putting trailers & vans on blocks WHY

Hi Gerhardp1,
My immediate thoughts on the delivery pressure is they are carefully calculated to reduce the rolling resistance such that 102.397ml of fuel will get the vehicle onto the ship then off again.
Once it's off the ship, problem belong someone else,
Geoff.

From what factual base do you make that comment?
Here are some of many quotes from the tyre industry :

"When moisture gets into the tire, the steel belt package rusts and the tire's structural integrity goes. Goodyear helps reduce this with its Enhanced Casing Design (ECD) which is included in all of the company's mixed service radial tires."

"Keeping moisture out of tires greatly reduces the chance of tread separation, belt failure, corrosion around the valve stems, and other common causes of blowouts."

"Water can permeate a tire through any slight cut or nick in the tire surface. Once the water reaches the steel belt, oxidation occurs. The rust weakens the belt and can cause the tire to disintegrate during normal road operation. A visual inspection of a tire with a rusted belt may reveal slight tread wear, and the tire may appear to be in good condition. Thus, the potential for catastrophic tire failure can lurk below the surface where it cannot be seen."

"With steel belt tires now standard equipment, we sometimes see the outside steel belt separating. This is due to the oxygen and moisture leaking through the tire. A tire loses between 2% and 5% of air per month. This rusts the steel belts after a period of time. Aircraft and some truck fleets inflate tires with nitrogen to help stop this problem. "

"That's important because moisture could cause corrosion that could hamper the adhesion to the rubber at the weakest point of the tire and the very place where most of the tire failures occur, said experts who testified for plaintiffs and Firestone. "

There hundreds if not thousands - check for yourself.
No - it is not april. That part was factual.

Quote 1 is nothing more than advertising
Quote2 refers to keeping moisture out of tyres. When you consider a tyre is filled with air which can have 90% himidity I think they are advertising nitrogen filled tyres
Quote3 talks of water entering through nicks and cuts - this is alot more likely to happen driving through a puddle than parked in the garage
Quote4 refers to o2 and moisture permeating through the tyre - this must mean from inside out as it is immpossible for either substance to pass from lower pressure to higher
Quote5 was from highly paid "expert" witnesses who would hav had the defence tearing them to shreads in the cross examination

Prezactly,

Hi . Thats what I was told take the weight off the bearings. Which always did when getting home from a trip. Brian

Do you mean the trailer bearings don't get heated as often?
I can't see why they wouldn't get heated as much.

The vehicle brakes are used every day, and the brakes heat up the hubs. The trailer gets used intermittently, and depending on brakes, may or may not get heated up.