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Old 10-10-2018, 06:15 PM   #1
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Trailer Tires -- How much is too much PSI

Just finished a trip from Dallas Tx to Durango CO. Fun trip!!

Before leaving I set the 4 tire to 65psi +- a pound. During the trip at several gas stops I checked the tires. Found they running at about 74psi. I do expect them to heat up but that seemed a little excessive for pressure. So I backed them down to 68psi. When cooled they were back at 63/62psi.

So is 74psi too much? Not sure what the norm for running tires are...
These are the tires that came with the camper (china bombs I guess) but we've got over 7000 miles on them with no issues.

I do plan on getting one of those "Tire Minder" kits, just need one I don't have to squint to read the numbers.

Thanks All, for your comments and replies!!
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Old 10-10-2018, 06:49 PM   #2
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The maximum pressure is embossed on the tire side walls. That pressure applies when cold. Checking the pressure when they are hot is not recommended. I don't know of any "Hot" temperature equivalents.
Tires will fail if the pressure falls for any reason including letting air out because you think the pressure is too high. The more air you vent, the hotter they will run.
Tires also fail because they are over-loaded. Tires flex more when they are loaded more. Look at the angle the tire makes where it meets the road. The heavier the load, the sharper the angle. The sharper the angle the quicker the imbedded belt fatigues and breaks. No amount of temperature or pressure monitoring will stop it especially with steel belted radials.
TT manufactures usually use undercarriages, wheels, and tires that barley meet specified loads. Some TT manufacturers tires don't meet gross weight capacity. Some tire manufactures don't bother to test their tires or if they do don't care if they are marginal or insufficient.
Don't let air out if you maintained pressure regularly. Add air if pressure drops while driving. Let tires cool to ambient temperature before testing and adding air.
Things you can do to reduce likely hood of tire failure.
1 Check and maintain pressure regularly when tires are cold.
2 Get nitrogen fill in your tires. This reduces oxygen and water vapor in side the tire. Tires pressures will be less sensitive to ambient temperature changes like driving from a southern Arizona valley to a northern Arizona mountain peak.
3 Replace all the tires with higher capacity good brand of tires. If necessary and the trailer has room for them get bigger or wider rims to get increased capacity.
4 Beef up your undercarriage if others are reporting issues. The tires depend on stable well aligned support.
5 … does anyone else have more to add? ...
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Old 10-10-2018, 08:34 PM   #3
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Originally Posted by persistent View Post
5 … does anyone else have more to add? ...
Nitrogen is a waste of money imo. I've added air 3-4 times in the first year of having them done, theyre at least 50% compressed air right now. I would never pay for nitrogen, the tire shop did it without asking.

To the op, I would bet your tires are max inflated at 50psi cold, unless you have a Voltage with the bigger tires (it's helpful if you put your camper info in your signature line). Inflate to 50 psi cold before you leave for a trip, and don't check them again until you leave for your next trip.
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Old 10-11-2018, 02:43 AM   #4
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I think I ran into your twin a couple of years ago. He was checking his air pressure at a rest stop and was letting air out to keep the pressure at 80 PSI. I really had a hard time not busting out laughing.
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Old 10-11-2018, 11:39 AM   #5
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Nitrogen is a waste of money imo. I've added air 3-4 times in the first year of having them done, theyre at least 50% compressed air right now. I would never pay for nitrogen, the tire shop did it without asking.

To the op, I would bet your tires are max inflated at 50psi cold, unless you have a Voltage with the bigger tires (it's helpful if you put your camper info in your signature line). Inflate to 50 psi cold before you leave for a trip, and don't check them again until you leave for your next trip.
I run Nitrogen in my truck tires, the place down the street tops them off for free. As far as the RV is concerned, I changed the china bombs for Goodyear's and put just plain air. no problem ! The NITROGEN stuff would not stay in and kept needing to be topped off. practically impossible to find Nitrogen places where you can get your RV in and out.
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Old 10-11-2018, 09:07 PM   #6
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I am not familiar with your trailer but it should have a recommended cold pressure sticker. That pressure provides for max carrying weight. The pressure stamped on the sidewall will likely be different and probably higher. I would go with the trailer recommendation and not the tire. The only exception is if you are way under your max weight you could go a little lower for a softer ride but since you donít travel in the trailer I donít think it is necessary to lower.

