Awhile back, I had my RV weighed on a Cat Scale. It was completely empty of cargo and household items. It included a full tank of gas and propane, 1/2 fresh water and my wife and I. Results: 10,480 lbs front axle and 17,280 rear axle. Note that 10,40 is the front limit and 17,500 is the rear limit.
Then I had it weighed with full water, gas and propane, two passengers, full cargo (maybe 95%), tow bar and toad. Results: 11,120 lbs front axle, 18,200 rear axle, 3,700 lbs toad and 33,020 lbs overall.
I also initially had the 55 tires and running 110 psi which I did not like. After changing to 75 tires and beefing up the front axle to a 12,000 lb rating. I am more comfortable. Yes I am over on the rear axle but I agree with Boo (see post #19), that the rear is actually okay to 19,000 lbs.
Even though I have made it up 10% grades, I would not be comfortable without the beefier tires and front axle. The 340 is very marginal in weight carrying, so my advice - GET IT WEIGHED!
Gale & Hank- 2012 Berkshire 390BH