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Old 12-05-2022, 11:26 AM   #1
mikeburns
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Default tire pressures

I'm a bit confused regarding tire pressures on my 2003 model 5210b. The sticker inside of the cabinet appears to say 55 PSI on all 6 tires. But the manual, and chassis manuals don't even mention a pressure. When I searched online, most people said 65 in the fronts, and 80 in the rear. I'm getting ready to take our first trip in this RV and would like to start out with the proper pressure.
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Old 12-05-2022, 08:20 PM   #2
sdw215
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I'm a bit confused regarding tire pressures on my 2003 model 5210b. The sticker inside of the cabinet appears to say 55 PSI on all 6 tires. But the manual, and chassis manuals don't even mention a pressure. When I searched online, most people said 65 in the fronts, and 80 in the rear. I'm getting ready to take our first trip in this RV and would like to start out with the proper pressure.
Hey Mike, go by the pressure listed on the tires themselves. The max cold pressure will be listed. This is a good starting point depending on the total weight you’ll be hauling.

For example, on my 2019 VC 19ERD the label says 75psi for the original tires that came on it for the GVWR of ~4384lbs. The ones on it currently list 65psi. So depending on the weight when towing it 65psi is the max cold pressure. When towing less I can lower it to 60psi to prevent the trailer from getting hammered on uneven roads from max tire pressure. Make sense?

So as tires have different load ratings your tires (assuming they’re all the same) will have their max cold psi listed as well as their load rating. Mine are 205/75 R14D. R means radial. D is the load rating. Hope this helps.
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Old 12-05-2022, 10:21 PM   #3
NavyLCDR
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Be aware that there is a huge difference between tires on a trailer and tires on a motorhome. The previous post by sdw215 is regarding trailer tires, not tires on your motorhome.
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Old 12-06-2022, 11:13 AM   #4
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Be aware that there is a huge difference between tires on a trailer and tires on a motorhome. The previous post by sdw215 is regarding trailer tires, not tires on your motorhome.
I thought I made that abundantly clear. In any case you should never exceed the psi nor load rating stamped on a tire. It typically ends in disaster.
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Old 12-06-2022, 08:36 PM   #5
NavyLCDR
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Assuming you have the same load range and size tires on the vehicle that it came from the factory with, the starting point for vehicle tires is the pressure listed on the tire certification label, not the max on the sidewall of the tire. This is because a vehicle tire has two primary functions, to provide contact and traction with the road as well as supporting the weight of the vehicle. In order to achieve the proper amount of road contact between the tire tread and the road, the pressure must be reduced below maximum on the tire if the tire is not supporting the maximum weight.

If you want to run your trailer tires at maximum pressure on the sidewall (cold inflation, not running), then you simply increasing load reserve. Tread contact with the road is not as big a deal as with vehicle tires because the main singular purpose of trailer tires is to support the load, not traction. The trailer does get a bumpier ride, though.
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Old 12-08-2022, 04:44 AM   #6
Leisure Time Larry
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Originally Posted by mikeburns View Post
I'm a bit confused regarding tire pressures on my 2003 model 5210b. The sticker inside of the cabinet appears to say 55 PSI on all 6 tires. But the manual, and chassis manuals don't even mention a pressure. When I searched online, most people said 65 in the fronts, and 80 in the rear. I'm getting ready to take our first trip in this RV and would like to start out with the proper pressure.
Hi Mike, the quick answer is to go by what that coach sticker says. They built it!

The subject is more complicated when looking into all that goes into it like tire construction, tire ratings, handling, weight, balance, load distribution, age, etc.

I have a '05 model 5211B, so very similar to yours. I have done all of the things you are supposed to do to find the "right" tire pressure number. I've weighed it, looked at the load distribution, added a 5% safety factor for each tire, referenced the tire inflation charts, and guess what? It all led me to the same PSI as what my coach sticker says.

I do recommend you look at a couple of things on your tires before your first trip though...

1) What is the max cold tire pressure listed on your tires? Mine came with Load Range D tires with a max of 65 PSI cold. I'm guessing yours did too. If you have D tires, then you cannot put that recommended 80 PSI in those! Load Range E tires are often installed as replacement tires, and those typically have a max of 80 PSI. So, it's important to know what tires you have and how much pressure they can aired up to.

2) What is the date code on your tires? This is usually a 4 digit number inside of an oval somewhere on the sidewall of a tire. This represents the tire's birthday. The first two digits are the week and the final two digits are the year the tire was made. An example may be: 0422 A tire with this code would have been made during the 4th week of 2022 (so end of January 2022). Tires are recommended to be replaced about every 6 years, and the older they are after that, the more dangerous they are considered. That stinks for us RV owners that may not put very many miles on. Our tires usually "age out" quicker than get "worn out". Be aware of your situation and act accordingly.

