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Old 04-25-2017, 11:05 AM   #1
BZP
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Question Tire pressure issue

Seeking advice concerning the best tire pressures for my motorhome. I have a 2004 Winnebago Journey that is built on an oversized Freightliner chassis. The chassis GVWR is 27,900# and my coach weighs in at 21,180# fully packed and filled with liquids. I have Goodyear G670RV tires (26575R22.5G). Winnebago says I should have 100 psi in the rear tires and 105 psi on the front tires. I checked the Goodyear website and found that the 100/105 psi recommended tire pressures would be right if my coach weighed 29,519#.

I believe the Winnebago recommended pressure is too high because it was selected to cover my GVWR rather than the actual weight of my coach. The Goodyear inflation / load charts say I should use only 75 psi.

What is the best pressure for my tires? I believe a reduced pressure will give me a smoother ride but I question how the reduced pressure will affect my steering and handling. I am also concerned about making such a significant change without advise from other experts.

Does anyone have experience and recommendations?
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Old 04-25-2017, 11:13 AM   #2
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Are you going by the weight of the coach on the label, or the "hey I'm fully loaded for a trip and stopped by scales on the way out" weight?
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Old 04-25-2017, 12:00 PM   #3
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The label on the placard is tire pressure for MAX (GVWR) weight. If your actual weights are less than max you can run lower tire pressures. Somewhere out there there should be a table for your GY tires that specifies pressure required for weight carried. You should use the table vs guessing and potentially running under pressure.
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Old 04-25-2017, 02:13 PM   #4
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Go to good year and get tire pressure chart to weight . And get your motor home on a scale. Just do it . You will thank me later . 100psi you will feel every ripple in the road and pound things apart. My rigs only 12,300 rated 65 psi ( all tires are different) my real weight is 11,950 lbs 70 mph mines like riding in car. Ok newer Tahoe lol
But it's worth time and effort. To get exact psi.

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Old 04-25-2017, 05:44 PM   #5
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I have the same chassis and Bridgestone tires of the same size. 95 psi in the steer tires and 90 psi in the duals (drive tires) works just fine for me. I've been across the truck weigh station scales several times and my normal traveling/in use weight is in the 23,000 gvw range.
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Old 04-25-2017, 06:11 PM   #6
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All tires are different mine are gs so it says 3649 lbs per tire at 100 psi or 2100- 2450lbs at 65-70 p
si. Later I will dig up my chart.
If there duals ratings a bit lower.
It's a big deal.

I just figured out how to edit post in tap talk I have alot of posts to fix now lol

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Old 04-26-2017, 05:12 AM   #7
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Check the tire size on the Winnebago placards by the drivers seat. Note that the tires on it are 255/80R22.5 which is a Mitchlin tire. You have Goodyear 275/75R22.5 a larger heavier tire which requires less pressure for your weight.

My coach weight just under 27,000 and Goodyear recommends 85psi and I use 90psi so if it's a little cooler where I am I still at least 85psi.
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Old 04-26-2017, 08:03 AM   #8
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If you can weigh the coach fully loaded by each axle.

Set pressures by the Goodyear chart based on the heaviest weight for the front and the rear. In other words you front pressures should be set based on the heaviest weight of the fronts and the rears set based on the heaviest weight of the rears.

I also recommend a TPMS for keeping an eye on pressures and temperatures

Hope that helps.
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Old 04-26-2017, 08:46 AM   #9
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Generally correcty answers.

Proper tire inflation is based on the expected or known load on a tire. Winne can only guess on how much stuff you carry. Their inflation was based on the max load rating of the axles.

With your RV loaded to its heaviest (full fuel, clothes, water, food, tools and even your traveling bowling ball collection you need to get on a truck scale.

Ideally you need to get the "4 corner" weights as very few axles are balanced 50/50 side to side. You can learn more on how to calculate and where to find scales on this web site. Ya it's primarily 5th wheel trailer but they cover MH too.

Until you get the 4 corner weights at least get individual axle loads which you can get at any truck scale such as CATscale.

With just the axle loads calculate 53% of the axle as we assume a little unbalance. The 53% figure is used with Load & Inflation tables to learn the MINIMUM cold inflation pressure.

I recommend you run 110% of that minimum inflation as your Cold Inflation Pressure

I also strongly recommend you get and use a TPMS to decrease the chance of a sidewall blowout.
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Old 04-27-2017, 07:02 AM   #10
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Thanks

Thanks everyone for the valuable responses. I did weigh my rig on he CAT scales (fully loaded) and checked the Goodyear Tire Load/Inflation charts. Based on the load in my front and rear axles, the chart says a I can drop my pressure to 75 psi.

I will weigh my rig again and get individual wheel weights. I will then drop my pressures to 10 psi above the Goodyear chart pressures and do some test driving before heading off on a long trip.

One further question, does anyone know how the reduced pressures will effect my steering and handling? I expect a softer ride but wonder about handling on turns and straight line tracking.

