire wearing abnormally as it is much higher not only than the actual pressure needed for the load, but also often well above the GAWR (Gross Axle Weight Rating) for the RV. For example my coach has a 6,000 pound GAWR for the front axle, and loaded down my coach is close to the GAWR therefore based on the chart I linked above I keep them at 80 psi which is 5 psi (safety margin)over the minimum for a 6,000 pound load for my size tires. If I were to run max pressure of 95 psi, this would give me nearly 7,300 pounds of carrying capacity, which is well over my 6,000 pound axle rating, but it would also cause a harsh ride, and the middle of the tires would wear out faster than the edges.

Ideally what Isaac-1 posted above is correct....but way too much hassle and realistically not possible on a day to day basis....thus...again, keep it simple and air them to the max and get on down the road.

Exactly what is the tire size? What does the door sticker say?Air shocks? I think you would do better with air bags or helper springs or a new spring pack if the suspension seems to be sagging.

Tire Inflation Questions | Good Sam Community

26 Replies

Mich_F
Explorer
Jul 15, 2018
Unless you have something other the stock tire size that came on your motorhome, I doubt that Michelin recommends 85 psi for tires that have a maximum 80 psi for maximum load rating stamped on the sidewalls.
Your vehicle should have a sticker on the door or door post where the MH manufacturer recommended front and rear tire pressures, which are probably 75# for the front tires and 80# for the rear tires, based on the vehicle being loaded to the front and rear axle max load ratings.
Grit_dog
Navigator
Jul 15, 2018
Some of these responses are like the guy (another thread about tire pressure......go figure) a couple days ago who said that as temperature increases, he also increases his cold psi. And the tires supposedly had more than enough air for the load to begin with.

Some folks level of understanding should not allow them to pilot large trucks and trailers.
Grit_dog
Navigator
Jul 15, 2018
Optimistic Paranoid wrote:
aftermath wrote:
Grit Dog said: "Grossly over inflated ties ( for the load, even if within max sidewall psi) can be almost as dangerous as under inflated tires in some (maybe different) situations."

I don't agree with this. Inflating a tire beyond what is needed to meet weight carrying needs is not a dangerous thing to do. It will most likely cause the tire to wear faster, but that is it. When the manufacturer prints the maximum carrying capacity of a tire at the maximum pressure listed it means that the tire is safe for this weight and pressure. If you have less weight than the max but you still air it up to max you are not doing anything dangerous.

When a tire is properly inflated, it's tread is making maximum contact with the road surface.

When a tire is overinflated, only the center of the tread is making contact with the road. Less square inches of contact means less traction. Less traction means longer stopping distance when you brake. It also means that steering will be less than optimal even on dry roads, and much, much worse on wet ones.

I'd call that dangerous.

You're right. Aftermath mustn't drive in rain or snow or ever need to make a panic stop or accelerate hard from a stop. Over inflated tires lose a large % of their available traction......but hey they match the door sticker....lol.
Grit_dog
Navigator
Jul 15, 2018
jplante4 wrote:
Grit dog wrote:
This may be good info for a little car tire with max 32psi or whatever rating, but it is NOT a 1 size fits all is correct recommendation. Period. Grossly over inflated ties ( for the load, even if within max sidewall psi) can be almost as dangerous as under inflated tires in some (maybe different) situations.

Also remember that car tires are over inflated by default to up the gas mileage to meet CAFE requirements. The door sticker amounts to government propaganda and should be viewed with that in mind.

Hard part is explaining that to the door sticker readers that believe if a mfg put it there, it is gospel. Same folks afraid of penalty by law if they remove the tag from their bedroom pillows!
Cummins12V98
Explorer III
Jul 15, 2018
"I told my husband about this and he said he inflates our tires to 80 pounds. We have Michelin tires and they recommend 85"

I would look at the sidewall of the tires. I am willing to bet they say 80psi "MAX". If so ask your husband why he is over inflating the tires.
jplante4
Explorer II
Jul 15, 2018
Grit dog wrote:
This may be good info for a little car tire with max 32psi or whatever rating, but it is NOT a 1 size fits all is correct recommendation. Period. Grossly over inflated ties ( for the load, even if within max sidewall psi) can be almost as dangerous as under inflated tires in some (maybe different) situations.

Also remember that car tires are over inflated by default to up the gas mileage to meet CAFE requirements. The door sticker amounts to government propaganda and should be viewed with that in mind.
Slownsy
Explorer
Jul 15, 2018
No but I believe that is why most advice to go over by 5lb to compensate for any side weight difference.
Frank.
Optimistic_Para
Explorer
Jul 14, 2018
wa8yxm wrote:

One a SCALE. one capable of weighing JUST that wheel. not it's mate across the RV or Tow Vehicle.

Speaking of that, does anyone know if the CAT scale people will let you drive just one side of your rig across the scales, and then get a second weight with the other side? Anyone tried that?
wa8yxm
Explorer III
Jul 14, 2018
OPtimistic said it.. Proper inflation = Full tread engagment = Maximum control = Longest tire life

To find proper tire inflation you need two things

One a SCALE. one capable of weighing JUST that wheel. not it's mate across the RV or Tow Vehicle.

Two. A chart in your case from Mitchlin.

I like to add 5 PSI to what M says .
Optimistic_Para
Explorer
Jul 14, 2018
aftermath wrote:
Grit Dog said: "Grossly over inflated ties ( for the load, even if within max sidewall psi) can be almost as dangerous as under inflated tires in some (maybe different) situations."

I don't agree with this. Inflating a tire beyond what is needed to meet weight carrying needs is not a dangerous thing to do. It will most likely cause the tire to wear faster, but that is it. When the manufacturer prints the maximum carrying capacity of a tire at the maximum pressure listed it means that the tire is safe for this weight and pressure. If you have less weight than the max but you still air it up to max you are not doing anything dangerous.

When a tire is properly inflated, it's tread is making maximum contact with the road surface.

When a tire is overinflated, only the center of the tread is making contact with the road. Less square inches of contact means less traction. Less traction means longer stopping distance when you brake. It also means that steering will be less than optimal even on dry roads, and much, much worse on wet ones.

I'd call that dangerous.