Best of luck with your new rig. Here's to many miles and smiles!
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Old 12-08-2022, 04:55 PM   #7
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As several have said, the max psi rating on the tire is for the max load rating of the tire. As said, the true vehicle inflation is never more than that, or they have specified the wrong tires for that application. It is usually less than the value on the tire. Vehicle tire pressure effects ride, handling, braking, fuel economy, & tire life so the mfg should consider all this in recommending a pressure. As an automotive development engineer, if done proplerly it is complex. The BT cruiser I had, had the door frame sticker, which came from Ford, and then 2 additional stickers on the exterior of the cab behind the drivers door. Both were higher pressures in the rear than the OEM sticker. Neither were date or referenced the other. So I concluded that there was change made after Gulfstream built the vehicle. Obviously Gulf stream is careless with the info, and Ford has no idea how the vehicle will be configured and the nor the weights or weight distribution, they are just delivering a cut a way Ford Van. The Ford sticker is just general info and not specific. My own experience was not to inflate to 80 psi when traveling as the ride impacts were horrible and I didn't want to jar the coach apart. I used 65 psi, but I did travel with minimum fresh water and mostly empty grey and black tanks, but full fuel tank. The former is all located at the very rear on my RV, so that is the worst configuration for load on the tires. Just passing on my vehicle experience, but if you want to optimized consider that you may be operating at minimum weight or near GVWR and there is not 1 best number for both. Just never run underinflated for the conditions you are operating
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Old 12-11-2022, 05:50 PM   #8
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Smile Proper Inflation of Tires

My question/response is for anyone to answer but also hoping 'hossross' will respond. I retired after 30 years of quality assurance for aircraft tires. I realize they are different from ground tires but I've never understood why people go by what the RV says instead of the tire.
We had a huge portion of our workforce in development and quality control to make the tires both consistent and to a certain standard. It seems to me that the best people to know what the tires is designed for is the tire manufacturer.
In the 1990s there was the Firestone incident in which Ford and Firestone agreed the tires should be run underinflated to make the ride comfortable,etc. But over 750 people died (I believe that's the correct number) from blowouts.

In the case of Mike Burns question, I wonder what the tires were made for? It's a 2003 RV so what if the first owner put tires on that aren't designed for a chassis exactly like his. What if they are cheap tires or have dry rot from age? It scares me to think that tires that might already be weakened could then be over or underinflated for comfort's sake. Underinflation, which was the problem with the Ford/Firestone issue puts more pressure on the tire's sidewall. Overinflation doesn't keep as much tire on the road.

I hope this didn't come across as arrogant or argumentative. I have often heard people say to go by the RV rather than the tire. This is just the first time I've asked why and I wanted to present my case. I specifically mentioned 'hossross' because he mentioned he was in automotive development and thought he might shed light from the automotive side of things.

Thanks for answers in advance.
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Old 12-11-2022, 07:15 PM   #9
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My question/response is for anyone to answer but also hoping 'hossross' will respond. I retired after 30 years of quality assurance for aircraft tires. I realize they are different from ground tires but I've never understood why people go by what the RV says instead of the tire.
For the same reason that aircraft tires are inflated according to the aircraft specifications rather than the tire spec. A tire made for aircraft use can be used on multiple aircraft and each aircraft will have its spec for tire inflation based upon aircraft weight and takeoff/landing speeds. In the case of Naval aviation, the tire inflation pressure is higher for aircraft carrier operations than it is ground operations.

The reason for varying vehicle inflation pressures is to ensure that there is proper tread contact with the road to maintain traction while also maintaining adequate cooling.

My wife's 2017 Grand Caravan calls for a inflation pressure of 36 PSI. My 2015 GMC Yukon calls for 35 PSI. My Toyota Prius calls for 33 Front, 32 Rear. All the tires for all three vehicle have 44 PSI max on their sidewalls. So would you recommend I just run all the tires at 44 PSI because that is what is on the side of the tire? If I ran them all at 44 PSI, I would lose traction (especially on wet pavement) as well as wearing the center of the tread more than the edges causing the tires to wear prematurely.

