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

I am of the same thought with you, Mello Mike and CumminsDriver. I guess some folks will argue to not make changes to your truck because the truck engineers are all knowing, then want to play "scientific research" with tire pressure. My bet is the tire manufactures ram millions of dollars testing their tires under various conditions. To imply their charts on their tire pressures incorrect is not "scientific research" in my opinion.

Let there be no question, I will modify just about everything on my truck, including tire/wheel size. That said, I will follow a tire manufactures (not tire store) on the psi.

My bet is that most folks have no idea as to why there is a minimum psi on the 19.5 tires.

Wayne

Several years ago, my company truck was a 2002 F450 with the 225/19.5 tires. The tires had a sidewall max pressure rating of 110 psi, and the door sticker from Ford had a max psi of 75 at all 4 corners. The dual rear was a Dana 80 and was rated at 11,000 lbs with the 225/19.5 tires at 75 psi. No need to go higher than 75 psi as that was all the pressure needed to handle 11,000 lbs. I was only running the truck at about 9000 lbs on the rear axle, so I was still over pressure for the load but it was not recommended to run lower than 75 psi on the 19.5's.

I did the same on my dually with my camper, 65 psi in the dual rears which was rated up to 9350 lbs at that pressure. Never had a squishy sidewall or tires rubbing either.

Rich

Reddog1 wrote:
Sometimes I gotta shake my head wondering how some folks think. My rear axle weighs 6200 lbs, the front is 4200 pounds. The maximum PSI on my tires is 120 PSI.

For those of you that are of the belief you should run the maximum pressure the tire is capable of, how would you explain this chart from Michelin?



I am of the belief the PSI is determined by the load on the tires. In my case, 75 psi and not 120 psi. I don't think I should run lower than the 75 psi, due to the tire design and the design of the Vision aluminum wheels. Actually, if my memory is correct, Michelin recommends no less than 75 psi.

A couple of times I aired up to 120 psi. Without the TC, my truck felt as though it had no springs or shocks. It bounced like a ping pong ball.

Perhaps your truck/TC and tire/wheel combo should run the maximum psi. To simply believe the maximum psi on the tire is what you should run is incorrect, in my opinion. I suggest you weigh your axles, then check with the tire manufacture for the proper psi. I will add, with all due respect, the tire store typically does not have a clue on psi, and more often than not put the maximum psi as indicated on the tire.

Wayne

I agree with you, Wayne. Air up your tires based on the load. It's crazy to run 80 PSI, or max air pressure, all the time. Based upon my weights at the scales I run 80 PSI back and 60 PSI front when my camper is loaded. Unloaded, I run 60/60, though my rear can go even lower than that.

And a rule of thumb to tell if you might be in trouble with the inflation pressure you've chosen:

You do NOT want any more than a 10% pressure build up. So if you start with 80 psi, the maximum you should want to see is 88 psi - lower is better.

If you see between 10% and 15%, you should be concerned and take some steps to get the value below 10%.

But if you see 15%, you need to take immediate action. not tomorrow. NOW!

The typical remedy is adding pressure. A recommendation is to add the amount of the build up (on top of what is already there) - keeping in mind where you start so you don't exceed the tire's max.

Another way to deal with the problem is to slow down.

2oldman, I got yer back! ;)

tire pressure?

In my work I always used the "Scientific Method" to construct and operate experiments. ( Click here, explaination of the scientific method )

Basically... you look at the problem, you think about the possible solutions and choose what you think might be the best one... then, you make only one change and evaluate the results... then and only then:

If you accepted the first change you might see if you can make the solution even better by adding another change and then evaluating it. Some times you can make things better by removing something.

I see people adding a ton of miscellaneous "stuff" to their trucks without testing any of these add-ons in an attempt to make the truck better... some might help, some of the stuff will work againest some of the other stuff being added... some won't help at all.

The US Patent Office will issue a new patent for a simplier solution to a problem... or even a totally different approach to the problem... but you can't make someone elses invention more complicated and get a patent. To a scientist or researcher a US or Foriegn Patent is a real sign of acheivment.

Do you have any idea why you added each things... would advertizements lie?

Now... using the scientic method for determining the correct air pressure in your tires.

Most people will intutively get it right... over time

THey'll know what they want to acheive: they might want...

1) to haul a very heavy load

2) stability

3) sway control

40 fuel economy

5) tire longivity... good wear

6) etc

This is pretty simple:

Try putting differnent air preeures into your tires... go camping:

... if you start at the maximum air pressure listed on your tires sidewalls you eliminate all of the possible air pressures above this point.. see, the scientific method is working.

Next week... change 9lower) the pressure... go camping

third week... change the Air PSI... go to the beach

do ths every weekend... you'll have the perfect answer in time.

Isn't scientific research fun?

Note: if you are adding extra sway bars, etc at the same time you'll mess up your experiment... if you added a ton of the extras when you bought the truck you have accomplished one thing for sure... you added weight... maybe non-productive weight.

Let us know what you find to be the perfect air pressure for you... be sure and share pictures of the camping trips.

Janet and I started our experiment at 80 psi... we are still on that trip

Sleepy

Wayne, that's crazy talk. ;)

Sometimes I gotta shake my head wondering how some folks think. My rear axle weighs 6200 lbs, the front is 4200 pounds. The maximum PSI on my tires is 120 PSI.

For those of you that are of the belief you should run the maximum pressure the tire is capable of, how would you explain this chart from Michelin?



I am of the belief the PSI is determined by the load on the tires. In my case, 75 psi and not 120 psi. I don't think I should run lower than the 75 psi, due to the tire design and the design of the Vision aluminum wheels. Actually, if my memory is correct, Michelin recommends no less than 75 psi.

A couple of times I aired up to 120 psi. Without the TC, my truck felt as though it had no springs or shocks. It bounced like a ping pong ball.

Perhaps your truck/TC and tire/wheel combo should run the maximum psi. To simply believe the maximum psi on the tire is what you should run is incorrect, in my opinion. I suggest you weigh your axles, then check with the tire manufacture for the proper psi. I will add, with all due respect, the tire store typically does not have a clue on psi, and more often than not put the maximum psi as indicated on the tire.

Wayne

AS was already stated put in the maximum that the rear tires are rated for an in agreement with the manufacturer's recommendation for a DRW truck. For the front tires I would also use the manufacturer's recommended tire pressure.

If you are at the maximum the tires will do a better job in supporting the load and there will be less road sway from the camper and less sidewall flexing so less heat buildup in the tires - for a much safer ride. Nothing worse than a blowout with an inner tire on a DRW truck with a camper in the bed from both a handling perspective and in terms of having to change the tire.

Heavy duty trucks are engineered to carry a heavy load as are the rims and tires provided by the factory. No reason to not go with the factory specs. Not only safer but you will get longer tread life as well.

as I'm a memeber of the max pressure club even my ecno box focus hatchback has max pressure in the tires...comes in handy when you get to make a stop out of the blue and pick up 5/6 hundred lbs of semi parts.. biggest thing you'll notice is the ride is stiffer and less squirm from the tires and even if you have more capicity than needed is better than being uninflated in my book