Appreciate any advice for airing down 19.5" tires as on my F450 for driving on the beach.
As I understand these tires cannot be aired down as much as 16" or 17" tires.

Any advice or links to more info welcome.

 

I don't think you can do much. The tire inflation tables from the manufacturer stop at 70 PSI. I don't think the sidewall construction of the commercial tires is compatible with low pressure, even on the sand.

 

Not even remotely an expert here, but I would be making sure the sidewalls on the duals can't make contact when aired down.

 

In other words, driving a 450 on the beach would be a *bad idea*. It just isn't made for that. Look at the trucks the beach Rangers are driving, they all have wide, low-pressure tires...exactly the opposite of a 450. And, they don't weigh nearly as much. Even driving a 250 on the beach would not be a great plan, considering its weight and the fact that 10-ply tires are not designed to be run at 15-20psi. Half tons, Jeep Wranglers, and Toyota Tacomas are really the ideal type of beach running vehicles.

 

I've been deflating and driving on the beach for years. I currently have a '17 F250, had previous F350's and I regularly deflate to 20 psl for beach driving and towing my 12,000 pound toyhauler. I have and had 20" tires on these trucks. Zero issues with the tires.
if you're interested I can point you to the automatic deflaters I use as well as the onboard air compressor I have.

 

You are wasting your time, even if you did air down the tires they have such a stiff sidewall it won't make a difference.

Don't mess with them, turn off advance Trac a d lots of throttle, hope for the best.

 

Unfortunately, the 19.5 tires can’t handle the 20psi (max) needed to drive on the beach. The sidewalks aren’t designed to flex like that, and you’ll actually damage the tire by flexing it like that.
Our favorite camping spot was Assateague beach in MD. We’d take a 4K truck camper on my 350 at over 13k gvw and air down and camp on the sand. I had 37x13.5 tires on that truck. Aired down to 15-20 psi and it would drive through any sand or rut. We were running late on one trip and I said “13.5s are wide, I’ll just try it at street pressure”. No way. Made it 50 feet before I was buried (with lockers from and rear and 4.56 gears). Air down to 20, and it dug itself right out.
Saw plenty of stock truck tires out there that ran just fine. It’s not about the tire width, as there were truck campers with 245s that did just fine when aired down. The 19.5 wheels was my only hesitation about buying my 450. The benefits outweighed the loss of the beach camping.
Regarding duals touching, it is rapidly bad to do it at speed under load. If traveling slow for short distances, it’s just rubber touching rubber. A 350DRW (17” wheels) could air down and travel without worry onto a beach even though the rear tires may touch. Just don’t run a Dakar stage like that and you’ll be fine.

 

Any vehicle can drive on wet compact sand. Come to my neck of the woods for a real challenge. All beach, no water. And all loose.

Rules: 1) Don't stop on loose sand. Momentum is your friend. 2) Always enter uphill on loose sand...seen a lot of people stuck in a bowl. Gravity is also your friend.



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