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Old 08-23-2018, 01:58 PM   #1
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2016 27' International
Orlando , Florida
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Tire Inflation advice

Hello Roger,

I hope you will help me. I am looking for a recommendation for tire inflation on my TV and TT. There are tons of posts with different opinions on what to do. I am an AS newbie and just want to run safely.

All tire ratings came from the Michelin's (Toyo) inflation chart so you would not need to look them up. All tires are new.

TV - 2016 F150 Super Crew GVWR 7000 lbs (1750 per tire) with 18" wheels and Michelin Defender LTX M/S LT275/65R18 load range E. I also have an Equalizer E4 WDH.

3415 lbs at 80 psi
3000 lbs at 65 psi
2535 lbs at 50 psi
1940 lbs at 35 psi


TT AS 2016 AS 27FB International 7600 GVWR. (1900 per tire). I have upgraded to 16" Sendel wheels with Michelin Defender LTX M/S LT225/75R16 load range E

2470 lbs at 80 psi
2150 lbs at 65 psi (Current pressure)
1765 lbs at 50 psi

Any advice on what they should be to be safe I would appreciate very much. Going on our first trip from FL to the Smokie mountains next week.

Thank you in advance
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Old 08-23-2018, 03:06 PM   #2
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I would find a moving company with a public scale, get my rig(s) close to final towing weights and have them weighed. With total GVW, I would be able to determine what my tire inflation pressures needed to be. I'd run 75-80(cold) in the Ford and use GVW of the AS to determine final cold pressure on it.

May I suggest a ride on GSMR.com if you've never been. Lots of things to enjoy at Pigeon Forge & Gatlinburg.

Good Luck and Enjoy!!
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Old 08-23-2018, 04:19 PM   #3
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Stock tires on my '17 F250, door jamb sticker says 70psi front, 75psi back, that's what I run.

Stock tires on '19 International, 80psi all around.
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Old 08-23-2018, 04:20 PM   #4
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Hi

If you *really* want to do it right, you need to weight each wheel individually each morning after everything (and everybody) is loaded up. You then need a tire pressure chart that is corrected for your local temperature. Each tire then gets exactly (to the tenth of a pound) the right pressure for that day. Doing this will extend the life of your tires by at least a couple hundred miles

Indeed you can go a bit nuts with this sort of thing. No sane person would ever weigh each tire every morning. Assuming you are a normal traveler, that's what you would need to do. One day you have a full load of water, the next day the tanks are dry. One day you are towing with your TV, the next day the trailer is parked. If indeed you *are* someone who always has *exactly* the same stuff in the same locations every time you move, I'm amazed ....

So what to do?

Run over a CAT scale and see where you are at. There are a lot of reasons to do that. Tire pressure is fairly far down the list. From that data, make a guess at your typical loads. Use that for your pressures. Accept that you will be off by 5 pounds one way or the other. Yes, your tires will wear a bit quicker. Most trailer tires die of old age rather than tread wear ....

Bob
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Old 08-23-2018, 04:27 PM   #5
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Quote:
Originally Posted by gblackburn View Post
Hello Roger,

I hope you will help me. I am looking for a recommendation for tire inflation on my TV and TT. There are tons of posts with different opinions on what to do. I am an AS newbie and just want to run safely.

All tire ratings came from the Michelin's (Toyo) inflation chart so you would not need to look them up. All tires are new.

TV - 2016 F150 Super Crew GVWR 7000 lbs (1750 per tire) with 18" wheels and Michelin Defender LTX M/S LT275/65R18 load range E. I also have an Equalizer E4 WDH.

3415 lbs at 80 psi
3000 lbs at 65 psi
2535 lbs at 50 psi
1940 lbs at 35 psi


TT AS 2016 AS 27FB International 7600 GVWR. (1900 per tire). I have upgraded to 16" Sendel wheels with Michelin Defender LTX M/S LT225/75R16 load range E

2470 lbs at 80 psi
2150 lbs at 65 psi (Current pressure)
1765 lbs at 50 psi

Any advice on what they should be to be safe I would appreciate very much. Going on our first trip from FL to the Smokie mountains next week.

Thank you in advance

First off. you lucked out that I came back to check my email and saw the notice from Airstream. People need to remember I am just a "user" of this foumas you are.


Now to your questions.


TV What is the GAWR F & R? GAWR is almost never GVWR/4.

