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post #1 of 17 (permalink) Old 02-24-2009, 06:42 AM Thread Starter
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285 tire pressure

285/75/16 BFG AT Ko's

should I adjust the pressure different from the oem 265's

door sticker states 55 in the front , 70 in the rear. I always drop the rear pressure if I'm not towing to about 55 and back up to 70 when in tow.

the tire says 80lbs max.

16x8 wheels,thanks in advance.
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post #2 of 17 (permalink) Old 02-24-2009, 09:25 AM
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First, you need to weigh the rig to get front and rear axle weights, once when "unloaded" but with your normal stuff when not towing, and once when loaded for bear with the trailer hooked on.

Then use a load/inflation table for your exact size tire.

Here's the load/inflation table for LT285/75R16 tires, regardless of brand:

PSI. max weight capacity
--- . ---------------------
35 . 2,130
40 . 2,340
45 . 2,540
50 . 2,755
55 . 2,925
60 . 3,110
65 . 3,305

So if your truck weighs 4,100 on the front axle and 3,900 on the rear axle when not towing, that's 2,050 on each front tire and 1,950 on each rear tire, so you need 35 PSI front and rear.

When loaded for bear, you might have 4,800 on the front axle and 5,200 on the rear axle. So for that condition you'd need 45 front and 50 rear.

You should never need 70 PSI in the rear tires. That would be well over 6,610 pounds on the rear axle or over 11,600 on the 4 truck tires. I hope you don't overload your truck that much.





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My Sierra Blanca (Spanish for White Mountain) in the sig pic was a great pickup for 11.5 years. I sold it several years ago. I drove a hand-me-down 2003 F-150 SuperCrew 4.6L 2V for a while, but it was unacceptable for towing more than a rowboat. Replacement is a 2012 F-150 EcoBoost SuperCrew Lariat that tows my 5,000-pound TT like a dream. Replaced the 2012 with a 2019 F-150 3.5L EcoBoost with max tow.

Last edited by SmokeyWren; 02-24-2009 at 09:40 AM. Reason: clarify
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post #3 of 17 (permalink) Old 02-24-2009, 09:29 AM
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I run 55psi empty in my 285 LRE's

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post #4 of 17 (permalink) Old 02-24-2009, 09:49 AM
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Quote:
Originally Posted by kidder View Post
I run 55psi empty in my 285 LRE's
55 PSI will support 5,850 pounds on each axle. If you have 5,850 pounds on the rear axle, you'll probably have over 5,000 on the front axle, for a GVW of over 10,850 pounds. That's overloaded for a '99-'04 F-350 SRW. So you should not need to add more air when you hook up a trailer or haul some weight in the bed. And you'll never need 55 PSI in the front tires unless you are severely overloaded.



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post #5 of 17 (permalink) Old 02-24-2009, 06:34 PM
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Let me get this right...you are saying that Ford (and tire company) engineers are all idiots and that they should just put 45psi in the tires and not pay attention to the recommended inflation pressure sticker or the writing on the sidewall of the tire that tells you its specific weight capacity and the pressure that this capacity is valid at?

Surely Ford would have opted to run 45 in them as it would make the ride a lot smoother...unless they wanted it to ride rougher and be more manly for whatever reason.
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post #6 of 17 (permalink) Old 02-24-2009, 07:48 PM
 
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Quote:
Originally Posted by SmokeyWren View Post
55 PSI will support 5,850 pounds on each axle. If you have 5,850 pounds on the rear axle, you'll probably have over 5,000 on the front axle, for a GVW of over 10,850 pounds. That's overloaded for a '99-'04 F-350 SRW. So you should not need to add more air when you hook up a trailer or haul some weight in the bed. And you'll never need 55 PSI in the front tires unless you are severely overloaded.
That's a pretty gross generalization of tires and air pressures. You can take two different brands of tires, two different styles, and they will respond incredibly different to air pressure, disregarding loads above an empty truck.

edit: I have 285/75/16 Cooper Discoverer STT's on my truck. They are only a D load rating. You can buy 285/75/16 Toyo Open Country MT's, with an E load rating. That's a pretty serious difference in payload, regardless of air pressure.

Last edited by wafreeskier; 02-24-2009 at 07:54 PM.
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post #7 of 17 (permalink) Old 02-24-2009, 08:37 PM
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Quote:
Originally Posted by drewkeen View Post
Let me get this right...you are saying that Ford (and tire company) engineers are all idiots and that they should just put 45psi in the tires and not pay attention to the recommended inflation pressure sticker or the writing on the sidewall of the tire that tells you its specific weight capacity and the pressure that this capacity is valid at?
No, the tire company engineers are the ones that developed the load/inflation tables, through their association, the Tire and Rim Assn(TRA). The TRA develops the numbers, and publishes them in their annual report to members. All the tire company engineers know exactly what the load/inflation tables say. And they agree with them.

But they are complicated, with lots of ifs, ands and buts. So how do you educate the public?

But then the lawyers get involved, and the engineers get overruled by "management" afraid of lawsuits. Some tire companies don't even publish the load/inflation tables. They fall back on the excuse that you should do what the vehicle manufacturer suggests. Then if you want to sue somebody, you can sue Ford, but not Michelin.

The vehicle manufacturer puts only one number on the door sticker, and that number assumes you have loaded the vehicle to the max. So if your door sticker says 55 front and 70 rear, that's only when you are loaded to the GVWR of the vehicle, or in some cases loaded to the front and rear GAWR of the vehicle. When you are loaded to less than GVWR (or GAWRs), you can safely put less air in the tires. How much less? That's what the load/inflation table tells you.

The tire manufacturer cannot print the entire load/inflation table on the sidewall. So they print only the max weight and the PSI needed to have that weight capacity. That's doesn't mean the tire company engineers are idiots. They all know exactly what the load/inflation tables say.