Very Respectfully,
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Old 12-12-2022, 12:14 AM   #10
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The 5210 is a (comparatively LIGHT) 21-ft+ BT Cruiser, and if DRIVER DOOR JAMB LABEL also says 55 on all tires, that is what I would go with. The paper labels inside cabinets have recalls where wrong INFO was put on them by coach MFR; never seen a recall by Ford/GM for metal DOOR JAMB LABEL.
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Old 12-12-2022, 10:13 PM   #11
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Tires do generate a lot of opinions, but its the fact we want. I think NavyLCDR gave you a simple & accurate answer on why a tire that is designed with specific characteristics including max load at a max pressure can be used on many different applications. Modern SUV's are "over tired" just to get the appearance. Remember when cars had skinny tires, and how much better they look with wider tires. The low side wall height is the same, it has a unique appearance and can generate much higher lateral force on those low CG (center of gravity) vehicles that can safely handle it. RVs are not those they have ridiculously high CGs,s On class C RVs rarely do you need the same tires on the front axle as the back axle(s), based on the maximum ACTUAL weight on the front is much less than can be loaded on the rear axle(s). If the manufacture wants to keep the same tires all around so you don't to have 2 size of spares or even no spares, the adding tires on the rear or duallys will double the max ALLOWED load on the rear axle(s). On a class C, the weak link is usually GVWRA, and not GVWR or GVWRF, because there is so much overhang and heavy things rearward of the rear axle. Water weights 7.48 pounds per gallon, Gasoline is 6 pounds per gallon. The fuel tank is normally between the front and rear axles, so the front supports some weight, but because the fuel tank is closer to the rear axle, it gets more and can be proportionally calculated from middle of tank to the distance of each axle. If the water and waste tanks are mounted rearward of the axle, all that weight is supported totally by the rear tires. So depending how big of tanks the RV mfg uses, how much "Cargo & people" are allowed by the RV Mfg, (usually their is an implied/assumed weight distribution of the cargo and people by where there is passenger and bed accommodations and where the kitchen ref and cabinets are as well as external storage. So since these are all design variables, the actual weight to be carried of each model will be different. Again the recommended tire pressure by the RV should consider Vehicle tire pressure effects ride, handling, braking, fuel economy, & tire life. So back to a Ford Van that Ford supplies as a cut away (which is really a partial build, not a cut away of the body as it was once done) Ford has to certify they are supplying a vehicle of certain capabilities. They set the GVWRating, GVWRFront, GVWRRear because the frame, axles including springs, tires, and power train have all been selected to deliver those capacities. Because the axles already exist and Ford can't do a custom axle for such low production volume often it is the parts that determine the GVW's. Because how much power needed to be a pleasant confident vehicle to drive is more subjective, the engines provided may or may not be "adequate" to each customer. Anyway bottom line on tires, they are selected for their load rating based on the GVW's, the tire company has designed that tire to a max pressure to carry that load. The ACTUAL weight carried by each tire is a function of all the content, weight, and weight distribution and hence the tire pressure can be different and typically will be when completed by the RV mfg.

If you want to understand more about the handling of an RV, read my post on what shocks, springs, and roll bars really do, I have not gotten a single question on it, I either made it too complex, or it conflicts with common beliefs that better shocks control vehicle roll, or can lift the body. Tires also play a roll in that also, as a tire side wall is a part of the "vehicle suspension rates".

The rule should be always use the RV tire pressure recommendations when the RV is fully loaded, Do not use the Vehicle sticker as it is not tailored to the RV application. Many have said inflation is to optimize the tire contact patch, that is also true in that the greatest patch area will provide the best traction and wear. What I gave you was design load based, Remember above I said I tailor the ACTUAL tire pressure to the roads and loads and speeds I drive. Looking at the tire wear, 1 uniformly across, 2 center mostly, or 3 edges mostly are long term indicators of how well you've matched an ideal tire pressure with the loads and load distribution for your roads, speeds

Does this answer your question(s)?
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Old 12-13-2022, 02:10 PM   #12
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I agree with all the automotive information that Navy LCDR provided. GM choose 35 psi to optimize fuel economy as the most significant parameter, because in real life handling would like a different tire pressure, than ride, than wear, than traction. So all other parameters are tuned to the 35 psi, Toyota choose a lower pressure and different pressure front to rear and fine tuned all other parameters to that number. Point is all could be using the exact same time (not in this case, but as an example of the tire is commodity and each users can specify a unique pressure for an application.
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Old 12-13-2022, 02:39 PM   #13
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Originally Posted by Just Cruisin View Post
My question/response is for anyone to answer but also hoping 'hossross' will respond. I retired after 30 years of quality assurance for aircraft tires. I realize they are different from ground tires but I've never understood why people go by what the RV says instead of the tire.
We had a huge portion of our workforce in development and quality control to make the tires both consistent and to a certain standard. It seems to me that the best people to know what the tires is designed for is the tire manufacturer.
In the 1990s there was the Firestone incident in which Ford and Firestone agreed the tires should be run underinflated to make the ride comfortable,etc. But over 750 people died (I believe that's the correct number) from blowouts.

