Air pressure in tires and GVW

[ezgoin]

I've seen several posts that refer to adjusting air pressure in the tires based on vehicle weight. How does this work? Is it the heavier the rig the higher the pressure should be? If my rig weighs less than max GVW how much should the air be adjusted?

[ezgoin]

wa8yxm wrote:

Many others feel you inflate all tires on the same axle to the HIGHEST pressure indicated for that axle.

I checked Goodyear's web site and this was their suggestion. Inflate per axle, not per side.

They also mention the possible problem with adjusting inflation based on weight, as your weights may change trip to trip. Their suggestion is to use max inflation based on GVWR. They also say adjusting PSI does not make that much difference in ride quality.

[wa8yxm]

ezgoin wrote:
I've seen several posts that refer to adjusting air pressure in the tires based on vehicle weight. How does this work? Is it the heavier the rig the higher the pressure should be? If my rig weighs less than max GVW how much should the air be adjusted?

You have the concept correct...

The tire makers have a chart that shows the proper pressure based on the load the tire is holding up and weather or not it has a partner (Single or dual).

You get the coach weighed You need the weight on EACH corner. There are a couple of ways to do this. One of the easiest is to go to http://www.rvsafety.com and follow the links from there. For around 40 bucks they come to you, they have the proper charts in hand, they find a level spot and you pull onto their portable scales (Same ones "Diesel Smokeys" carry. (Or you could just buy a round for the local Weighmasters).

Or you can go to a FLAT segmented scale (not a bridge scale like CAT scales) and pull on to the scale, get your axle weights and pull on again, this time only one side. Get the half axle weights.

Full less half = other half.

In which case you'll need to downlod the inflation chart yourself.

There is some discussion no what to do next.

I feel you inflate EACH corner as per the weight/inflation chart for that corner.

Many others feel you inflate all tires on the same axle to the HIGHEST pressure indicated for that axle.

(or you can just balance the load and then both methods work the same).

IN either case.. That's how to do it.

[rgatijnet1]

Load the vehicle with everything you plan to travel with and then add full fuel and as much water in your fresh water tank as you feel you should need. Personally I travel with a full water tank.
Then get your coach weighed just to see if you have exceeded your axle weights for the front or the rear.
If you have not exceeded the axle weights, then inflate all of your tires to the maximum axle weight and you will be good to go whether you have a full tank of fuel or an empty tank, out of groceries or you just loaded up at Walmart, Summer wardrobe or Winter coats.
Getting the coach weighed and inflating to that weight is a certain way to insure that your tires will be overloaded in the future because the weight changes and shifts as you travel. You just need to weigh the coach to make sure that you are NOT overloaded on the axles.

[wolfe10]

darsben wrote:
or just make sure you are under the weight limit and fill to the pressure on the sidewall and think about more pleasant stuff.

Yup, this works very well if your chassis maker left you very close to the carrying capacity of the tires (i.e. very little safety reserve).

But, if you have actual weights are well under their carrying capacity, your PSI could be well above the minimum recommended by your tire manufacturer.

So, there is really no "we know this will be what the tire manufacturer recommends" unless you weight your coach's axles and much better the individual wheel positions.

[Dale_Traveling]

From a general stand point the higher pressure, higher load carrying capacity of the tire. For best wear of the tire and ride comfort setting pressure to the load is your best option. If you don't know your coach weight setting pressure to maximum axle capacity is your next option. Your coach should have a placard with recommended tire size and load range along with listing the recommended pressures which will be based on the axle capacity.

With my coach I have a greater weight capacity in my tires than my axles. Also after getting my coach weight checked my normal weight is off the bottom of the inflation charts. As such using the charts doesn't work very well so I inflate to the maximum of my axles.

[darsben]

or just make sure you are under the weight limit and fill to the pressure on the sidewall and think about more pleasant stuff.

[wny_pat1]

RV Tech Library - How to Weigh Your RV

[GMandJM]

The manufacturer of your tires should have a load/inflation table on line. Here's a link to the the Michelin one: chart