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Old 03-27-2010, 08:38 PM   #1
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1977 24' Argosy 24
St. Augustine , Florida
Join Date: Jun 2009
Posts: 43
Question Tire pressure specs

My 77 Argosy has a placard on the chassis that calls for 70psi in the front tires and 55psi in the rear. I just recently got new tires and the tire shop guy said all the tires needed the presure called for on the tire and that less pressure was for comfort. The specs on my chassis are 33 years old! Are there any reasons other than comfort to keep the pressure in the rear tires less than the tires themselves call for?

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Old 03-27-2010, 10:38 PM   #2
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1987 29' Sovereign
Sparta , Tennessee
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I can think of a few but, to me none are really valid.

Your trailer may not have all of the heavy things centered over the axles like frig, kitchen cabinets, storage tanks, etc? They may have thought pulling with a wagon or car might put more weight on the front tires because the nose is down?

I agree with your tire guy. The number on the sidewall was not arrived at in a careless, flippent way. That sidewall inflation number will support the tire to match the contour the engineers want the tire to run at. Tread flat on the road, beads pushed firmly against the rim, sidewall flexing but, not deformed, etc. The manuf's do have on their web sites inflation at load charts so that you can work backwards and lower your pressure to obtain a softer ride. If your trailer is light relative to the max gvwr of the axles and tires, you can reduce inflation.

I run a load range D tire which is 65psi & 2540 lbs max loading. I actually inflate to 67 psi cold and lose about 1-2 lbs per month. I stayed in Newfoundland for the summer and since it was cool, didn't have to add air even though I had slipped to about 62psi.

I would make sure the trailer is level when towing, inflate to sidewall psi (unless your argosy is a shorter one and you have a lot of reserve load capacity) and ignore what the plate on the trailer says.

Just my $.02

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Old 03-27-2010, 10:39 PM   #3
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1982 28' Airstream 280
Port Angeles , Washington
Join Date: Aug 2008
Posts: 1,406
Your tire shop guy is wrong. The pressure on the tire is the max pressure allowed and is required to carry the max load indicated on the tire. The pressures indicated on your placard are based on the actual weight of your coach.

Weigh your coach at each tire and go to your tire manufactures web site and you will find a chart that specifies the pressure required to carry various loads up to the max. You will find you coach placard is pretty close. Any higher pressure will create a harsher ride.

Another method is to drive the vehicle at highway speeds for several miles to make sure the tires are totally heat soaked to normal operating temp. Pull over and immediately check the thread temperature with an infrared thermometer. Check the thread at each edge and the center. You want an equal temp across the thread. If it is warmer in the center of the thread, decrease pressure. If the edge of the thread is warmer, increase pressure.

Cheers, Dan
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Old 03-28-2010, 09:38 AM   #4
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1977 24' Argosy 24
St. Augustine , Florida
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Oh well. So much for a definitive consensus.
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Old 03-28-2010, 07:09 PM   #5
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1974 20' Argosy 20
Richmond , Kentucky
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Dan is absolutely correct. The air in your tires should match what the weight is on each corner of your motorhome.

The tires we run on our 310 are rated for something like 90 to 100 psi. When we first got it that's what the previous owner had in the tires because that's what the tire salesman told him to do. The ride was horrible. I changed the air pressures to match what was in the owners manual and the ride was unbelievably different.

The Chevy manual for our 1974 Argosy chassis lists weights allowed on tires based on the pressures. For example on a front tire (single tire) the 8.00 x 19.5 tubeless tire Load Range D ratings are:

30 psi = 1860 lbs
35 psi = 2030 lbs
40 psi = 2190 lbs
45 psi = 2350 lbs
50 psi = 2500 lbs
55 psi = 2650 lbs
60 psi = 2780 lbs

You need to weigh each front wheel corner weight and pressurize it to match the list above. For example if your left front wheel corner weight was 2500 lbs you would pressurize the tire to 50 psi.

Air forums # 1674
1974 20' Argosy Motor Home
1974 31' Excella trailer (parting out, as of 4/1/2015 I have wheels, brake drums, windows & holding tanks left to sell)
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