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Old 09-25-2023, 11:03 PM   #1
thomseninc
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What is the max safe cold tire pressure?

At the MOC rally I had my F-250 and 3231CK weighed by the RVSEF crew. I was told the tires on the rear axle of the F-250 were underinflated for the load they were carrying. I have been inflating them to the max cold number on the yellow placard in the door jam (65 psi), but was told (err, suggested) that they be inflated to 80 psi. When I got home I asked the Ford dealer truck guys their opinion on if it was safe to run the rears at 15 psi over the number on the sidewall and they suggested I ask the Michelin guys for guidance. I called Michelin and spoke with their tech guys. They suggested I ask Ford (when did all of the tech guys turn into lawyers?) So, I’m going to ask my MOC friends for your opinion (no lawyers need respond): run at 65 psi ( 3195 lb load rated vs 3600 lb measured), or run at 80 psi (enough load capacity, but 15 psi over the sidewall number)? Or split the difference (72-73). FWIW, I have put around 5K miles on the rig with the rears at 65 psi.
 
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Old 09-26-2023, 03:48 AM   #2
Lee-CI
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When I ran a ¾ ton TV I always ran 80 psi all the way around because that is what was stamped on the tire sidewalls for cold inflation pressures. I'm still running 80 psi cold pressures on the steer axle tires on the DRW dually.

The RVSEF folks aren't going to suggest dangerous information.
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Old 09-26-2023, 06:01 AM   #3
RMcNeal
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I'm towing with an F350 but my tire inflation placard show 65psi front and 80psi rear. It came stock with Michelin tires, but I have replaced them several times over now and I'm running Good Year Wrangler AT's with kevlar side walls.
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Old 09-26-2023, 06:07 AM   #4
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sounds like you need more truck
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Old 09-26-2023, 07:41 AM   #5
Rotnjonny
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Ever since Ford had the “Firestone Fiasco”, the dealers have become very guarded in their comments regarding tire pressures. The tire manufacturers PSI are based upon how the tire is built / manufactured. The sticker on the door is based upon how the vehicle was built and tested. I use the tire manufacturer’s data as my maximum pressure and the truck manufacturers data as my minimum inflation. For what its worth, I run 75psi in mine
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Old 09-26-2023, 07:52 AM   #6
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have run 110PSI (G Load) for years, 80PSI (E load in the truck, no issues.
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Old 09-26-2023, 08:15 AM   #7
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Now I’m the kind of guy who runs with scissors, but I would not exceed the maximum inflation pressure stamped on the tire. Ok, maybe a few pounds but certainly not 15! Get heavier duty tires. I think that the door sticker I what the manufacturer feels is the best compromise for comfort, handling, and wear.
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Old 09-26-2023, 08:17 AM   #8
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If you are running an E rated LT Truck tire on that 2500 diesel truck then the max cold inflation pressure stamped on any E rated tire is in fact 80 psi

I run 80 psi cold when towing on the rear and 55 psi cold on the rear when not towing .. 65 psi on front tires empty or loaded
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Old 09-26-2023, 08:31 AM   #9
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When pulling my camper 80 pounds front and rear. No reason to run lower. The tires will run cooler and safer carry more weight.
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Old 09-26-2023, 11:30 AM   #10
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I am really surprised an F250 would have Michelin tires with a sidewall tire pressure marked 65 psi max. What size tire? Are they E rated tires?

My door placard on my F250 and both F350s said 65 front/80 rear. Tires said 80. I ran 65 rear when not towing and 80 rear towing.
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Old 09-26-2023, 11:59 AM   #11
Carl n Susan
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I am with BB_TX. What tires are on the truck and what is the cold tire pressure number embedded on them? What year and model is your F250?

A picture of them and the yellow door sticker would help a lot.
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Old 09-26-2023, 03:21 PM   #12
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Can you give me your GAWR's.
If you are not going over that, tires dont have enaugh maxload.

But here in Europe we have for motorhomes CP tires, wich are mostly D-load AT 65 psi or AT 69 psi.
But are given on sidewall 80 psi.
The 65 psi is the referencepressure, and not the max allowed cold pressure.
The tiremaker dont support the higher then maxload, at 80 psi, but secretly they do. They are set in the market to cover the overloading on rear axle wich often on european campers ( CP stands for Camping Pneu)
There are also lists for higher then maxload at higher pressure, well known isv1. 4 times reference when standing still, and then 2x maxload allowed on tire.
1.4 times 65 psi is 91 psi. But then tires warm pressure is also 91 psi, because speed zero.

Continental groop tires give in europe 10 psi above reference pressure as maxcold pressure. So your 65 psi reference, then 75 psi maxcold.

So yes, 80 psi cold wont hurt your tire, but its not an ideal situation. Better would be tires with higher maxload, or solve the overloading.

If you give all the tire specifications I will calculate a safe pressure for it.
Need next, read from sidewall.
1. Maxload or loadindex
2. Kind of tire to determine reference pressure, most likely 65 psi.
3. Speedcode of tire. Less important, shall be above Q

Sizes would be nice, and GAWR's and GVWR, I will search back the weights you already gave.
This all so we can yudge if tires are sufficiënt.

