How to Determine the Right Air Pressure to Fill a Trailer Tire

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Question:

Hello, i just bought a pop up camper and ive been going crazy trying to find out how much air pressure i should fill the tires too, everybody tells me that i should fill them out to 35 psi but the tire says max 60 psi. the tire also says that its load rate is 1,360 lbs and according to my calculations that comes out to 2,720 lbs but the weight of the trailer without weight is 2200 lbs and i could add an extra 700 lbs, that comes out to 2900 lbs. that exceeds the both tires together? so i was thinking that i should buy a bigger tire, a whopping 14inch tire. i feel so lost. i just want to be able to feel safe pulling the trailer and not put my family in any danger weaving threw mountain grades. what would be the proper psi for the tire? and should that be with the weight of the trailer on the tire or with the tire off the ground or off the trailer ? should i put a bigger tire? size ST205/75R14, i wonder if they would fit?

asked by: Eli

1

Helpful Expert Reply:

I can end this debate for you real fast! Trailer tires, which will have an ST in front of the size, should always be inflated to the maximum psi indicated on the tire. Trailer tires usually do not have a recommended and maximum psi indication so I am curious if the tries on the camper are ST tires or regular passenger vehicle tires. On a regular trailer tire you would inflate it to the max psi indicated on the tire because trailer tires are built with a thicker sidewall to handle more vertical load.

If a trailer tire is under inflated, because of the thicker sidewall it will generate excessive heat and that is what leads to failure.

Check the camper frame and there should be a sticker or plate that lists what tire size should be on the trailer. It could also be in the owners literature. That is the size you will want to stick with.

Any given size tire can have different load ranges. For example an ST175/80-13 load range B will have a capacity of 1,100 pounds at 35 psi. But a load range D in the same size, # AM10210, is rated for 1,610 pounds at 65 psi. So you do not need a larger size, you just need a higher load range.

The wheel also has to be rated high enough. Tires and wheels are not always rated the same. There should be a sticker on the back of the steel or possibly stamped into the metal and indicates the wheel capacity and psi rating.

If you are not sure then the safe bet is to replace the tires and wheels. To do that I would need to know the bolt pattern of the wheel. I have linked a help article that shows how to measure for bolt pattern. I have also included a link to our informational article on trailer tires for you.

expert reply by: Michael H

1

Michael S.

9/4/2020

I have a 2018 Thor Windsport 34J. The sticker in the RV says to inflate tires to 90 PSI but the tires say 110 PSI. Which one is correct?

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Jon G.

9/5/2020

For trailer tires we always recommend going with what's printed on the sidewall of the tire. For a motorhome like what you have it would be better to treat that like a passenger vehicle and inflate the tires to the 90 psi that the sticker states (provided these are the exact same size and load range).

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Ryan K.

4/18/2021

@JonG Hello, I have a 2009 Jayco Jay Feather x213. It had load range C tires on it with a 50 PSI. It also says that on the trailer itself (Sticker with weight ratings, etc.). The trailer now has tires on it that are load range D saying "inflate to 65 PSI for max load" on the tires. We never fully load the trailer with gear. Do I keep the cold tire pressure at 65 PSI or at 50 PSI as it says on the trailer itself? Thank you.

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Jon G.

4/22/2021

@RyanK Great question! Since my post above we have actually been getting some different feedback from the manufacturers and they are a little more okay with PSI ratings being adjusted per load. What I would do in your situation is check with the tire manufacturer to see if they have a progression chart for different weight ratings and if they do then go by that. If they don't then I would just say to go by the PSI rating on the tire just to be safe.

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Dan

4/30/2024

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Allen B.

6/26/2024

Like many others with the same question regarding tire pressures for a travel trailer, you emphatically stated that the tires should be filled to the max cold pressure indicated on the tire. I have dual axles with Goodyear Endurance ST205/75R14 tires. Max cold pressure on the tire is 65 psi and the gross weight of my fully loaded travel trailer is 5,850 lbs, or 1,462 lbs per tire. Goodyear has a published load/pressure chart for the Endurance ST tires, and for my trailer weight, the published cold pressure is 40 PSI. I contacted Goodyear, giving them the specs above, and they said use the pressure chart, not the max 65 PSI. It makes sense, else why would they publish a load/pressure chart?

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Bud M.

6/26/2024

@AllenB The Goodyear is one exception to the rules of trailer tire pressures. As long as you are following the guidelines given by Goodyear you can run the pressure they tell you. All other trailer tire manufacturers say to use the cold tire pressure maximum inflation rating otherwise you could run into warranty issues.

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Allen B.

6/26/2024

@BudM Thanks for the clarification!

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Bud M.

6/26/2024

@AllenB You're welcome!

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Tim

8/30/2024

@AllenB In my humble opinion, it’s simply that Goodyear has done the tire/wear testing to know the relationship between load and recommended tire pressure while other companies simply have not. This is not surprising for low cost tires since those companies do not have the resources to do the testing. They simply don’t know and leave their customers without guidance. I bought the Goodyear Endurance as well and I use the pressure recommended in their excellent table. https://www.goodyearrvtires.com/pdfs/rv_inflation.pdf I don’t think that you can apply the Goodyear table to other brands, but it certainly true that lightly loaded tires do not need to be inflated to the maximum pressure. After all, it’s the ‘maximum’ pressure and not the recommended pressure for your trailer.m/application. Running at max pressure on a trailer that weighs less than the maximum load capacity for the tire will cause the typical wear pattern of an overinflated tire (faster wear in the center of the tread). If you’re not concerned about this, the maximum pressure shouldn’t cause and danger though it will increase the vibrations transmitted to the trailer which do tend to shake a lot of things loose. ??

