Parking Camper On New Driveway Question

Oregun wrote:

HMS Beagle wrote:

Reality Check wrote:

I have to ask; what does air pressure in a tire have to do with ground pressure? What am I missing there? My truck tires go from 32 to 110, but the load on the ground doesn't change unless the footprint does.

Since the load on the ground is the same, the footprint has to change. If you ignore the stiffness of the tire carcass (which can be considerable), then the PSI in the tire = the PSI on the ground.

This is the very reason you air down the tires for sand.

Having trouble with what you are saying.
If what you are saying is true then removing the camper from the truck would not change the psi on the ground since the psi in the tire did not change.
And for a fully inflated tire the footprint barely changes when you take the camper off.
But taking the camper off should lower the psi on the ground 50 percent or more.

I'm sorry, but I'm having a hard time wrapping my head around this entire concept. Regardless of what the tire pressure is, if the entire weight of the vehicle is 100 pounds, and there are 4 tires, no matter how inflated the tires are, there is going to be 25 pounds pushing toward the ground on each tire (all things being equal).

What does tire pressure have to do with that.

Airing down tires on sand creates more traction, softer tire, bigger foot print as the rubber squishes outward and flattens under the weight of the vehicle. But the weight on those tires touching the ground is the same.

If this is so, then simply airing down your tires on a CAT scale would make the vehicle weights less (or more... however this theory works).

Regardless of pressure in your tires, a 10,000 pound vehicle is going to have 2,500 pounds on each tire (all things being equal). You can't change that. All you can do is spread that weight out over a larger area that touches the ground. That's what the lumber does.

To get back to the OP's original question, yes ... use lumber on the new asphalt. There again, the bigger footprint, the better.

I have a dimple in my new asphalt already, where the car sat. One tire left a dimple. Temperatures hit almost 90 and the asphalt was HOT. Gonna wait for another really hot day and see if I can push it more flat again.

There again, the reason for lumber under the tires is to prevent this type of dimpling. When asphalt is hot from the Summer heat, it gets soft. A heavy load will leave depressions. In a campground you don't notice it simply because it's not YOURS asphalt. But in your own driveway, you notice it!

OP, do all you can to protect the new asphalt. Lumber is so cheap and it provides a LOT of protection to the asphalt. Especially for something that is going to sit for a while not moving. Once it ages, it may firm up, but for now ... use the lumber.

HMS Beagle wrote:

Reality Check wrote:

I have to ask; what does air pressure in a tire have to do with ground pressure? What am I missing there? My truck tires go from 32 to 110, but the load on the ground doesn't change unless the footprint does.

Since the load on the ground is the same, the footprint has to change. If you ignore the stiffness of the tire carcass (which can be considerable), then the PSI in the tire = the PSI on the ground.

This is the very reason you air down the tires for sand.

Having trouble with what you are saying.
If what you are saying is true then removing the camper from the truck would not change the psi on the ground since the psi in the tire did not change.
And for a fully inflated tire the footprint barely changes when you take the camper off.
But taking the camper off should lower the psi on the ground 50 percent or more.

Reality Check wrote:

I have to ask; what does air pressure in a tire have to do with ground pressure? What am I missing there? My truck tires go from 32 to 110, but the load on the ground doesn't change unless the footprint does.

Since the load on the ground is the same, the footprint has to change. If you ignore the stiffness of the tire carcass (which can be considerable), then the PSI in the tire = the PSI on the ground.

This is the very reason you air down the tires for sand.

valhalla360 wrote:

Reality Check wrote:


Virgin soil 22 psi
Asphalt 29 psi
Compact soil 43-51 psi
Compact gravel 58 psi

.

If your asphalt is only supporting 29psi, you need to get your money back as you got some faulty product.

Passenger car tires run at 35-40psi. My truck tires go up to 80psi.

Even if you have a real monster of a truck camper, a 2x6 or 2x8 block should be plenty to spread the load out.

PSI ratings for asphalt are all over the board; similar to concrete (not in number, as concrete is so very much higher, but in reference to variances). But I believe that it carries a very low rating for static loads due to the changes caused by temperature. Temporarily, it can carry a very high point load; long term, it cannot.

I have to ask; what does air pressure in a tire have to do with ground pressure? What am I missing there? My truck tires go from 32 to 110, but the load on the ground doesn't change unless the footprint does.

