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Old 06-09-2017, 10:53 PM   #1
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Tire pressures.

I have a 2017 challenger 37yt with 22.5 Michelins on it. I have no access to truck scales within 100 miles of me so I don't know what tire pressure to have. There is no sticker on the door for tire info and looking up the specs say it's 24,000 GVW. I may have 1000 pounds loaded on the rig. Anyone have a similar rig to give me a starting point. The charts I've seen have front and rear weights with the pressures accordingly, but again, I have nothing to work with. The dealer said they put 100 pounds in them. Going on a shakedown trip Monday.

Any help please ?
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Old 06-10-2017, 12:23 AM   #2
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Probably 100PSI is a safe starting point. I had 22.5's on my previous DP, it was a 41 footer and weighed more than yours, I ran between 105 and 110PSI in those.
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Old 06-10-2017, 02:36 AM   #3
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Thank you.
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Old 06-10-2017, 03:34 AM   #4
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While on your trip look for a truck stop with scales and get an accurate weight, then you'll know for sure what pressure to run.
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Old 06-10-2017, 05:31 AM   #5
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Originally Posted by rick kirby View Post
I have a 2017 challenger 37yt with 22.5 Michelins on it. I have no access to truck scales within 100 miles of me so I don't know what tire pressure to have. There is no sticker on the door for tire info and looking up the specs say it's 24,000 GVW. I may have 1000 pounds loaded on the rig. Anyone have a similar rig to give me a starting point. The charts I've seen have front and rear weights with the pressures accordingly, but again, I have nothing to work with. The dealer said they put 100 pounds in them. Going on a shakedown trip Monday.

Any help please ?
Two schools of thought;

1) Thor places a placard somewhere near the drivers seat, it lists the inflation psi for the coach, which would be the max weight its rated to. In the case of my Miramar, it's rated at 24,000 lbs. they recommend 110 PSI based on the max weight.

Ford also recommends the coach tires be inflated to this psi.

2) Michelin the tire maker recommends running the tires at a specific psi, based on the actual weight you run your coach at. Similar to when you have your front end aligned when your coach is new, they recommend you load the rig as if you were going on a trip, with all your "stuff", water in your fresh tank as well as full tank of gas.

This is the time to run across a scale, I use the DOT scale along the highway, I figure if it's accurate enough to write truckers fines, it's accurate enough for my purposes!! Using this weight, Michelin has a chart you can reference to find the recommended psi. For my Miramar 33.5, loaded with all my "stuff" plus full fuel, I weigh in around 21,000 pounds. According to the Michelin chart I should run around 85 psi If I remember right.

If you take your rig to a Ford dealer for service, they will always inflate to the placarded psi, unless you tell them otherwise.

There are also other threads here about this topic, I'm sure someone will come along and say I'm wrong or there's a better way to do it!!

Just my 2 cent worth!!
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Old 06-10-2017, 02:42 PM   #6
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Until you weigh and consult a chart, I would set them around 85-90psi. In my 2014 Challenger the sticker with all the GVWR and tire info is down low on the left side of drivers seat. Mine states a GVWR of 22,000 and cold psi of 90. Tires stamped at cold max psi of 110 if I recall correctly.

I still need to run mine across the scales. While doing the next leg of our trip I'll fuel up at a Flying J and then pay my $10 and run it across.
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Old 06-10-2017, 03:13 PM   #7
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Originally Posted by Joe-FL View Post
Until you weigh and consult a chart, I would set them around 85-90psi. In my 2014 Challenger the sticker with all the GVWR and tire info is down low on the left side of drivers seat. Mine states a GVWR of 22,000 and cold psi of 90. Tires stamped at cold max psi of 110 if I recall correctly.

I still need to run mine across the scales. While doing the next leg of our trip I'll fuel up at a Flying J and then pay my $10 and run it across.
One point on the pressure stamped on the tires is that is the maximum pressure for the tires regardless of weight. You should never exceed the pressure rating stamped on the tires.

The label in my coach recommends 90 PSI based on the GVWR which coincides with the Michelin tire inflation chart for my tires.
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Old 06-10-2017, 06:52 PM   #8
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2015 Thor ACE 30.1 tire pressures

I have tire pressure monitors. The tires are rated for 100 psi but ACE sticker wants to inflate them only to 82 PSI. As I drive, within 15 or 20 minutes, the tires will all be running at 90 to 94 PSI. I haven't run in 100 degree weather yet, so expect the tires to get to the 100 tire rating pretty quickly.
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Old 06-11-2017, 06:45 PM   #9
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Originally Posted by hames57 View Post
I have tire pressure monitors. The tires are rated for 100 psi but ACE sticker wants to inflate them only to 82 PSI. As I drive, within 15 or 20 minutes, the tires will all be running at 90 to 94 PSI. I haven't run in 100 degree weather yet, so expect the tires to get to the 100 tire rating pretty quickly.
I'm not sure if you are inflated (cold) at 82 you will see 100psi on your TPMS even in 100 degree temps. I guess it would be possible if you are running 75-80mph and the sun was beating on one side, those tires may show that much pressure. It certainly is amazing to watch the TPMS readings as you drive through different conditions though.
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Old 06-11-2017, 08:28 PM   #10
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The owners manual I downloaded today for the 2017 Challenger says "Check
tire pressure after the vehicle has been parked for at least one hour. Inflate tires to recommended pressure as indicated on the Federal Certification Label located above the Drivers area."

