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Old 04-03-2021, 10:09 PM   #1
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Tire Pressure Question

The suggested maximum load tire pressure for my F350 is 80psi. My CC 5th wheel trailer tires maximum pressure is 110psi. The morning of each camping trip, before departure, I check all tires to make sure they are filled to maximum load pressure as stated above. I use a TST 507 TPMS on all my tires. Now here’s my question....which gauge do I use to set the tire pressure?

I use a Accutire MS-4021B Digital Tire Pressure Gauge (Amazon) to check the pressure. However, the TPMS will show 110psi only if the Accutire gauge reads 111-112psi. Should I fill the tires to match the TPMS or the Accutire? I’ve been trying to always have pressures match TPMS knowing the Accutire gauge reads a little higher. Is it okay to be within +/- 2psi on actual pressure? Should I even be concerned with this small difference? I don’t think there is a way to calibrate the TST 507.

What is everyone else doing to set tire pressure when using a TPMS?

Thanks in advance for the feedback.
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Old 04-03-2021, 11:10 PM   #2
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1 to two psi differential is not a problem .pick one gage and go with that.
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Old 04-04-2021, 07:10 AM   #3
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Find and use a pressure guage that you trust, fill the tires to whatever pressure you want and then use the pressures the TPMS displays as a reference. It doesn't matter if they match.

As long as you know you put the correct amount in with a known good guage, you are good. If you can't remember the differential between the guage and what reads on the monitor, maybe a little chart would help you.

My TST is off a few pounds too. And not only are the displays on the monitor a few PSI off from the guage, they are a few PSI off from each other but again, I don't care, it is just a reference.

I also pretty much quit using the manual guage before every trip. I'll fire up the TPMS as we are getting ready and if all the tires display what they normally do, no need to manually guage them.
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Old 04-04-2021, 08:12 AM   #4
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The suggested maximum load tire pressure for my F350 is 80psi.
Is this the pressure in the placard in the truck or the maximum sidewall pressure listed on the tires? Truck tires should use the placard pressure although up to the sidewall pressure won't hurt but won't increase cargo capacity; trailer tires should use the maximum sidewall pressure, there's never any reason to use less as they're just tagging along.

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Old 04-04-2021, 08:34 AM   #5
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Originally Posted by Chuck_S View Post
Is this the pressure in the placard in the truck or the maximum sidewall pressure listed on the tires? Truck tires should use the placard pressure although up to the sidewall pressure won't hurt but won't increase cargo capacity; trailer tires should use the maximum sidewall pressure, there's never any reason to use less as they're just tagging along.

-- Chuck
Placard pressure for a truck is good with a nearly empty truck. However for max weight performance of the tire the sidewall pressure needs to be used.
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Old 04-04-2021, 08:38 AM   #6
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Read the placard. That tire pressure will support the maximum allowable load the truck can take. Any more pressure does not increase axle weight rating or maximum load.

Truck tire can certainly run at maximum tire sidewall pressure but you really don't gain any capacity.

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Old 04-04-2021, 10:14 AM   #7
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Originally Posted by Cabinfever97 View Post
Placard pressure for a truck is good with a nearly empty truck. However for max weight performance of the tire the sidewall pressure needs to be used.
Wrong and then right....

Placard pressure on the pillar post or door jam is for the MAXIMUM LOAD the truck can carry, not empty or anywhere in between.

Maximum weight performance of the TIRE is indeed governed by the maximum pressure on the sidewall... but... if you put higher rated tires on the truck and then jack up the pressures to the maximum sidewall pressure, it DOES NOT increase the carrying capacity of the truck just as running maximum sidewall pressure on the factory tires will not either if the placard pressure is the lower of the two.
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Old 04-06-2021, 09:16 AM   #8
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I am the poster child for being meticulous and obsessed with tire pressures. I too use a TPMS on my truck and 5er and I'll work on it for an hour to get the pressures spot on.

I use 2 manual gauges and what I've found with both, the higher the PSI, the greater the deltas. So on one gauge to hit 110 on the TPMS, the manual gauge has to read 112. On the truck tires, to hit 65, it's pretty close (maybe 66 psi) on the manual gauge.

Bottom line though, I use the TPMS as the master source. After a cold soak, I expect the RV tires to be reading 110 all around, 70 on the front of the truck and 65 for the dual rears.

On the truck, it also has a built in TPMS and it jives with the external (valve stem mounted, TPMS. Hence....I trust the TPMS. My choice for TPMS is PressurePro.
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Old 04-06-2021, 09:51 AM   #9
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Quote:
Originally Posted by Chuck_S View Post
Is this the pressure in the placard in the truck or the maximum sidewall pressure listed on the tires? Truck tires should use the placard pressure although up to the sidewall pressure won't hurt but won't increase cargo capacity; trailer tires should use the maximum sidewall pressure, there's never any reason to use less as they're just tagging along.

-- Chuck
Goodyear tire company seems to disagree:
https://www.goodyearrvtires.com/tire...n-loading.aspx

Goodyear recommends inflating RV tires to the inflation pressure found in published load and inflation charts.

As an example:
https://www.maxxis.com/trailer/trail...nflation-chart

The simple answer is that you should inflate your trailer tires to the pressure indicated on the label provided by the trailer manufacturer as long as you have the same size tire installed, even if you moved up in load rating on the tires. Just because you move up in load range on the tire does not mean that you have increased the GVWR of the trailer itself.
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Old 04-07-2021, 02:37 PM   #10
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I guess there are different parts of the Goodyear document indicating differnt things. Also on the goodyear site:

" Unless trying to resolve poor ride quality problems with an RV trailer, it is recommended that trailer tires be inflated to the pressure indicated on the sidewall of the tire. Trailer tires experience significant lateral (side-to-side) loads due to vehicle sway from uneven roads or passing vehicles. Using the inflation pressure engraved on the sidewall will provide optimum load carrying capacity and minimize heat build-up."

My take is that you inflate Goodyear tires up to the max on the sidewall, as long as your rims can handle the pressure and the inflation pressure is equal to or greater than that indicated on the placecard of the trailer.

Perhaps other manufacturers have different guidelines.
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