What does your certification lable say for inflation F & R


TT What is the GAWR F & R? GAWR is almost never GVWR/4
What does your certification lable say for inflation?


I can guess but would like some more facts first.


NOTE I write a RV Tire Safety Blog and post my email on the right under my picture. I do try and check my email a couple times a day even thought the "Boss" thinks I spend too much time on the computer.
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Old 08-24-2018, 07:08 AM   #6
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More info for Inflation advice

Thanks for checking your email.
I really appreciate it!!

TV GAWR Front is 3525
TV GAWR Rear is 3800
Cert on TV with 275/55R20 (OEM tires) says 35psi but I have changed tires

TT GAWR Front and Rear is 3800 lbs.
Cert on TT (AS 27FB) says 65psi for ST225/75R15LRD but I have changed tires.
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Old 08-24-2018, 07:14 AM   #7
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Quote:
Originally Posted by gblackburn View Post
Thanks for checking your email.
I really appreciate it!!

TV GAWR Front is 3525
TV GAWR Rear is 3800
Cert on TV with 275/55R20 (OEM tires) says 35psi but I have changed tires

TT GAWR Front and Rear is 3800 lbs.
Cert on TT (AS 27FB) says 65psi for ST225/75R15LRD but I have changed tires.
What did you change them to? The pressure recommendation would be dependent on that!

And just an FYI: If you are looking for the standard answer for tire pressure - use what is written on the vehicle tire placard - if you are using the size written there! That's a good starting point if you don't know what you are doing. On your tow vehicle, the placard will be on the driver's door frame (on vehicles produced after 2008!) and for a trailer, it's somewhere on the front (I'm not sure the location is defined more precisely than that!)
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Old 08-24-2018, 12:45 PM   #8
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In the original post:

TV - 2016 F150 Super Crew GVWR 7000 lbs (1750 per tire) with 18" wheels and Michelin Defender LTX M/S LT275/65R18 load range E. I also have an Equalizer E4 WDH.

3415 lbs at 80 psi
3000 lbs at 65 psi
2535 lbs at 50 psi
1940 lbs at 35 psi


TT AS 2016 AS 27FB International 7600 GVWR. (1900 per tire). I have upgraded to 16" Sendel wheels with Michelin Defender LTX M/S LT225/75R16 load range E

2470 lbs at 80 psi
2150 lbs at 65 psi (Current pressure)
1765 lbs at 50 psi
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Old 08-25-2018, 07:17 AM   #9
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Quote:
Originally Posted by gblackburn View Post
In the original post: …….
Opps! Missed that!

The procedure that I use (and dare I say it - other tire and vehicle engineers) is to match the original load carrying capacity of the specified tires at the specified pressure. Below is the post that had that information:

Quote:
Originally Posted by gblackburn View Post
...….
TV GAWR Front is 3525
TV GAWR Rear is 3800
Cert on TV with 275/55R20 (OEM tires) says 35psi but I have changed tires

TT GAWR Front and Rear is 3800 lbs.
Cert on TT (AS 27FB) says 65psi for ST225/75R15LRD but I have changed tires.
Tow vehicle: A P275/55R20 at 35 psi has a load carrying capacity of 2185# (Note the reduction by 1.10 for use on a truck!)

Trailer: An ST225/75R15 at 65 psi has a load carrying capacity of 2540# (65 mph speed restriction).

Now the current tires:

Quote:
Originally Posted by gblackburn View Post
…….
TV - 2016 F150 Super Crew GVWR 7000 lbs (1750 per tire) with 18" wheels and Michelin Defender LTX M/S LT275/65R18 load range E. I also have an Equalizer E4 WDH.

3415 lbs at 80 psi
3000 lbs at 65 psi
2535 lbs at 50 psi
1940 lbs at 35 psi


TT AS 2016 AS 27FB International 7600 GVWR. (1900 per tire). I have upgraded to 16" Sendel wheels with Michelin Defender LTX M/S LT225/75R16 load range E

2470 lbs at 80 psi
2150 lbs at 65 psi (Current pressure)
1765 lbs at 50 psi
In order to carry the same load a P275/55R20 does at 35 psi, an LT275/65R18 needs to use [[drumroll!!]] 42 psi.


And in order to carry the same load an ST225/75R15 does at 65 psi, an LT225/75R16 needs to use [[Another drumroll!!]] 75 psi. (Note that this pressure removes the speed restriction - which I think is appropriate here!)