I won't actually have my new Challenger 37LX until Thursday so I can't look for it, sorry.

I'm also wondering about the value of purchasing and setting up a TPMS for my Challenger. Anyone have any thoughts on that?
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Old 06-11-2017, 08:43 PM   #11
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Quote:
Originally Posted by Mike in AZ View Post
The owners manual I downloaded today for the 2017 Challenger says "Check
tire pressure after the vehicle has been parked for at least one hour. Inflate tires to recommended pressure as indicated on the Federal Certification Label located above the Drivers area."

I won't actually have my new Challenger 37LX until Thursday so I can't look for it, sorry.

I'm also wondering about the value of purchasing and setting up a TPMS for my Challenger. Anyone have any thoughts on that?
I have the EEZ TPMS and use it all the time. Morning before i leave turn it on get an idea on how pressure looks if i am within a couple of pounds of my desired pressure (80) I am good if not i use my on board compressor to add whats needed while on road just glimps at it once in awhile just to see how pressure is running mainly have it as a precaution for a slow leak they are not going to help if you run over something and get a blowout
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Old 06-11-2017, 08:54 PM   #12
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Originally Posted by dcbenny View Post
I have the EEZ TPMS and use it all the time. Morning before i leave turn it on get an idea on how pressure looks if i am within a couple of pounds of my desired pressure (80) I am good if not i use my on board compressor to add whats needed while on road just glimps at it once in awhile just to see how pressure is running mainly have it as a precaution for a slow leak they are not going to help if you run over something and get a blowout
Thanks! I would think (but don't know from my own experience) that a blowout, even on an inside tire, would be noticeable, but as you said, a slower leak (like a nail or something) would give me warning before it's gone flat enough to feel it inside.
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Old 06-11-2017, 11:44 PM   #13
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Originally Posted by Joe-FL View Post
I'm not sure if you are inflated (cold) at 82 you will see 100psi on your TPMS even in 100 degree temps. I guess it would be possible if you are running 75-80mph and the sun was beating on one side, those tires may show that much pressure. It certainly is amazing to watch the TPMS readings as you drive through different conditions though.
In the Nevada desert, 100 degrees ambient air temp is upwards of 125 or so on the pavement. I'm pretty sure I'll see 100 on the psi when we head south in 10 days. If not, I'll be happy.
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Old 06-12-2017, 01:03 AM   #14
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Originally Posted by hames57 View Post
I have tire pressure monitors. The tires are rated for 100 psi but ACE sticker wants to inflate them only to 82 PSI. As I drive, within 15 or 20 minutes, the tires will all be running at 90 to 94 PSI. I haven't run in 100 degree weather yet, so expect the tires to get to the 100 tire rating pretty quickly.
This may help. As I understand it, the maximum pressure rating applies to "cold" inflation only, and it's expected that if tire started the day at maximum pressure, then it will go over that rating due to temperature. That's normal and expected as far as I know for truck tires also.

https://www.tirerack.com/tires/tiret...jsp?techid=196

It's important to note that much of the temperature rise in tires comes from within the tire due to the constant flexing of the tire, not just from ambient. Much of that energy the engine has to produce to overcome rolling resistance ends up as heat in tires. That's why the faster we drive the hotter tires get, assuming everything else remains equal.

In no case should air be bled off to lower pressure because of this. If that were done, the tire would then get hotter, eventually leading to failure. High tire temperature is usually the biggest problem.
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Old 06-12-2017, 01:33 AM   #15
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Originally Posted by Chance View Post
This may help. As I understand it, the maximum pressure rating applies to "cold" inflation only, and it's expected that if tire started the day at maximum pressure, then it will go over that rating due to temperature. That's normal and expected as far as I know for truck tires also.



https://www.tirerack.com/tires/tiret...jsp?techid=196



It's important to note that much of the temperature rise in tires comes from within the tire due to the constant flexing of the tire, not just from ambient. Much of that energy the engine has to produce to overcome rolling resistance ends up as heat in tires. That's why the faster we drive the hotter tires get, assuming everything else remains equal.



In no case should air be bled off to lower pressure because of this. If that were done, the tire would then get hotter, eventually leading to failure. High tire temperature is usually the biggest problem.


