Identify and correct tire pressure

The most accurate way is to weigh all four corners of your RV when it is fully loaded. Then go to your tire manufacturer web site and they will have a chart giving you the proper tire pressure based on the weight of your RV.

First load the coach then have it weighed. At a minimum you want the axle weights. Ideally you want the corner weights (weight on each tire). Next go to the website for the make/model of your tire and lookup the pressure rating for that weight.

There is no single "correct" pressure. With the types of tires used on a Class A it is weight dependent.

Worst case use the max axle loading and pump them up accordingly. The ride will be harsh but you will not be under-inflated for your load.

Get four corner weight. Then look on the tire mfgs web site, locate the tire model you have and read,the load chart. Adjuat the pressure for each corner according to the chart.
Alternative method. Inflate them to the maximum cold pressure as listed on the tires side wall and quit worrying about it.

Sidewall pressure is the maximum pressure the tire is rated for (some of the time this may be higher than the wheel is rated for). The pressure on the data plate inside is the RV manufacturers suggested pressure, though finding correct operating pressure requires weighing the coach as loaded for travel and adjusting tire pressure accordingly see. http://www.rvsafety.com/articles/written-articles/113-rv-tire-pressure for more information, there are other sources online google should help you find them.

Old fashion way: make chalk marks across all the tires. Drive down the road.

If the chalk wears off evenly across the tread you have the correct pressure.

If the chalk wears off in the center of the tread you are over inflated.

If it wears off on the edges you are under inflated.

You rig should have tire pressure recommendation plate - look around. Use that tire pressure until you can get the rig weighed. When you weigh make sure the rig has typical weight when traveling (fuel, water, and something that emulates the weight of the typical number of passengers). I used a truck stop to weight my rig - they had nominal charge and the weight machine only determined weight of front/rear axles which was acceptable to me. Michelin website has nice table which converts weight to tire pressure based on size of your tire.

Totally ignore the tire pressure stated on the tire as you will most likely never put that much air in it. First is to set the pressure to what the placard in the RV states. This assumes you have the OEM tires. Take it for a drive down country roads and some interstate and if you find the ride is fine, then leave it alone. If you find it harsher than what you want, get your mh weighed as mentioned above and use the tire charts which show the minimum pressure required to support the weight.

There seems to be some confusing information given here.
It’s important to get each corner weighed if possible. Then adjust your load if possible to even out your weight. You don’t want excessive weight on one side or the other.
Then use your tire manufacturer inflation chart to choose the correct pressure for your tires/load on each axle.
Your tire pressures should be the same on each side of an axle. Example. Front axle requires 75 psi, inflate both left and right side to 75 psi.
Different air pressures on your steer axle could cause your vehicle to pull to one side or the other.
If your weights are different on each side, you would inflate both sides to the heaviest load.
Hopefully I didn’t make it more confusing.

Ideally you want to know the four corner weights. That said, it's not convenient, not easy to locate someone/someplace to do that and just not practical. Alternatively just have each axle weighed and go from there. Most large truck stops, grain elevators, moving companies, even closed weigh stations if you're in Oregon or Washington have scales. Google's your friend - put in your zip and scales.

1. Load your rig as you would normally travel. Full fuel, 1/2 tank fresh water-less if that's normal for you, etc.
2. Go to the scale you've chosen. Pilot/Flying J charge $10.50 for weighing.
3. Pull up onto the scale making sure each axle is on a separate scale-they usually are broken into three scales. Front axle on one, rear axle on the second and the tag on the third.
4. Release your air brakes if so equipped.
5. Press the button and wait for the operator to tell you they have your weight.
6. Go inside and get your weigh slip.
7. Boot your computer and go HERE. Put in your tire size and that will tell you how much pressure should be in each tire. Remember, all tires on an axle should be set at the highest weight for that axle. In other words, you don't want 90# on one steer and 100# on the other.

As you can see, tire pressure is important and really pretty simple once you do it. Since we full time and our weight fluctuates as DW buys and gets rid of "stuff" we weigh our coach regularly. As we use Flying J for fueling, I will pull onto the scales about every fourth fill up or so and adjust my air pressure accordingly. YMMV....Dennis

For the OP - Something no one has mentioned - tire pressure should be set COLD, meaning not driven and without the tires affected by sun. Determine needed pressure as mentioned by most of the above posts by weight. If you don't have a compressor at home, air up to tire sidewall maximum and drive home. Next morning, before sun heats the tires up, lower pressure to what you calculated by weight. It is not uncommon for sun/driving to cause a 10# or more pressure increase.