Edit: is your given 3600 lbs the axleload or axle-end load. If axle you dont even need 65 psi, then 1800 lbs per tire.
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Old 09-26-2023, 07:32 PM   #13
bshgto
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More truck = Less worry, at the very least, heavy duty tires = higher pressures
Failure analyses has shown anything run over its design limits for very long will shorten life and eventually fail.
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Old 09-26-2023, 07:37 PM   #14
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You should have load range E tires on your truck. Run them at 80 psi when towing. You probably have a 6250 rear GAWR. Your tire max load is 6390 lbs at 80 psi. If your rear axle load is higher then that your overloaded.
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Old 09-26-2023, 07:44 PM   #15
mlh
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The max load on my 20 inch 2008 F250 tires is 3750 pounds each or 7500 pounds for both.
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Old 09-26-2023, 11:23 PM   #16
thomseninc
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Michelin LTX AT2, 275-65R20, E rated. The door sticker says 65 psi, but I just looked at the “fine print” on the sidewall and it says max load of 3750 lb at 80 psi. I think my question is answered: run at 80. Thanks to everybody for helping. I feel bad about wasting everyone’s time!
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Old 09-27-2023, 12:15 AM   #17
rohrmann
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And that 80 psi is when the tire is cold. The pressure will rise when driven, but that is normal.
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Old 09-27-2023, 02:59 AM   #18
jadatis
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Then I made you a pressure loadcapacity list with build in maximum reserve, but still acceptable comfort and gripp.

Still like to know if the axle was weighed 3600lbs or if seperate wheelload. And empty weighed or with load as you use it, so also persons in it.

Made the list in front of cold psi ( at about 70 degr F) for seperate wheelload weighed, For that 95% given of calculated wheelloadcapacity so for 1 tire. Then look back heavyest axle-end/wheel on the axle.

Behind cold psi for if axleload given, for wich 90% of calculated axleloadcapacity, so 2 tires.

Placed the 3600 lbs behind the line for axle and wheel/axle-end.

Can be used for every Maxload 1700kg/ 3748 lbs AT 80 psi ( upto 160kmph/99mph)

Heavyest / cold / axle
Axle-end/ psi / load weighed
1710 lbs/ 36 psi / 3240 lbs
1753 lbs/ 37 psi / 3321 lbs
1796 lbs/ 38 psi / 3403 lbs
1838 lbs/ 39 psi / 3484 lbs
1881 lbs/ 40 psi / 3565 lbs
1924 lbs/ 41 psi / 3646 lbs/ 3600 axleload
1967 lbs/ 42 psi / 3727 lbs
2009 lbs/ 43 psi / 3808 lbs
2052 lbs/ 44 psi / 3888 lbs
2095 lbs/ 45 psi / 3969 lbs
2137 lbs/ 46 psi / 4050 lbs
2180 lbs/ 47 psi / 4130 lbs
2222 lbs/ 48 psi / 4210 lbs
2264 lbs/ 49 psi / 4291 lbs
2307 lbs/ 50 psi / 4371 lbs
2349 lbs/ 51 psi / 4451 lbs
2391 lbs/ 52 psi / 4531 lbs
2433 lbs/ 53 psi / 4611 lbs
2476 lbs/ 54 psi / 4691 lbs
2518 lbs/ 55 psi / 4771 lbs
2560 lbs/ 56 psi / 4851 lbs
2602 lbs/ 57 psi / 4930 lbs
2644 lbs/ 58 psi / 5010 lbs
2686 lbs/ 59 psi / 5089 lbs
2728 lbs/ 60 psi / 5169 lbs
2770 lbs/ 61 psi / 5248 lbs
2812 lbs/ 62 psi / 5328 lbs
2853 lbs/ 63 psi / 5407 lbs
2895 lbs/ 64 psi / 5486 lbs
2937 lbs/ 65 psi / 5565 lbs
2979 lbs/ 66 psi / 5644 lbs
3020 lbs/ 67 psi / 5723 lbs
3062 lbs/ 68 psi / 5802 lbs
3104 lbs/ 69 psi / 5881 lbs
3145 lbs/ 70 psi / 5960 lbs
3187 lbs/ 71 psi / 6039 lbs
3229 lbs/ 72 psi / 6118 lbs
3270 lbs/ 73 psi / 6196 lbs
3312 lbs/ 74 psi / 6275 lbs
3353 lbs/ 75 psi / 6354 lbs
3395 lbs/ 76 psi / 6432 lbs
3436 lbs/ 77 psi / 6511 lbs
3477 lbs/ 78 psi / 6589 lbs
3519 lbs/ 79 psi / 6668 lbs
3560 lbs/ 80 psi / 6746 lbs/ referencepr
3601 lbs/ 81 psi / 6824 lbs/3600 wheelload
3643 lbs/ 82 psi / 6902 lbs
3684 lbs/ 83 psi / 6981 lbs
3725 lbs/ 84 psi / 7059 lbs
3766 lbs/ 85 psi / 7137 lbs
3808 lbs/ 86 psi / 7215 lbs
3849 lbs/ 87 psi / 7293 lbs
3890 lbs/ 88 psi / 7371 lbs
3931 lbs/ 89 psi / 7449 lbs
3972 lbs/ 90 psi / 7527 lbs/ sometimes also given maxcold
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Old 09-27-2023, 03:39 AM   #19
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Wasted No One's Time

Quote:
Originally Posted by thomseninc View Post
Michelin LTX AT2, 275-65R20, E rated. The door sticker says 65 psi, but I just looked at the “fine print” on the sidewall and it says max load of 3750 lb at 80 psi. I think my question is answered: run at 80. Thanks to everybody for helping. I feel bad about wasting everyone’s time!
Friend you wasted no one's time here! None of us knows everything there is to know and we each lean on one another for knowledge. Questions are welcomed here and open for.discussion. Jump in when you have questions, but also jump in when you believe you have answers. Safe travels and happy camping
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Old 09-27-2023, 10:21 AM   #20
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Quote:
Originally Posted by Lee-CI View Post
Friend you wasted no one's time here! None of us knows everything there is to know and we each lean on one another for knowledge. Questions are welcomed here and open for.discussion. Jump in when you have questions, but also jump in when you believe you have answers. Safe travels and happy camping
Agree with Lee-CI. If that was a crime we all would have been kicked off long ago.
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