Well said the sidewall of a tire rolling is like bending a piece of metal back and forth with the correct pressure this is kept to a minimum lower the pressure and the sidewalks flex more producing more heat too low pressure and you get what is called a zipper failure
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Old 06-12-2017, 02:38 PM   #16
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Originally Posted by hames57 View Post
In the Nevada desert, 100 degrees ambient air temp is upwards of 125 or so on the pavement. I'm pretty sure I'll see 100 on the psi when we head south in 10 days. If not, I'll be happy.
Again, it will depend on more factors than the outside temperature. My fiver had G rated tires inflated to 100 psi and the highest psi rise I ever experienced was 116 psi. If your cold inflated tires at 82 psi start climbing over 100 psi then I would be surprised, But I am basing this simply on my experience with G rated fiver tires over about 45,000 miles of towing with my TPMS. I guess it really doesn't matter since most tires won't blow until above 150 or 160 degrees anyway.
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Old 06-12-2017, 02:55 PM   #17
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Originally Posted by Mike in AZ View Post
The owners manual I downloaded today for the 2017 Challenger says "Check
tire pressure after the vehicle has been parked for at least one hour. Inflate tires to recommended pressure as indicated on the Federal Certification Label located above the Drivers area."

I won't actually have my new Challenger 37LX until Thursday so I can't look for it, sorry.

I'm also wondering about the value of purchasing and setting up a TPMS for my Challenger. Anyone have any thoughts on that?
Mike, I wouldn't run down the highway without my TPMS on and working. I want to know the temp and psi of my tires, plus have the benefit of an alarm sounding if I start dropping pressure in a tire.

Just a word of caution about setting your psi initially. You can load up and run it across a scale for $10 and then consult your tire manufacturers guide for more precise psi, or go by placard in your coach. You will probably be setting them somewhere between 85 and 95. But you want to set them all when they are in the shade and at the same time. DO NOT KEEP ADJUSTING ONE OR TWO DURING A TRIP. Unless there is something wrong with one of your tires they will not bleed off pressure during a trip. If I turn on my TPMS just as the sun is coming up it shows all of my tires within 2 pounds of each other. They are all in the same temp conditions with no sun on them. Now if at 10am I start checking them I will find that the ones on the sunny side of my coach show 3 to 5 psi higher. So if I let air out of those they will be low by that much when running down the interstate. Get them set right the first time and leave them alone. Trust your TPMS. IMHO a TPMS is about the most important piece of safety equipment you can have on a larger RV.
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Old 06-12-2017, 03:05 PM   #18
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Quote:
Originally Posted by Joe-FL View Post
Mike, I wouldn't run down the highway without my TPMS on and working. I want to know the temp and psi of my tires, plus have the benefit of an alarm sounding if I start dropping pressure in a tire.

Just a word of caution about setting your psi initially. You can load up and run it across a scale for $10 and then consult your tire manufacturers guide for more precise psi, or go by placard in your coach. You will probably be setting them somewhere between 85 and 95. But you want to set them all when they are in the shade and at the same time. DO NOT KEEP ADJUSTING ONE OR TWO DURING A TRIP. Unless there is something wrong with one of your tires they will not bleed off pressure during a trip. If I turn on my TPMS just as the sun is coming up it shows all of my tires within 2 pounds of each other. They are all in the same temp conditions with no sun on them. Now if at 10am I start checking them I will find that the ones on the sunny side of my coach show 3 to 5 psi higher. So if I let air out of those they will be low by that much when running down the interstate. Get them set right the first time and leave them alone. Trust your TPMS. IMHO a TPMS is about the most important piece of safety equipment you can have on a larger RV.
Thanks Joe! Great info and advice. I have TPMS built into my F150 and have had cars with same for years. I don't get excited about minor changes in tire pressure, but know they'll alert me to serious issues. You've convinced me, I'm going to make this an early addition to my new RV.
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Old 06-12-2017, 03:14 PM   #19
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Originally Posted by Mike in AZ View Post
Thanks Joe! Great info and advice. I have TPMS built into my F150 and have had cars with same for years. I don't get excited about minor changes in tire pressure, but know they'll alert me to serious issues. You've convinced me, I'm going to make this an early addition to my new RV.
A well placed investment in my opinion...

Don't forget sensors for the toad/trailer if you intend to tow. While you may feel something going wrong with the RV tires - you likely will have no idea if something goes wrong on the toad... Will let you know of tire or braking issues (brakes overheating will drive up tire temp and alarm).
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Old 06-12-2017, 04:08 PM   #20
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Very good point gmc. A tire on my Trike trailer could blow and I could probably run it on the rim for 20 miles before seeing anything in my rear camera.

Not sure what folks towing 4 down set up. TPMS sensors generally need to be mounted on metal valve stems, plus would they even work right if there are generic OEM sensors present?
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