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Old 05-24-2021, 11:39 AM   #1
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Tire Pressure

I have a Forest River Georgetown 34' on a Ford Chassis. It is very light for a class A. A well-respected local RV repair shop weighed the wheels and advised me to run 70 PSI fronts and 75 PSI in the rear duallys. They pulled the pressures off the appropriate Toyo charts. My Mobile tire guy, also well-respected, says that is way too low, will ruin my tires and get bad mileage and I should be running close to 100 PSI. Drove the rig on a short trip (90 Mile) on a very windy day recently running the low pressure and was not happy being pushed all over the road. What would you recommend?
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Old 05-24-2021, 01:13 PM   #2
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Did you look to see?

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Originally Posted by floncto View Post
What would you recommend?
What year is your Forest River Georgetown 34' on a Ford Chassis?

What is the tire pressure specified by your manufacturer?

You should have a plate inside (near the drivers seat?), that tells you the tire size and pressure for your vehicle.
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Old 05-24-2021, 01:25 PM   #3
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Tire air pressures, age long debate.

I'm with your tire guy. Use the actual weight and load to psi table. But I like to add a buffer and add 10 to 15 extra psi. You can set up a tire for a blowout being under presure, but outside of some tire ware in the center treads no harm for being over pressured.
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Old 05-24-2021, 01:49 PM   #4
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I'll take the scaled weight and tire inflation tables over some guys off-the-cuff opinion anytime. Not all motorhomes need 100 psi - far from it!


The psi recommended by the coach builder is a good sanity test. It will provide enough inflation for a fully loaded (each axle at max weight) coach. If its less than 100 psi, there's your answer. And odds are you are running at less than max load.

Lower tire pressure doesn't cause you to get "pushed around" on windy days. If anything, just the opposite (softer tires tend to give increased traction). Excessively soft tires may feel mushy in turns, though.


Many Georgetowns are built on the Ford 20,500 lb chassis and have a max rear axle weight of 13,500. That's not a lot of weight. Tell us what tire size you have and we can do some actual analysis (not guesswork).
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Old 05-24-2021, 10:39 PM   #5
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My F53 is on a 24K chassis and per my weight and tire chart my proper tire psi should be 75 lbs., so I run at 80 lbs and that provides good handling and ride - or at least as good as it gets for my MH.
Thanks,
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Old 05-25-2021, 03:06 AM   #6
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Tire air pressures, age long debate.

I'm with your tire guy. Use the actual weight and load to psi table. But I like to add a buffer and add 10 to 15 extra psi. You can set up a tire for a blowout being under presure, but outside of some tire ware in the center treads no harm for being over pressured.
While I would rather be over than under on air pressure, over pressure penalties (in addition to wear issues) include a rougher ride and loss of traction, especially in the wet. I go with the tire manufacturer’s inflation table chart and CAT scale results.
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Old 05-26-2021, 03:49 PM   #7
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CAT scale results?

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... CAT scale results.
What are "CAT scale results"?
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Old 05-26-2021, 05:18 PM   #8
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What are "CAT scale results"?
CAT Scale Company provides the professional truck driver a reliable, accurate, and certified weight through the cooperative relationship with our truckstop partners. They will guarantee the highest quality at a fair price.
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Old 05-26-2021, 07:05 PM   #9
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I never did see your tire size.

Nearly all large truck tire (22.5") mfgrs. say to never run less than 80PSI.
Read what Bridgestone/Firestone has to say about RV tire inflation: https://www.bridgestoneamericas.com/...tires/rv-tires
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Old 05-26-2021, 11:22 PM   #10
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You'll never go wrong sticking to the RV manufacturer's placard, assuming you are still running the size tire that was on the vehicle when it left the factory. That will cover you up to the maximum GVWR of the vehicle. Chances are though that you're not going down the road at the maximum GVWR and can improve the ride somewhat by weighing your vehicle and using the tire manufacturer's load rating chart.

Of course, you'll then have to remember that if you add weight at any time (carrying extra passengers perhaps?) you might then have to adjust your pressures upward accordingly. That's one reason many of us use the tire load charts and then add 5 or ten psi buffer. In my case, that just about puts me back to what my motor home manufacturer recommended in the first place.
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Old 05-27-2021, 12:09 AM   #11
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What are "CAT scale results"?
In the App Store search Weigh My Truck. You’ll find the CAT scales app. Register. Find a truck stop with the CAT scale sign. Best time to weigh the RV is just after you fill up and are leaving on a trip. Follow the instructions on the app, pay about $12.50 and a minute later you have front, rear, axle and total weight on your phone. Easy, no need to get out and go in the store unless you want a hard copy of your weight.

With that info find your tire manufacture website to find your tire model and size. The chart will list how much pressure the tire needs for the weight it’s carrying.

Now you know the correct pressure to use.
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Old 05-27-2021, 01:18 AM   #12
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I have a F-53 chassis, 20,500. I also am running Toyos and I have their tire chart. My tire size is 19.5, 70, and for the life of me I can't remember the other number, but, according to the Toyo chart all the tires that size except the 225/70R19.5 say a minimum of 80lbs, 70 on the 225.
I am pretty well maxed out when I loaded up and got 4 corner weights from our state scales. My rear weights on both sides was 6600 for a total of 13,200. Some leeway. Left front 3440 and right was 3120 for 6560. Some room there to work with. Total 19,760. I also got a axel weight from a truck stop. Front 6,220, rear, 13,280 for a total of 19,500. Fairly close to the state. I'm not sure they are certified. All that being said, I ran 85lbs in the front and 95lbs in the rear. The rig ran fine. I have recently bumped it up to 90 front 100 rear. I haven't gone down the road yet with those numbers but I'm sure it will be fine. When I read that someone recommended 70 lbs I had to jump in and say something. Even if 70 is ok, I would not ever run that low on these tires. Just my 2c worth.
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Old 05-27-2021, 01:55 AM   #13
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What are "CAT scale results"?
In addition to what has already been posted, the CAT scale has 3 zones or plates. You can position your rig to get weights on the front axel (steer), rear axels (drive & tag) and toad (trailer). The plates are marked and your co pilot may need to guide you to ensure you hit the marks until you are used to the scale’s landmarks.
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Old 05-27-2021, 06:57 AM   #14
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CAT scale "How to weigh", and video (link) ...

https://catscale.com/how-to-weigh/
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