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See All (4) Replies to Allen B. ∨

Matt

7/16/2024

Sorry this is wrong and you should correct it because people are looking to you as experts. Very rarely if ever should any tire be inflated to maximum psi. If the trailer has a placard that tells you the pressure and the size is correct, regardless of load range, you should follow that. Maximum pressure reduces the contact with the road which increases breaking distance. Over inflated tire are more prone to punctures. Tire heat induced blowouts are not the only concern here. More accidents are caused by poor handling and locked up brakes than blowouts anyway. A properly inflated tire mitigates all of these concerns. Follow the manufacturers recommendations, not 1970s tire habits.

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Jameson C.

7/16/2024

@Matt False.

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Matt

7/17/2024

@JamesonC hardly, there is a reason that placard is there. And any reputable tire manufacturer has published charts that tell you the same. Tires are filled to the maximum potential weight that they would be carrying, not maximum allowable pressure. What you are advising here is dangerous. Take a tire repair and service certification course and they will advise you the same.

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Jameson C.

7/17/2024

@Matt Vehicle tires have pressure charts but at this time ST rated trailer tires are a different animal and all of the manufacturers will tell you to inflate the tires to their max PSI rating when cold. The only exception being the Goodyear Endurance trailer tires. I know it seems weird but it's not outdated info.

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Pl

2/24/2025

Thank you for your trailer tire pressure article. I have 2 tire pressure questions: - we drive a 2018 Nexus Phantom 35SC. It’s a Super C based on International TerraStar chassis. The tires say max 110 PSI. I have been running them at 90. Are we under inflated? Should I take them up to the 110? - we often tow a car haul trailer with our car on it, total weight 4,700#. I am pretty sure I have been running the trailer pressures below the max pressure. Should I take them up to the max PSI? Thanks so much, PL

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Jon G.

2/24/2025

@Pl Thanks for the questions! Everything that we state about trailer tires goes out the window when it comes to motorhomes. With motorhomes you ALWAYS want to go by what the PSI rating states on the inside of the driver's door frame - just like you would on any passenger vehicle. For trailer tires we recommend running them at the max PSI rating on the sidewall, unless the tire manufacturer has a chart that shows different PSI ratings and different weight capacities. If your manufacturer has a chart like this, then I recommend basing your PSI off of the correct weight rating for your trailer.

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Pl

2/24/2025

I made some mistakes The Nexus RV max tire pressure is 95. I run them at 90 - should I take them up to 95, or will 90 work? Car haul max pressure is 60. I don’t know what pressure I have been running - Should I run them at 60 Thanks again, PL

Reply

Jon G.

2/25/2025

@Pl For your RV, run the tires at the max PSI rating the RV manufacturer tells you to. For your trailer, run the tires at max PSI rating unless the tire manufacturer has a chart showing what to run the tires at for different trailer weight ratings.

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Answer 1

We recommend that all trailer tires be inflated to the max psi stated on the sidewall of the tire. If the tire is under inflated, the weight capacity is lowered to an unknown amount for that tire. Although running lower air pressures can improve the…

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Answer 2

On a towing setup you are always limited by the lowest rated component as the overall towing capacity since that is the weakest point. When it comes to trailer tires you always want to have them inflated to their max psi when cold. Not only do you…

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Answer 3

Trailer tires should be inflated when they are cold and should be inflated to the max psi rating on the sidewall. In your case you would want to run 80 psi. If you don't inflate them to the max psi figure you will lose weight capacity and…

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Answer 4

The psi of your trailer tires will be listed on the side wall. It will list the max psi which is what you will want to fill them to regardless of how much weight you have. For reference, the 4.80 x 12 tires we carry have a 60 psi max for load range B…

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Answer 5

Trailer tires should always be inflated to the maximum air pressure indicated on the tire. The tire on tire and wheel combo #AM30620 for example should be at 90 psi. The reason that you inflate trailer tires to the max is because trailer tires are…

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Answer 6

The radial tire will run cooler with prolonged use on the highway so if this is going to make up the majority of the use then that is what I recommend using. The greatest chance for failure will be out on the highway as pressure and temperatures…

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Answer 7

The Westlake tires ST205/75R15 trailer tires should be inflated to the max psi listed on the sidewall of your tire. The Westlake ST205/75R15 Radial Trailer Tire - Load Range D #LHWL300 we carry should be inflated to 65 psi cold. Ideally you would…

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Answer 8

The correct replacement tire for a 20.2 x 8.0 - 10 is going to be the Loadstar K399 Bias Trailer Tire item #AM1HP56. This is a load range E tire that has a capacity of 1,650 lbs at 90 psi each. It has a speed rating of N which tops out at 87 mph. If…

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Answer 9

Since you have 8K 3" axles you'll just need the Roadmaster Comfort Ride Leaf Spring Suspension Kit w/ Shocks - Tandem 8K, 3" Trailer Axles #RM-2460-2580. The 3-1/2" requirement you were getting with the #RM-2470-2580 was simply…

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Answer 10

The only option we offer to replace the brake magnet spring on a Dexter Electric Trailer Brake Kit (23-434/23-435) part #23-434-435 is with the Replacement Magnet part #BP01-306. We also offer the Replacement Brake Spring Kit part #K71-506-00 if you…

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Answer 11

That's an 8k rated Dexter brake assembly for the right hand side of the trailer which we offer with the part #DX52QR for just the one assembly or part #23-428-429 for both the right and left side.

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Answer 12

The brake assemblies that are on your 8k Dexter axles most would be the Dexter Electric Brake Assembly #23-435, the replacement brake magnets for this assembly would be the Replacement Magnet Kit #BP01-301.

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