The eternal question, how much is too much. And as an added bonus a picture of Bobby Orr skiing a Ford Ranger.
Driving Under Pressure: Editorial & Features at Officer.com

 

good article! Thank you Buzz

 

I would run the max at 44 pound's, it truely helped my mpg.

 

Overfalated tires are dangerouse too. When you drive fast pressure increases and you can easily get 60. And usually not protector cracks, but side wall of tire. And tire becouse of overheating and overflating blows at high speed...

I advice you to inflate tires according vehicle specifications and get tires designed for much higher pressure then your manual say to have in tires.

I use C235/70R14 (not P), becouse cargo tires are designed for 4-5 bar pressure and 600-800 kg load.

 

It's not over inflated, it say's right on the side of the tire, max air presure, 44 pounds. I ran the bfg at ko's 265/75-16's, it's a very tough and sturdy tire with very strong side walls. The side walls are made to run under inflated on the trails for better traction. I think the russians love to argue ha ha.

 

Pablo's right about increasing temperature at speed though. It's Charles Law which in it's simplest form is as temperature increases pressure increases. Tires get hotter when driving on asphalt from friction and so on. Wendell your right also. Max pressure on the side wall is way under burst pressure for the tire and valves and such, assuming the tire is in decent shape. We are all enthusiasts on here so I assume all our tires are in good shape. Anyway, I run 35psi front and back.

 

I bumped mine from 32 to 42psi even though my tire is rated for 50psi. If my ride isn't too harsh then I will try 46psi, then up to it's max after that. A tire will get hotter due to the flexing of the sidewall, a major cause of failure from running under-inflated. After a 15mi trip mine were still cool and at the same temp as the outside temp was... 42*F. It was the same temp as when it started.
I'm trying to get 23mpg this week, with a goal of 25mpg which will get me close to 4banger specs.
In the hilly country where I live that is going to be tough to do, since for every downhill there is an uphill. I have been averaging 21.5mpg with my tires at 32psi. For a truck with over 180,xxxmi that isn't to shabby.

 

I am a big believer in safty, but I trust the manufactures posted max tire presure on the tire. At max you have less rolling resistance and inturn better mpg, yes it can stiffen up the ride, but at 4.00 a gallon, it's a good trade off. Mine have allways been 4x4's that ride rough anyways, whats a couple more bounces. I hear yesterday that oil could reach 200.00 dollars a barrel soon, thats 7.00 bucks a gallon. Heyllium in thr tires maybe next hee hee.

 

Howstuffworks "How Self-inflating Tires Work"

Read it first! Overflated tire does not wear regularry and hardly goes over bumps, more noise and overflated tire has worth handling. Inflate tires according vehicle specification.

 

I believe the Code3 mentioned in the article refers to high speed chases. If that is the case then he's saying that the cars actually handle better, not worse at the higher inflation. I've noticed no change in the handling or ride at 42psi so I'm going to increase the pressure up to 46psi this weekend. I can see where 4x4 offroading could be problematic due to changes in terrain and road composition, but I can always let air out and drop back to 30psi for the extra needed traction, and re-inflate them when I get home.

 

IF a tire states max psi of 45 that accounts for increase or decrease of pressure due to driving / temperature. If it didnt you would have to constantly change your tire pressure while driving to meet specs, which is absurd.

 

I bumped the pressure in all my 16" tires to 38psi today. Rides nice.

 

Mine are 235/70/R15 on a '99 Sport x-cab with 4 speed auto and a 3.0 liter. I always feel best at around 36 or a little over. Tires hold the road, it steers well and I believe I'm getting the best mileage which is more important now. A pickup should have a hard ride, not like your dad's Grand Marquis. Can't understand why I only get around 22 mpg highway though.

 

OK here's the deal.

P-series tires - example: P235/70R16 (Pablo, here in the US C-series are extremely, extremely rare) typically have a max cold pressure rating of 35 or 44PSI (depending on the tire). You can safely run up to that max level usually without any adverse effects, other than a harder ride.

LT-series tires - example: LT235/70R16 Load Range E, typically have a max cold pressure rating of 50PSI (For load range C), 65PSI (For load range D), and 80PSI (For load range E). Again you can safely go to the max pressure (assuming your rims and valve stems are also rated for it) with no adverse effects, other than an even HARDER ride.

LT tires have a LOWER weight rating than a P tire at the same pressure. So basically at 35PSI an LT tire may not be able to support the same amount of weight as it's equivalent P tire (but LT tires can handle higher pressures, allowing for more weight).

As a result, if you are 'upgrading' from a P to an LT, the general rule is to add 14PSI to the manufacturers recommended pressure (typically 30PSI on the Rangers) to compensate for this.. without exceeding the tires MAX pressure.

Here's my take on this... if you have a P series tire, put 35PSI in it (or the manufacturers recommended pressure, whichever is higher), regardless of what the tire sidewall says.

If you have an LT series tire, put 50PSI in it unless you are hauling or towing, in which case set it to it's MAX PSI level.

I've found that with P tires anything higher than 35PSI (even in tires rated up to 44PSI) has a negligible impact on fuel economy, and only results in a rougher ride and excessive wear in the center 50% of the tread.

With LT tires, anything more than 50PSI REALLY makes for a rough ride, again with very little to no improvement on fuel economy.

Now if you don't haul or tow, and want your car to ride the smoothest and don't mind a mild hit to your fuel economy, then set your tires to 30PSI (or the manufacturer's recommended pressure, whichever is higher).

 

Thanks for the imput, I'm running 31-10.5 15LT and they are rated for 50psi. So now I'm going up to 46psi. My target is still 25mpg.
Billj6, over 60mph and you're pushing too much air. Acceleration is another key factor, slower is better. Enterance ramps are a whole different ballgame, though. When I lived down in Houston I ALWAYS tried to merge at speed. Fuel economy takes second fiddle over a safe entry onto the freeway.