Please note that the above assumes all the information given was correct and that there is no additional information known - such as the actual loads on the tires.


Comments: I find it interesting that Ford specifies the same pressure front and rear, even though the GAWR's are different. This means that Ford is specifying an 81% front/ 87% rear GAWR. Put another way: They are specifying a 19% front/ 13% rear reserve capacity for this vehicle.
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Old 08-25-2018, 08:12 AM   #10
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Quote:
Originally Posted by CapriRacer View Post
Opps! Missed that!

The procedure that I use (and dare I say it - other tire and vehicle engineers) is to match the original load carrying capacity of the specified tires at the specified pressure. Below is the post that had that information:

Tow vehicle: A P275/55R20 at 35 psi has a load carrying capacity of 2185# (Note the reduction by 1.10 for use on a truck!)

Trailer: An ST225/75R15 at 65 psi has a load carrying capacity of 2540# (65 mph speed restriction).

Now the current tires:

In order to carry the same load a P275/55R20 does at 35 psi, an LT275/65R18 needs to use [[drumroll!!]] 42 psi.

And in order to carry the same load an ST225/75R15 does at 65 psi, an LT225/75R16 needs to use [[Another drumroll!!]] 75 psi. (Note that this pressure removes the speed restriction - which I think is appropriate here!)

Please note that the above assumes all the information given was correct and that there is no additional information known - such as the actual loads on the tires.

Comments: I find it interesting that Ford specifies the same pressure front and rear, even though the GAWR's are different. This means that Ford is specifying an 81% front/ 87% rear GAWR. Put another way: They are specifying a 19% front/ 13% rear reserve capacity for this vehicle.

Barry, Thanks for jumping in. I am currently involved in a tire project that is consuming a lot of my time. I think your answer is good.


Observation on Ford's suggested pressure. While it is true that the tire pressure must be capable of supporting the expected load OE engineers also have other goals they consider such as fuel economy, braking distance and stability, steering response, noise and as you know the list can go on and on. Who knows what the Ford evaluators were looking for when they selected the OE tires. ( really wonder when I see these large rim diameters on trucks. Makes me think they want a "toy truck look")


I hope this answers the OP questions.
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Old 08-25-2018, 08:36 PM   #11
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A big Thanks, to CapriRacer and Tireman9,

I will make the changes and let you know how our trip to the Smokies goes.
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Old 08-26-2018, 06:35 AM   #12
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Originally Posted by gblackburn View Post
A big Thanks, to CapriRacer and Tireman9,

I will make the changes and let you know how our trip to the Smokies goes.
You are welcome. May I suggest you also monitor your pressure buildup.

First, I recommend everyone have a check list and one of those items ought to be a tire check - both pressure and condition - and part of the condition check should be to rub a GLOVED!! hand over the circumference of the tread to check for bulges. A bulge is a sign of an impending failure. That tire would need to be replaced IMMEDIATELY.

Now for the second part of the pressure buildup monitoring. After an hour or so of highway driving, check the pressures again. You don't want to see more than a 10% buildup. If you see more, then slow down. You need to increase the load carrying capacity of the tire by either adding more inflation pressure or by getting a larger tire (load carrying capacity-wise.)

If you see more than 15% - STOP. You need to take immediate action. Slowing down in the short term, and a tire change (pressure or larger tire) shortly (We are talking days, not months!)
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Old 08-26-2018, 07:30 AM   #13
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Originally Posted by CapriRacer View Post
You are welcome. May I suggest you also monitor your pressure buildup.

First, I recommend everyone have a check list and one of those items ought to be a tire check - both pressure and condition - and part of the condition check should be to rub a GLOVED!! hand over the circumference of the tread to check for bulges. A bulge is a sign of an impending failure. That tire would need to be replaced IMMEDIATELY.

Now for the second part of the pressure buildup monitoring. After an hour or so of highway driving, check the pressures again. You don't want to see more than a 10% buildup. If you see more, then slow down. You need to increase the load carrying capacity of the tire by either adding more inflation pressure or by getting a larger tire (load carrying capacity-wise.)

If you see more than 15% - STOP. You need to take immediate action. Slowing down in the short term, and a tire change (pressure or larger tire) shortly (We are talking days, not months!)
Sounds like great advice! I will do that. I also got a TST TPMS for both the TT & TV. We leave next Saturday and getting everything ready. Again thanks for all the great advice.
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