Tires are designed to have the pressures increase when hot so ignore high pressures when towing. Obviously, lower pressures are a problem and signs of a leak.
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Old 10-13-2018, 02:47 AM   #7
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"The only exception is if you are way under your max weight you could go a little lower for a softer ride but since you don’t travel in the trailer I don’t think it is necessary to lower. "


Tire manufacturers publish weight and speed tables. Use the tables for your speed and weight. ST (Special Trailer) tires have a maximum speed rating o 65 MPH. The embossed cold pressure on the tire side wall IS the maximum to prevent blow out and early failure. Going to faster than the Mfg'ers pressure and speed tables is a recipe for early failure.
Lightly loaded tire survive in spite of excessive speed and pressure, but there are no guarantees.
Remember the abuse you heap on your tires today may not show up until tomorrow.
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Old 10-13-2018, 02:57 AM   #8
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Originally Posted by persistent View Post
"The only exception is if you are way under your max weight you could go a little lower for a softer ride but since you don’t travel in the trailer I don’t think it is necessary to lower. "


Tire manufacturers publish weight and speed tables. Use the tables for your speed and weight. ST (Special Trailer) tires have a maximum speed rating o 65 MPH. The embossed cold pressure on the tire side wall IS the maximum to prevent blow out and early failure. Going to faster than the Mfg'ers pressure and speed tables is a recipe for early failure.
Lightly loaded tire survive in spite of excessive speed and pressure, but there are no guarantees.
Remember the abuse you heap on your tires today may not show up until tomorrow.
Which is precisely why I don't have ST tires on my trailer. I don't worry about the pressures, temps, speeds, or any of that stuff. If applicable, truck tires are the only way to go on a trailer.
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Old 10-17-2018, 08:53 PM   #9
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Quote:
Originally Posted by Texas Camper View Post
Just finished a trip from Dallas Tx to Durango CO. Fun trip!!

Before leaving I set the 4 tire to 65psi +- a pound. During the trip at several gas stops I checked the tires. Found they running at about 74psi. I do expect them to heat up but that seemed a little excessive for pressure. So I backed them down to 68psi. When cooled they were back at 63/62psi.

So is 74psi too much? Not sure what the norm for running tires are...
These are the tires that came with the camper (china bombs I guess) but we've got over 7000 miles on them with no issues.

I do plan on getting one of those "Tire Minder" kits, just need one I don't have to squint to read the numbers.

Thanks All, for your comments and replies!!
The cold tire inflation is what the tire pressure should be resting. Extra inflation from friction heat (rolling) is built into the tire specs and is normal .
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Old 10-17-2018, 09:31 PM   #10
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Originally Posted by persistent View Post
The maximum pressure is embossed on the tire side walls. (That pressure is the max pressure when initially mounting and is NOT the max operating pressure. I suggest you read the actual "Safety Warning" words.)That pressure applies when cold. Checking the pressure when they are hot is not recommended. I don't know of any "Hot" temperature equivalents.
Tires will fail if the pressure falls for any reason including letting air out because you think the pressure is too high. The more air you vent, the hotter they will run.
Tires also fail because they are over-loaded. Tires flex more when they are loaded more. Look at the angle the tire makes where it meets the road. The heavier the load, the sharper the angle. The sharper the angle the quicker the imbedded belt fatigues and breaks. No amount of temperature or pressure monitoring will stop it especially with steel belted radials. While the angle between the road and tire is of some concern it is the Interply Shear that causes belt separations in radial tires. You can learn more HERE
TT manufactures usually use undercarriages, wheels, and tires that barley meet specified loads. Some TT manufacturers tires don't meet gross weight capacity.( If that is true then a complaint with documentation to NHTSA would start a recall) Some tire manufactures don't bother to test their tires or if they do don't care if they are marginal or insufficient. The tests are only a minimum level that all tires are supposed to be able to meet. If you have data then file a complaint with NHTSA and there will be a recall
Don't let air out if you maintained pressure regularly. Add air if pressure drops while driving. Let tires cool to ambient temperature before testing and adding air. (2 hours after running or after being in direct sunlight)
Things you can do to reduce likely hood of tire failure.
1 Check and maintain pressure regularly when tires are cold. YES
2 Get nitrogen fill in your tires. This reduces oxygen and water vapor in side the tire. Tires pressures will be less sensitive to ambient temperature changes like driving from a southern Arizona valley to a northern Arizona mountain peak. IMO N2 is only worth it if free and convenient.
3 Replace all the tires with higher capacity good brand of tires. If necessary and the trailer has room for them get bigger or wider rims to get increased capacity.
4 Beef up your undercarriage if others are reporting issues. The tires depend on stable well aligned support.
5 Ö does anyone else have more to add? ...

As an actual Tire Design Engineer (not a salesman) and RV owner I added my comments in RED above. You can learn more facts by reading or subscribing to my RV Tire blog. Address below.
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