Thanks Again for all the good I put.
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Old 04-27-2017, 11:14 AM   #11
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YMMV, but lowering the pressure on mine to what my actual weights required improved both the handling and ride.
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Old 04-27-2017, 01:20 PM   #12
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Quote:
Originally Posted by 4x4van View Post
YMMV, but lowering the pressure on mine to what my actual weights required improved both the handling and ride.
It's a big deal . On a motorhome. It's difference of riding like a hay wagon. To a car ride. Beside to much air in the tires really rattles the dishes. To little of air means heat in tire.

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Old 04-27-2017, 01:29 PM   #13
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Years ago my dad always had tires he had to put more a air to make weight rating. But in turn every line in the road. Bang bang bang . lol
There still dishes around showing wear marks lol. Years ago tires were not as good and RV tires we're non existent. 80s guys were just using tires like on delivery trucks. And there ratings were all screwy. Lot of air. Ride.. what's that lol and locktight on suspension bolts lol.

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Old 04-27-2017, 09:11 PM   #14
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I suggest you read this entire Goodyear RV tire inflation and loading webpage.
The paragraph, IMPORTANT, and the 1st and 2nd paragraph of TIRE LOADING, are not anyone's opinion, they are factual information from Goodyear. Your particular situation is different due to your non-OEM tire size.
I know I'm in a minority here about tire pressures, but backed up by Goodyear and Michelin websites.
Some asked why do mfgrs publish load/inflation charts if they also say to never run less than federal tire placard pressures. I don't know why tire mfgrs do so, but it's there in print.
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Old 04-27-2017, 10:49 PM   #15
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Quote:
Originally Posted by Ray,IN View Post
I suggest you read this entire Goodyear RV tire inflation and loading webpage.
The paragraph, IMPORTANT, and the 1st and 2nd paragraph of TIRE LOADING, are not anyone's opinion, they are factual information from Goodyear. Your particular situation is different due to your non-OEM tire size.
I know I'm in a minority here about tire pressures, but backed up by Goodyear and Michelin websites.
Some asked why do mfgrs publish load/inflation charts if they also say to never run less than federal tire placard pressures. I don't know why tire mfgrs do so, but it's there in print.
And my interpretation of those paragraphs is different than yours. Reading the entire section makes it clear that they don't want you to run lower pressures than the actual vehicle weight requires (the actual weight, not the max weight) in a search for a smoother ride. Which is exactly why they publish load/inflation tables, and why they send so much time explaining how to weigh your rig.

You have admonished me for picking and choosing parts of publications to determine a meaning, but that's exactly what you are doing. You choose a few sentences out of an entire publication, and take them out of context to prove your point. But the entire publication, taken as a whole, clarifies exactly what their recommendations are; which is to weigh the rig and set the tire pressures according to those actual weights. But this is a dead horse lately, so...
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Old 04-28-2017, 07:22 AM   #16
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Thanks again for all the input. It was very helpful to get everyone's perspective.

Happy Driving!
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Old 04-28-2017, 09:49 AM   #17
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Quote:
Originally Posted by BZP View Post
Thanks everyone for the valuable responses. I did weigh my rig on he CAT scales (fully loaded) and checked the Goodyear Tire Load/Inflation charts. Based on the load in my front and rear axles, the chart says a I can drop my pressure to 75 psi.

I will weigh my rig again and get individual wheel weights. I will then drop my pressures to 10 psi above the Goodyear chart pressures and do some test driving before heading off on a long trip.

One further question, does anyone know how the reduced pressures will effect my steering and handling? I expect a softer ride but wonder about handling on turns and straight line tracking.

Thanks Again for all the good I put.
Until you get individual axle end weights you can use 53% of the axle load as a good starting point for the MINIMUM inflation needed.

If you drop off the bottom of the chart DO NOT go lower than the lowest chart number.

Remember ALWAYS set all the tires on any one axle to the same pressure (pressure for heaviest measured or estimated load) DO NOT set pressures on individual tires based on individual load measurements or calculations.

I agree and support adding 10% or 10 psi to the MINIMUM pressure needed for your morning CIP set point.

Pressure based on actual loading +10% will deliver a good balance of ride & steering response.
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Old 04-28-2017, 12:55 PM   #18
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I was having trouble finding the Load and Inflation tables for the new Toyo M154's on our Adventurer. Found lots of Toyo L/I tables for passenger car/trucks but nothing for the heavier duty vehicles.

I sent Toyo an email yesterday with my axle weights front and rear and they responded immediately with their recommended inflation pressures for my loads.

Toyo M154 245/75R22.5

Front axle Single
8,500 = 4,250 lbs. per tire = 95 psi (4,300)

Rear axle - Dual
14,900 = 3,725 lbs. per tire = 90 psi (3,765)

On page 73 of the link below you can find the Load and Inflation tables for Toyo tires. I know that doesn't apply to the OP's tires but it may be helpful for someone looking for this info on Toyo tires.

http://www.atoztire.com/includes/ima...um%20truck.pdf
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Old 04-28-2017, 01:16 PM   #19
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Originally Posted by Ray,IN View Post
I know I'm in a minority here about tire pressures, but backed up by Goodyear and Michelin websites.
Toyo as well!
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Old 04-28-2017, 01:30 PM   #20
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Here's a psi to weight chart example only. I noticed rigs over 20,000lb psi gets super high.

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