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Old 09-28-2010, 01:56 PM   #1
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Wondering what you guys are running for air pressure in your tires. Are you running with full cold psi? I am use to a class A where you weigh the four corners and look at a chart to determine what psi you should run with.

My steer tires is max 120 lbs cold
Rears 110 lbs cold.
I am thinking I should air up to the max but wonder what you guys are doing.

Thanks
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Old 09-28-2010, 02:17 PM   #2
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Eds,

The only correct way to get the answer to your question - relative to your truck - is too look up the tire pressure / weight chart from your tire manufacturer. Look at the specific load for each tire position and determine the correct pressure from the chart.

Personally I am at max of 12K lbs on the front axel and run 120psi in the front but only 85psi each in the 8-rear tires. I should also add that along with safety, PSI per tire affects ride quality a great deal. When we picked my coach up from the Tire Dude he had all 10 at 120psi and well...it rode like a truck. A few moments with BF Goodrich load charts and the world inside our coach was a much nicer place while underway.

Rad
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Old 09-28-2010, 02:33 PM   #3
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I was thinking t/c's would be different than class A motorhomes when it comes to setting your tire pressure. I think of the semi drivers who do not change their tire pressure every time they change loads.

I did bump my steer tires up by 10 lbs and did not notice any real change in ride. Right now for the most part I think I am 10 lbs under max cold ratings in all.

I also think if the tires are not inflated enough you damage the side walls. Just would think going with the max cold would be best for the tires and mpg. But I can be wrong in my thinking.
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Old 09-28-2010, 03:16 PM   #4
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OK, according to Micelins load and inflation chart I should be a t max 120 on the steer since I am carring 15,000 plus up front. 20,000# axel.

Backs I am not real sure about since they do not have a chart for truck with a tag but I may try full pressure back there as well or 5# under.
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Old 09-28-2010, 03:21 PM   #5
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You can't really go wrong with the manufacturer’s recommendations. If they say at X lbs run Y PSI then you won’t damage the tire and you should get the best compromise between gas mileage, tire life and comfort from your tires. You may get better mileage from running overinflated but you’re likely to wear the center of the tire more quickly and ride quality will suffer.

We are roughly at a “fixed load” and that makes it easier to take advantage of choosing and maintaining the correct pressure for the tire based on load.

http://www.bfgoodrichtrucktire...eInfo.do?tread=DR444

Go here and you can see how much pressures can change based on the load for the 275/80R22.5 DR444.

16,380lbs per axel / running duals = 70psi while max load is achieved at 110lbs

I think this is the best advise you can get...right from the engineers that build them.

But thats just my opinion...there will be more.

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Old 09-28-2010, 03:56 PM   #6
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Oh noooooooooooo,, tire pressure ? I like that BF Goodrich link Rad. Interesting. I've kind of taken the position that the max pressure listed on the sidewall is what I like. If the tire maker says this tire will hold 110 lbs when cold, then that's what it will hold. Now, read further on the sidewall (or before the pressure wherever it's listed) and it will say the max weight/load the tire will hold up. So, I suppose you could lower the pressure if you had a lighter load than that max. But, why? To make it ride smoother I suppose. Would a harder (higher pressure) tire get better mileage? I think it would. Would a harder tire deflect the sidewall less, thereby offering better handling when cornering? I think it might. Another question: the more a tire flexes side to side, the more heat is generated, thereby causing more pressure fluctuation and wear? I don't know. I think tire pressures seem to always generate a bunch of different answers depending on whom you talk to. It's a great question, just figure everybody has their reasons for what they like. I'm a max posted guy. But I like the firm ride and good handling. I always check my tires before moving it so they're cold.
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Old 09-29-2010, 07:24 AM   #7
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Bob,
Whatever works for you is OK by me.

Consider the following:
• MAX means maximum pressure that the tire “requires” to hold the maximum rated load more so than MAX pressure it will hold, but I get what you mean
• A harder tire (higher pressure) will give you less roll resistance and may result in better mileage
• Over inflated tires:
May not give you better handling as they wont not conform to the surface of the road as well as a properly inflated tire (by the book). Result = less traction / smaller foot print
May put higher pressures on the center of the tire and wear unevenly across the tread surface (center first) Result = shorter tread / tire life
Sidewalls will not deflect as much as properly inflated tires. However tire side walls are designed to deflect to absorb irregularities in the road surface. This is the first element in your trucks suspension to absorb small irregularities and reduce shocks transferred from the road to the trucks chassis and sub-systems (mechanical and electrical) that shorten the life of the whole rig

Over inflated tires are much safer than under inflated tires.
I believe that most fleet and many independent drivers don’t want to mess with the charts and feel “it’s better to be safe than sorry” so avoid the mistakes in calculating loads and reading charts, just pump-em up to the max.

In the TC / RV world we have a relatively static load and it is much easier to make the calculations and follow the manufacturers’ recommendations to operate within the tire’s designed performance envelop to achieve best traction, longest wear, highest ride quality and of course - safety.

I guess that means I am an “adjust the pressure to meet the load guy”

Rad
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Old 09-29-2010, 07:44 AM   #8
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Bob, I am a big believer in the proper inflation for the job at hand. If you look at the door jamb on most cars, they will have a psi for different weights (depending on passengers etc). under/over inflation can wear out the tires too quickly. Under can wear out the sides, but over can cup the tread and wear out the tread center. Under gives better traction, and over gives better mileage. If there is not a psi rating for the job at hand, I look at the profile of the tire and make a judgment call. I make sure that the tread is flat on the ground and the side walls are sitting up properly. My hot rods never have multiple psi settings, so I had to learn how to "judge" it.

That's how I do it
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Old 10-04-2010, 05:48 AM   #9
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Max air pressure in tires for this past weekend show in Freeport, IL. Ride was good and I think it handled better with more air. The road between Madison and Rockford has always been a rough one though. Going to keep them at max 120 and 110 pounds.
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Old 10-04-2010, 06:41 AM   #10
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I've got another one for you. I checked around that BFGoodrich site. Their different tire models appear to have different pressures on the charts. Now, most of my tires don't match each other. I've got several different tires. I know, not the best. I'd love to have all the same tires, at least even axle matches. But I don't. So, should I figure out what tire is where and use each tire manufacturer's chart and air each tire accordingly? I'm not messing around with that. I'm way too lazy for that. I'll just keep using the max as I've always done. Works great for me. I've never had a tire fail except for punctures. And I don't think I've ever worn out a tread either. My tires always seem to need replacement due to age as far as I can remember.
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