How much air in the tires? Need advice... First "real haul"

Because I know my rig is over the GVWR, I make the choice to increase tire pressure above the door placard. This is for several reasosns.....

Although I am under GAWR, I also recognize that axle weghts are static and because I am over GVWR I know that I will be puttying more dynamic load on the axle than Dodge assumed when setting the pressure.

higher pressure reduces side wall flex. Makes for a more stable ride and with less asway, reduces dynamic loading.

I assume that it gives me slightly better fuel economy.

Sleepy recommends it after years of experience running his tire pressures at max. That alone is enough of a reason.

I run at 75 psi minimum and go to 80 if I am pulling anything.

It is a mistake to oversimplify and also think you have the best solution to a problem. Fwiw, there are reasons not to run the maximum bicycle pressure as well which include changing the stopping characteristics and handling of a bicycle. I'm pretty sure tires wouldn't list a maximum pressure if there was only "one" pressure to run. Ymmv. ;)

Lets get this back to basics...

Get out your bicycle...

Fill the tires to the maximum pressure on the side walls... pedel it around the neighborhood including over some rough patchs of road and up a steep hill.

Now drop the air pressure to the point where the sidewalls on the tires are squishy... it takes a lot more of your personal horsepower to peddle it even though it isn't so bone jarring in the rough road portions.

It's a little harder to control when the tires are squishy, the sidewalls bulging

Now, take a look at your truck with the camper loaded for your trip... are your sidewalls bulging?

If you have a duallys is there a danger that the tires will touch, building up heat? Is there a danger that rocks might get wedged in between the side by side tires?

Think about your bicycle... is your trucks engine and your mpg (energy) going to benifit from the maximum air pressure in your tires for 99% of the roads you'll be driving on?

As I've said before... I am happy with 80 PSI all around... and the 15 mpg, stable ride.

Hope you enjoy your trip.

Sleepy

My camper weighs in at just around 4,000lbs totally loaded and wet. I've used 80psi in my tires also for the entire time I've been TC with 16" tires. It feels more stable to me. I'm no expert about this at ALL, but I've tried it at 68-70 and it did feel a little "squishy" to me, but that's just my own truck, camper and tires. Your results may vary.. ;)

Dak

For the best fuel economy... run your tires at the highest presure on the sidewall... the ride might be a little harder than the squishy lower pressures

try it both ways...

I like the no sway, no wobble, and the higher mpg at 80 psi

I am running 75 psi in all 7 tires, 80 psi max stated on sidewalls. I have 2 rubber tire valve stems in front because the way the MKW rims were made, unable to use metal valve stems. The rest of the tires including the spare are metal valve stems. Make sure the metal valve stems are made in the USA. The Chinese metal valve stems are not tested. I have a heavy TC in bed of truck.
Ben

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Wayne
Moderator

CapriRacer wrote:
... towing within the limitations of the truck

The OP isn't towing anything, he's "hauling" a truck camper in the bed of the truck.

JPedro wrote:
Back to the question..... I keep my rear tires at the door sticker recommended 70psi, but within a half hour of driving with my overloaded TC the tire sensors show 80psi. Seems about right, but I wouldn't want to start out at 80 and go to 90. I'm wondering if folks with 19.5's see their pressure go from 110 to 120psi?

This pressure increase is normal. The tyre inflation/load tables specify that initial pressure must be done with cold (ie ambient temperature) tyres and the running pressure will be correct once the tyres warm up. My bigrig pressures go up by far more than 10psi, especially on a hot day and especially on the side facing the sun.

In some cases - because excessive tyre flex of underinflated tyres generates more heat which increases the hot running pressure, increasing the cold pressure to the correct value might actually result in a lower hot running pressure. This fact is used by some to determine what the correct pressure should be. Small sedan tyres - 4psi increase. Less means too hard, more means too soft. Larger 4x4 tyres - 6 psi increase and so on. Not an exact science but apparently works for some.

BTW Rated rim pressure may be a limiting factor when high load rated tyres are fitted in an effort to handle overloading.

Where do you haul thge air compressor... changing air pressures in your tires as you change roads... bull!

Comes from doing most of my driving in countries where there are still unpaved tracks to enjoy. For instance the Canning Stock Route in Australia - 2000km of washboard that killed 5 mercedes off-road vehicles with factory mechanics following them - because they ignored sensible advice to slow down and run lower pressures.
South America where you can be off paved roads for days at a time etc etc. Morocco the same. No Good Sam anywhere there either so you wreck it, you fix it.

Where do I haul it - A good 12v compressor will fit in a shoe box so just leave out a slab of beer and carry two 12v compressors like I do.

Actually I tend to go the other way in those sort of situations - run the lower pressures on the dirt and if there is only twenty or thirty miles of pavement, just drive slower on the pavement.

So no, I don't air up the tyres again every time there is a half mile stretch of pavement because that would be even sillier than NOT airing down when faced with a hundred miles of rough roads.

Of course all this theory is useless unless you go to the trouble of weighing each axle - and preferably each tyre group - separately and then check the tables.