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Trailer tire air pressure question #4107347 05/26/16 03:09 PM
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silveravant Offline OP
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I have a trailer for my racing sailboat. The boat only weighs 515 lbs. and the trailer weighs at most 500 lbs. (total 1015 lbs.) The tires are 5.30x12, load range C rated for a max load of 1045 lbs. at 80 psi. I know that with trailer tires you are supposed to run the psi on the tire, but because the tires are only carrying about half their rated load would it be OK to run a little less pressure for a little softer ride? They seem pretty hard at 80 psi.

Re: Trailer tire air pressure question [Re: silveravant] #4107353 05/26/16 03:16 PM
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krismoriah72 Offline
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with the combined weight that you specified i wouldnt run less than 75psi.

You need the 75-80 PSI or the tires will run hot and fail. At 55 PSi too much sidewall flex = heat.
The air carries the load.

Re: Trailer tire air pressure question [Re: silveravant] #4107362 05/26/16 03:28 PM
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Rand Offline
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is it really bouncy towing?

Best practice is to run near the tire's max psi because bias ply sidewalls are very stiff and can create alot of tire destroying heat if under inflated.

If you are only going short distances it is probably fairly safe to drop that down some.. maybe 60-65psi.

or replace the tires with some 50-55psi max ones.

I have in the past with the utility trailer hauling light load 80psi it feels like its bouncing a foot in the air on expansion joints.

Originally Posted By: krismoriah72
with the combined weight that you specified i wouldnt run less than 75psi.

You need the 75-80 PSI or the tires will run hot and fail. At 55 PSi too much sidewall flex = heat.
The air carries the load.


he is running ~1050lb on tires rated for near 2100lb (pair)


2019 Jeep Cherokee Trailhawk 2.0T
2020 Hyundai Elantra "Value Edition"
Re: Trailer tire air pressure question [Re: silveravant] #4107417 05/26/16 04:43 PM
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CT8 Offline
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Don't go too fast with the tiny diameter tires.


2015 F150 2.7
2018 F350 6.2
Re: Trailer tire air pressure question [Re: silveravant] #4107420 05/26/16 04:47 PM
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BrocLuno Offline
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Drive down the road for 20 miles, stop and feel the tires. Are they hot, warm, or just about the same as the car? If cool, drop pressure and cruise on. Stop another 20 miles and see how they feel... Repeat until you get them just slightly warmer than your car tires. That's as low as you can go. Now go back up 10 psi for margin.

Just like a race car, 4x4, or a dune buggy; you need to adjust air pressures to get what you want. A smart driver knows what his vehicles are doing including how the tires are running. Work it out to get the best ride and the longest tire life.

The tire MFG has no way of knowing how you will use your tires. So they opt for max safety under full loaded conditions. If that's not how you run, that is not the pressure needed ...


Formerly in marine engineering. In an earlier life I owned my own petroleum tank truck, and hauled for the majors and independent's.
Re: Trailer tire air pressure question [Re: silveravant] #4107454 05/26/16 05:40 PM
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EdwardC Offline
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I don't know what kind of trailer it is, but I'm assuming it is way over rated for your 500# load.

If you primarily only haul the sailboat or other relatively light loads, it's not uncommon (at least on teardrop trailers) to remove one of the leaves on the spring, and to further improve the ride, add some trailer shocks.

Then you can keep the tires at the pressure they want, while giving your sailboat a smooth ride.

Re: Trailer tire air pressure question [Re: krismoriah72] #4107473 05/26/16 06:04 PM
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abycat Offline
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Originally Posted By: krismoriah72
with the combined weight that you specified i wouldnt run less than 75psi.

You need the 75-80 PSI or the tires will run hot and fail. At 55 PSi too much sidewall flex = heat.
The air carries the load.



I second this. Do tractor trailer tires get aired down when empty? nope!


2017 dodge caravan gt
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Re: Trailer tire air pressure question [Re: silveravant] #4107477 05/26/16 06:07 PM
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Toaster_Jer Offline
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The tires will run the longest at max air pressure. The tread will wear uneven with less air pressure.

Re: Trailer tire air pressure question [Re: silveravant] #4107507 05/26/16 06:40 PM
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OK, the first step is to factor in how much load is on the tires. If the whole rig weighs 1015#, and between 10% and 15% is on the tongue, the load on the tires is a max of 914# = 457# per tire.

Second step is to account for side to side weight variation - and in the absence of actual weights, let's assume there is about a 10% variation = 503#.

And my rule of thumb is that no tire should be loaded to more than 85% of its rated load at the usage pressure = 592#.

So the load chart says 30 psi if you want to be speed limited to 65 mph, 40 psi for 66 to 75 mph, and 50 psi for 76 to 85 mph.

Now that a bit of a jump, so I suggest you lower the pressure in 10 psi steps and follow the 10% rule of thumb: You don't want more than a 10% pressure build up after an hour and 1/2 of driving.

Last edited by CapriRacer; 05/26/16 06:41 PM.

CapriRacer

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Re: Trailer tire air pressure question [Re: silveravant] #4113245 06/02/16 10:16 AM
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silveravant Offline OP
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Thanks for all the thoughtful replies. I will try 60 psi on my next trip and monitor the pressure and temperature.

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