Community Forums

ColoradoBnd · 05-31-2018, 05:07 AM

We are moving across the United States for our FIRST trip in our 06 Mountain Aire. Don’t think that’s a great idea for a first trip, but that’s what’s gonna happen. LOL. I do not have access to a four corner scale. I do have access to a cat scale. I downloaded the Michelin tire pressure guide. From what I remember here, I take the axle weight and use the Michelin guide? I seem to remember someone saying to add 5 psi to compensate for the lack of a 4 corner scale?

jenandjon · 05-31-2018, 05:46 AM

Read the side of the tire. It will tell you how much air to put in. No more. No less.

twinboat · 05-31-2018, 06:26 AM

There is no reason to fill the tires to what is printed on the side of the tire. That psi is for a maximum loaded tire.

The MH will have a tire sticker somewhere in it, near the drivers seat, with suggested pressures. Without weighting the MH, that would be a safe usable psi.

Then, there is the weighting front to back, math problems, adding some for off balance loading, if you find a scale for that, that will get you a pressure that you could use. Then add some? psi for insurance or adding stuff like extra water or people.

I go by the DOT sticker inside.

Crasher · 05-31-2018, 08:00 AM

Quote:

Originally Posted by jenandjon

Read the side of the tire. It will tell you how much air to put in. No more. No less.

Doing this will give you a rough ride with several tires over inflated for the load they will carry. Use the load inflation chart from Michelin and do as Twinboat said. When you get axle weights, if you still are uncertain, come back here with the numbers for help getting it right.

Ivylog · 05-31-2018, 08:38 AM

I love it when a trailer owner posts in the class A section what you should do for a trailer that rarely has more tire than needed. I use 70 psi in my tag axle tires but the sidewall says 130.
OP, axle weights +5 is what I’d do and my educated guess is 115 front, 85 drive, and tag 75.

Mr_D · 05-31-2018, 08:51 AM

Without weighing the rig rhe safest is to run what the Federal Weight sticker shows. That pressure is for the rig at it's maximum weight. The pressure may well be too high for the actual weight, but it is the safest till four "corner" weights can be obtained.

wingnuts · 05-31-2018, 08:56 AM

Quote:

Originally Posted by jenandjon

Read the side of the tire. It will tell you how much air to put in. No more. No less.

Sorry but the side of the tire only shows max air pressure. Normally could be up to 30 lbs less....that's why weighing your coach is so important. .

jenandjon · 05-31-2018, 09:26 AM

Quote:

Originally Posted by Ivylog

I love it when a trailer owner posts in the class A section what you should do for a trailer that rarely has more tire than needed. I use 70 psi in my tag axle tires but the sidewall says 130.
OP, axle weights +5 is what I’d do and my educated guess is 115 front, 85 drive, and tag 75.

Hey guess what. I also have a motor home. Why do you have to be such a snot?

Bobchambe · 05-31-2018, 09:27 AM

Be cautious of the tag inside your coach!

When I first bought my coach, I looked at the recommended tire pressure for my size tires and it said 65 pounds. Being new to RVing, I didn't know any better. After blowing two tires due to sidewall failure, I decided to rethink the pressure issue.

My side wall says "Max. Pressure 110lbs", I inflate them all to 100lbs.
Seems to work ok.

wildtoad · 05-31-2018, 10:00 AM

Quote:

Originally Posted by Mr_D

Without weighing the rig rhe safest is to run what the Federal Weight sticker shows. That pressure is for the rig at it's maximum weight. The pressure may well be too high for the actual weight, but it is the safest till four "corner" weights can be obtained.

Do this ^^^.

Using the pressure shown on the side of the tire should only be used as a last resort, NOT the first. That number is the minimum pressure needed to support the maximum weight the tire is designed to support. Use the placard in the MH as your default pressures until you have better information about your weights. This information is usually based on the GAWR’s for your chassis as defined by the manufacturer, but not always.

I for one have pressures (same) from both Ford and Newmar that are higher than what the Goodyear charts show for my units GAWR’s. Both numbers are significantly less that what’s on the tire (110). I’d never run the MH with 110 psi.

beenthere · 05-31-2018, 03:47 PM

ok again iil post the scientific method for weight vs psi.
if your tire says 120psi max and load rating is 7500 #'s and you weighrd your vehicles front{or rear} for example and it was 12800#'s then each tire has to carry 6400#'s.
so 7500 divided by 120 is 62.5pounds per PSI of carried weight..
so you have 6400 pounds of weight and then 6400 divided by 62.5 is 102PSI IN TIRE FOR THAT WEIGHT.. and I have checked lots of manufacturers recommended ratings sites and have not found one yet that will tell you its under inflated.. so why get all stressed out and wonder what to do?????
of course i did say have to weigh to find weight OF FRONT OR REAR carries... other wise maybe run recommended till you weigh....

now whats wrong with this method??? well nothing.. and i am just saying what papa taught me..

ThePowells · 05-31-2018, 05:06 PM

Four Corner Weigh on a CAT Scale.

1) Download the app and establish an account. When you are prompted for a unit or trailer number, just make up one.

2) Weigh the coach with the right side wheels off of the plates and steer / drive on different plates and download the scale ticket. CAT platforms are wide enough to do this. You don't have to be "centered", just as long as the wheels are not on the plate.

3) Circle around and do a re-weigh with the left side wheels off of the plate and download the scale ticket.

4) Go to the fuel desk and get the scale tickets and these will have the corner weights. Add the two fronts together and you have total steer axle, same with the rear.

Bear in mind that CAT weighs in 20 lb increments, so adding everything together may not agree with itself.

astrnmrtom · 05-31-2018, 06:19 PM

I was in a similar situation, the local CAT scale had steel posts on either side of the scale so weighing each side in two passes wouldn't work so I ran the pressure on the factory data plate near the driver's seat which was 115lbs. Then one day on our trip, we passed a small unmanned scale and I noticed it didn't have posts on either side. We took the next exit, circled back and did a four wheel weigh. Used the manufacturer's online pressure calculator and discovered I was good at 90lbs front, and 95lbs rear. I'm running them at 5lbs over that, and the ride has been so much smoother. I use a TPMS and pressures and temperatures always stay very reasonable, which tells me the tires are happy. Wear is even too, so the charts work. Don't worry too much. If you run what's on the tire plaque, you'll be fine as I'm sure the manufacturer plays it safe. I suspect the pressure listed on the plaque is for maximum Gross vehicle weight. A little too much pressure only makes for a harsh ride and maybe a little more wander.

ga traveler · 05-31-2018, 06:20 PM

If you were raised on a farm and miss the old buckboard, then for sure fill to max sidewall pressure. You will feel like you are jarring along the dirt road in the ole buckboard again. If you are not overloaded, the sticker by the drivers seat will give you the right pressure. My sidewall says 110 psi my fleetwood sticker says 80 psi. i run 85 to give it a tiny edge. At 110 the ride would be MUCH MUCH rougher.