But management assumes all customers are idiots. They hope you will pump up your tires to the max on the sidewall, because too much PSI is safer than not enough. But informed customers know about the load/inflation tables, and use them.

Here is some 'portant poop from Goodyear, which Goodyear reprinted from the TRA annual report. Study it and use it and your truck will ride better and your tires will last longer.
Goodyear Load/Inflation tables

That's a 19-page PDF file. The load/inflation table for the LT285/75R16 is on page 7 of 19 per Adobe Reader. Compare the "Single" line to the table I posted earlier and you'll see I didn't pull those numbers out of my rear end.

Also note that Goodyear's tables only include the tire sizes that Goodyear sells. You won't find huge donuts in those tables, because Goodyear doesn't market huge donuts.

But Toyo does. Look around on the Toyo website, and you'll probably find the load/inflation tables posted by Toyo for the sizes of LT tires they market.

Here are some of the TRA tables from a few years ago:
TRA load/inflation tables

That's a 32-page PDF file, and the load/inflation tables begin on page 21.

By the way, all load/inflation tables for the same size tire will be identical - taken from the same page of the TRA annual report. So if you can find a Goodyear load/inflation for size LT285/75R16, then you know that table will be good for a Michelin or BFGoodrich or Toyo LT tire of the same size.

You homework for tomorrow: My front axle weighs 4,440 pounds and my rear axle weighs 5,180 pounds. My tires are size LT235/85R16E. I tow at 62 MPH going cross-country from Texas to New York and return. What should my tire pressure be on my tow vehicle?

Class dismissed for today.



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post #8 of 17 (permalink) Old 02-26-2009, 08:22 AM
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What? Nobody showed up for class today?

I guess most folks get bored if the answer is complicated.



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post #9 of 17 (permalink) Old 02-26-2009, 10:41 AM
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Actually printed some of the data and placed in glovebox.

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post #10 of 17 (permalink) Old 02-26-2009, 01:55 PM
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I don't have anything but experiance to back me up, but I run 60 psi in my 285/75/R16 BFG K/O's at all times. I have over 180,000 miles on this truck, and seem to get the best wear out of them at 60. (that's several sets of BFG's)

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post #11 of 17 (permalink) Old 02-26-2009, 07:36 PM
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I have a cc, lwb, 4x4 and run BFG AT 285/75s E Range.

I run them at 75 front and 80 rear and they run great. I have a trailer hooked up about 60% of the time. The wear has been great.

Now when I went cross country 2 mos ago - they rode like crap - so down they went to 70 all the way around.

Any lower and they feel sloppy and they wear os more pronounced.

Truck weighs about 8200 wet.

At 70 psi - I get 95% contact patch.

Just don't go below 50 or above 80 cold. i always keep more in the rear - handles better. You are going to have to experiment as every truck is going to be different depending on springs, shocks, sway bars, etc...


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post #12 of 17 (permalink) Old 05-08-2019, 08:31 AM
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I run whatever pressure I need depending upon how much weight I have on board--up to the MAX listed on the sidewall if needed. I DO, however air the tires down when not carrying anything significantly heavy to keep the ride reasonable. If I have the tires aired up to or near MAX listed pressures, they (pretty much every brand I have tried) seem to make the ride pretty danged stiff/hard. Airing them down to a reasonable daily driving pressure will ease the ride some, but I WILL SAY that you need to keep an eye on the wear pattern to be sure you haven't gone TOO LOW on the pressure and also to some little "tests" to see how the truck responds to quick steering inputs. I also make a habit of walking around the ruck putting my open palm on each tire just to sorta keep tabs on temps every time I have changed pressures and have driven more than about 10-15 minutes. Experience will help you zero in on what works best for your truck, your weights, and whichever brand and tire size you run. This is all MY experience and it works for me----and so YMMV!!

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post #13 of 17 (permalink) Old 05-09-2019, 07:56 AM
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Why does a wheel alignment shop fill the tires to the maximum rating before checking the alignment?

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post #14 of 17 (permalink) Old 05-09-2019, 08:37 AM
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No clue...they should be aligning off the wheels, not the tires.

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post #15 of 17 (permalink) Old 05-09-2019, 01:27 PM
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Quote:
Originally Posted by SmokeyWren View Post
Here is some 'portant poop from Goodyear, which Goodyear reprinted from the TRA annual report. Study it and use it and your truck will ride better and your tires will last longer.
Goodyear Load/Inflation tables
This thread is over10 years old, and lots of water has run under the bridge since then. When I click on that link today, then on "resoures" I get the following:

"Industry standards for load and inflation are in a state of change in a move toward global standardization. Goodyear is continuously updating its product line to move to these new load and inflation standards. As such, any printed material may not reflect the most current load and inflation information."

And I don't find any load/inflation tables on the Goodyear website today. So without being a member of TRA (which is a very expensive membership), I don't know how to find current load/inflation tables. The 2017 version of the TRA Load/Inflation tables is still available on ToyoTires.com, but they hide it really good. Here is the link to the 31-page PDF file that includes size LT285/75R16 on page 21. https://www.toyotires.com/media/2125...s_20170203.pdf


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My Sierra Blanca (Spanish for White Mountain) in the sig pic was a great pickup for 11.5 years. I sold it several years ago. I drove a hand-me-down 2003 F-150 SuperCrew 4.6L 2V for a while, but it was unacceptable for towing more than a rowboat. Replacement is a 2012 F-150 EcoBoost SuperCrew Lariat that tows my 5,000-pound TT like a dream. Replaced the 2012 with a 2019 F-150 3.5L EcoBoost with max tow.

Last edited by SmokeyWren; 05-10-2019 at 09:04 PM. Reason: Add Toyo load/inflation table
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