Reality Check wrote:


Virgin soil 22 psi
Asphalt 29 psi
Compact soil 43-51 psi
Compact gravel 58 psi

.

If your asphalt is only supporting 29psi, you need to get your money back as you got some faulty product.

Passenger car tires run at 35-40psi. My truck tires go up to 80psi.

Even if you have a real monster of a truck camper, a 2x6 or 2x8 block should be plenty to spread the load out.

drmopar wrote:
I would suggest, as a Licensed Contractor in California, to have 4'x4' 3/4"-1" plywood centered under the tires when parked, and 2'x2' 3/4" plywood on the jacks. Don't crank the jacks down with a lot of pressure while parked. What temps are you getting? The hotter, the more you need the plywood. Sometimes you can hose off the driveway to cool, then place the plywood.

Truck campers don't have tires and the jacks support the weight of the TC to lift it off the truck. No more, no less.

Always get a kick out of these discussions.. huge sheets plywood, trust me because "I'm...." . This is simple stuff folks. Comments about asphalt (curing) are mostly correct. Hence, you ever notice they open the roads back up that they've overlaid the same day...? The stuff is soft, for sure, but waiting for curing is for not.

Taken from an older thread:

RV's are actually very light, but common ground pressure ratings are not always as high as folks think. With that, a pad doesn't have to grow very much to make a huge difference.

Some simple figures to use for common ground pressures;

Virgin soil 22 psi
Asphalt 29 psi
Compact soil 43-51 psi
Compact gravel 58 psi

Your 4" pad offers 12.5" of bearing; a 5" pad offers 19.5". Dividing the load by 4 isn't very practical because the load is lighter in the rear; I'll use 2/3 for the heaviest, the front.

1650#'s per leg for the example:

4" stock pad exerts 132#'s psi
5" stock pad exerts 84#'s psi
Compact gravel, for a 5" pad, offers 1131# of support.

i.e. asphalt for the same 4" area offers 362#'s of support, 5" offers 565#'s of support.

Simple, common materials to spread the same load, would produce the following:

2x4-12" 40 psi (42)
2x6-12" 25 psi (66)
2x10-12" 15 psi (114)
2x12-14" 10 psi (161)

Soooo, a 2x6-12" long, offers 66 sq inches of surface. Placed on asphalt, if offers 1914#'s of support (29psi x 66). A 2x6-12" would be ample for our example on asphalt, but if you want to be further on the safe side, a 2x10-12" offers 3306#'s of support. It doesn't take a piece of plywood to do the job (which, frankly doesn't work unless you get into the 1 1/8", and then, only for small areas). Dimensional lumber is your best choice for inexpensive, easy to obtain, and consistent. When's the last time you saw dunnage under a crane made of 'plywood'? Correct, you haven't. It doesn't work.

Change the formula up for what you're comfortable with. Camper weight divided by what you consider the worst case scenario per leg (front legs usually carry more weight than rears), then that 'weight' divided by the size of pad.

Figures rounded; generalizations offered for the purpose of getting through life. Face it, this isn't life safety stuff.

Don't listen to the paver who reccomended you park it in the same exact spot and let it dimple the asphalt. That's the most ridiculous thing I've heard.

First, theoretically you should be able to park it just on the jacks and see no settlement. However, residential mixes are cheaper quality mix usually, some better than others and while asphalt compressive strength is higher than the pressure your jacks would place on it, over long periods of time, asphalt can creep or shove.

Simple solution , just use any sort of plywood or dimensional lumber blocks, 12" long treated 2x6 block would be cheap and ideal and last a long time and you'll see zero imprint or settlement.

HMS Beagle wrote:
A 3/4" piece of plywood is much floppier than a 3x8. I'd use a 3x8 about 12" long. If you put 1000 lbs in the middle of a piece of 3/4 ply, most of that pressure will end up right under the jack leg. It's better than nothing, but surely not better than a 3x8. A 3" piece of lumber is pretty stiff, and will spread the load somewhat evenly. Let's say 1000 lbs on a 3x3 jack foot is about 100 psi. Spread onto a 12" 3x8, that goes down to 40 PSI - about the same as a sedan tire.

I think Im gonna do just that, Thanks HMS Beagle and Thank You everybody ! Lou

Depends too on how thick the asphalt is. Here they do 2,3 or 4" thick.
Brian