You're both right (or wrong, depending on how you look at it). Both of you are giving true statements regarding the math, just arranging the equations different ways. Force (load) equals pressure times area, but area = force divided by pressure too. The math doesn't care which way you arrange the equation. (But you're both wrong saying that the other is wrong.)

 

anyhow i prefer a skinny studded tire on ice for the best traction.

 

I'm running 10 ply 235/85R16's on my F150. I keep the tires inflated as per the sticker on the door. When I'm loaded up to go hunting or camping I bump them up to 50ish, depending on how much weight I'm carrying. Once empty I drop the pressure down again.
I have a highway tread as I don't really go "off roading." Mostly just gravel or shale roads when hunting/camping. The rest is all pavement. I have about 15,000 K on them now and I'm happy with how they perform and how they are holding up.

 

Can you post some pictures please?

 

In the real world we call what you're talking about flat/overloaded tires that will quickly wear out, overheat, and/or blow. In the real world we have weight ratings and max/min pressures. Yeah what your saying has merit in the reverse if for example you put semi tires on a F150, then yeah you have a VERY small contact patch. Or has merit off roading where you are going slow and using tires designed to deform with very low pressure. But to just suggest that an overloaded or under pressure tire will just have a bigger contact patch and be fine is VERY dangerous to everyone on the road.


The math doesn't care, but the tire does, the way he's stating it is very dangerous logic for someone that may be inclined to cut corners and/or doesn't understand the risks.


All this aside except as mentioned by Jason, is why I in general am an advocate of leaning towards a taller and narrower tire. A tall narrow tire that can conform/flex without damage and handle rather high pressure is a very versatile tire. At higher pressures they have low rolling resistance, can handle heavy weight and penetrate water, snow, mud etc to get traction on the under surface. At lower pressures they make for a large long contact patch to float, conform very well to absorb surface shapes to both get traction and make for a smooth ride. I put my money where my mouth is, on my daily/everything truck(F350) I roll a 37/12.5 mud tire with a 65psi/3970lb max. If I could find a light truck tire(can conform) in a 37/10.5(or so) with a 80psi(or higher) max I'd roll that, but I can't. Everything "more" get's wider, or is a heavy duty(commercial truck) tire that can't conform or handle light weight well. There is a 39.5/13.5 65PSi/4080lb tire I might go with next time.

 

I'll take some today and try to post them. Photobucket and I didn't get along the last time I tried to post pictures. None of the three links provided for my pictures worked

 

Thank you much! You need to use the image code on photobucket

 

The sticker on your door is not meant to be used for any other tire size than what it says. 50 psi should be close to the unloaded minimum you should run on load range E tires. Running less than that places you at a higher risk of blowing out a sidewall. Even though you just have a half ton, you should be running about 45 psi minimum. 55 is the lowest I ever go on mine, and that is in the fall for hunting and driving in fields only.

 

Hang on a second...I think you misread what I wrote. Nowhere did I advocate for lower pressure in tires than what is recommended/safe/correct/etc. I was merely using some numbers that make things easy to calculate.

My only point was that contact size is not an easily measured quantity, but it is calculated fairly quickly from two quantities that are pretty easy to measure--tire pressure and load on each tire.

So, if you had two tires at 50 PSI and 1000 lbs on them, one a 235 width and one a 300 width, which will do better in rain and snow? it's not based on contact area, but the width of the tire--they both have the same contact area with the ground.

I tend to prefer higher-ply tires that can hold more pressure, thus allow for a smaller contact area, better mileage, longer wear, even though it does sacrifice some ride comfort.

Jason

 

I definitely agree not to use the recommendations on the door sticker when you've changed tires significantly (then again, after the Explorer / Firestone debacle I'm not sure I'd ever use the door sticker). But 45 - 55 psi minimum on load range E tires is too conservative. I've run LT235/85R-16E at 40 psi on the rear of an empty pickup and worn out the treads of about 6 sets of tires with no sidewall failures. I don't think I'm coming very close to a limit either since the sidewalls aren't running noticeably warmer than they do at higher pressures.

 

I have the pictures of my tires on Photobucket but I have no idea how to put them here. I can probably put one at a time but for more than that I don't know what to do. Frustrated since the so called "upgrade" on Photobucket.

I understand what is being said here about tire pressure, I just don't necessarily agree with it. I have used my truck in 38 (100) degree weather and have never had any tire become more than just slightly warm to the touch. I'm not concerned with sidewall flex generating too much heat with my truck empty. As mentioned earlier, when loaded I increase tire pressure.

 

OK, so here's a photo of the tread pattern I have on my truck. The tires are Kumho Road Venture 235/85R16 Load range E 10 ply. Max pressure 80 psi. I run 35 front and 41 rear when empty and about 50 or so when loaded.

 

I put those SAT KL61's on my wife's Honda Passport. (undercover Isuzu Rodeo)
245/70-R16 D-rated and running around 37psi.

They seemed a good tire for New England winters but she never went off road on purpose.

How do you like them on your truck Dave?

 

I like them a lot. They are quieter on the highway than my old 15 inch tires and they inspire confidence when I'm driving over some of the crushed shale used to cover the roads where I sometimes like to hunt (no flat tires since I started using them on, what can only be described as, little tiny shards of glass designed to look like pointy rocks )
Incidently they have the mountain and snowflake symbol on them so they are designed for extreme weather. They are great on dry pavement, in snow, rain and on gravel. Not so great on ice. Partly, I think, because my truck is too light to really press the tread into the surface for what little traction is available on ice. I run them all year and, even though they were expensive, I am very happy with them.

 

I bought them for the M+S rating too.
I'm glad you like them on your truck, and you find them tough enough for the road surface.

Interested in your comment about them being expensive.
The size and rating I bought were were only $242 a pair, delivered!
It didn't seem bad. (I do my own mount and balance at my friends garage)