In the case of Mike Burns question, I wonder what the tires were made for? It's a 2003 RV so what if the first owner put tires on that aren't designed for a chassis exactly like his. What if they are cheap tires or have dry rot from age? It scares me to think that tires that might already be weakened could then be over or underinflated for comfort's sake. Underinflation, which was the problem with the Ford/Firestone issue puts more pressure on the tire's sidewall. Overinflation doesn't keep as much tire on the road.

I hope this didn't come across as arrogant or argumentative. I have often heard people say to go by the RV rather than the tire. This is just the first time I've asked why and I wanted to present my case. I specifically mentioned 'hossross' because he mentioned he was in automotive development and thought he might shed light from the automotive side of things.

Thanks for answers in advance.
In most cases like all the RV applications, they don't buy enough tires to warrant the tire mfg to design a specific tire for the application so that is why you don't use the tire pressure on the side wall as the authority. Some vehicles sell enough that the tire mfg will provide a specific design tire but that number is probably over a million tires.

Now for the mystery part, Ford Explorer accidents. My short answer is Ford had better lawyers than Firestone. Ford had a handling stability problem in the design, they chose to minimized it by lowering air pressures to 26 psi on the rear tires, When tires loose pressure it goes lower from the starting point, so now some Explores had tire heating and deteriation problems. The rest is a bunch of cascading failures from there, read the wikipedia article for some more details. What I never saw an good engineering answer to was why did many of the vehicles that rolled over have a flat LR tire. in all cases the LR was lower pressure after the accident than the other 3 tires as I understand it. So why does 1 out of 4 tires consistently loose air more than the other 3 over thousnds of vehicles? The result was to trip the vehicle and killed a lot of passengers, Firestone went bankrupt
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Old 12-13-2022, 03:05 PM   #14
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I hope this will simplify things.
1. Download the tire pressure inflation chart for your brand of tire (I have Michelin).
2. Load the coach with your typical travelling weight.
3. Go to a truckstop ( I used TravelCenters of America), and have the coach weighed. I weighed mine while heading out on a trip so I didn't have to load it up specifically to weigh it.
4. Adjust pressures on each axle as per the chart.
By the way, I use 65 psi in the front (BT Cruiser 5270).
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Old 12-13-2022, 03:34 PM   #15
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can you add the link for your tires as an example. I looked and the Mitchellin web site does not let you search by make model. So I assume you need the tire size, model, and load range to use the chart you like. thanks
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Old 12-13-2022, 03:57 PM   #16
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One would assume that, as time goes by, manufacturers web sites would become more informative. Not in this case - I can't find the chart that I use from years back. And yes, the chart is organized by size, model and load range.
I'll poke around and post if I can find the chart someplace else.
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Old 12-13-2022, 04:39 PM   #17
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Thank you to all who answered the question. It has helped very much.
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Old 12-19-2022, 02:25 AM   #18
Henry111
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I demanded a TPMS for my auto to import from Canada to the US. The Kai dealer and utmost stores told me it could not be added after the request. You were wrong! As a result, my auto was imported without any problems. I paid for a shop to install it to produce a paper train, but indeed I could have done it myself! I'll also be buying another one to import my son's auto!
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Old 12-19-2022, 10:06 PM   #19
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Originally Posted by hossross View Post
I agree with all the automotive information that Navy LCDR provided. GM choose 35 psi to optimize fuel economy as the most significant parameter, because in real life handling would like a different tire pressure, than ride, than wear, than traction. So all other parameters are tuned to the 35 psi, Toyota choose a lower pressure and different pressure front to rear and fine tuned all other parameters to that number. Point is all could be using the exact same time (not in this case, but as an example of the tire is commodity and each users can specify a unique pressure for an application.
Repost of the below answer to correct the word TIRE which is now shown capitalized, The edit button was not available, I agree with all the automotive information that Navy LCDR provided. GM choose 35 psi to optimize fuel economy as the most significant parameter, because in real life handling would like a different tire pressure, than ride, than wear, than traction. So all other parameters are tuned to the 35 psi, Toyota choose a lower pressure and different pressure front to rear and fine tuned all other parameters to that number. Point is all could be using the exact same TIRE (not in this case, but as an example of the tire is commodity and each users can specify a unique pressure for an application.
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Old 01-17-2023, 09:17 AM   #20
JAYDEE10
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Originally Posted by ezdriver View Post
I hope this will simplify things.
1. Download the tire pressure inflation chart for your brand of tire (I have Michelin).
2. Load the coach with your typical travelling weight.
3. Go to a truckstop ( I used TravelCenters of America), and have the coach weighed. I weighed mine while heading out on a trip so I didn't have to load it up specifically to weigh it.
4. Adjust pressures on each axle as per the chart.
By the way, I use 65 psi in the front (BT Cruiser 5270).
Very helpful. Thank you for the email. Will follow the steps and let you know how it goes.
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