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Old 07-16-2019, 10:36 AM   #15
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Originally Posted by rameyer84 View Post
Just got a TST tire pressure monitor and tried it out last weekend on a short trip. Have Sailun tires on an 18,000 lb. fifth wheel that registered 106 to 108 psi before hitting the road.
What is your cold tire pressure supposed to be set at, and what is on the tire sidewall? 106 seems high to me. Typically it's 80 psi. 120 would make me nervous.

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Old 07-16-2019, 11:14 AM   #16
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Originally Posted by mobilemike View Post
There is a reason the tire pressures are set COLD.

The engineers have calculated the increase in pressure when running hot.

Set them at the pressure you need for the load and disregard the pressure increase when they get hot. Its part of the equation already.

It wasn't too many years ago that the rule was to just set all trailer tires to "Cold Max". Then tire charts became available and now the rule is to weigh the axles and set the PSI according to the tire load. As more tools become available and used, tire pressures will continue to be fine tuned for the best operating PSI.
A tire on the road at 20 PSI over "Cold Max" may be OK for days past, but could stand to be fine tuned.
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Old 07-16-2019, 11:49 AM   #17
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Originally Posted by dkegel View Post
What is your cold tire pressure supposed to be set at, and what is on the tire sidewall? 106 seems high to me. Typically it's 80 psi. 120 would make me nervous.

Dave
Max cold temp is supposed to be 110 psi.
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Old 07-16-2019, 12:50 PM   #18
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Yep and they also will very in temperature rise also. Tires are designed to do this that is why they state cold pressure inflation readings. And you should wait at least 4 hours if not overnight when traveling before checking the tire air pressures.

This use to be taught in automotive mechanics in high school when I went to school.
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Old 07-16-2019, 03:03 PM   #19
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Yep and they also will very in temperature rise also. Tires are designed to do this that is why they state cold pressure inflation readings. And you should wait at least 4 hours if not overnight when traveling before checking the tire air pressures.

This use to be taught in automotive mechanics in high school when I went to school.

Exactly my point, things have changed since old school teachings ie: tire pressure charts, TPMS.
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Old 07-17-2019, 10:01 AM   #20
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It wasn't too many years ago that the rule was to just set all trailer tires to "Cold Max". Then tire charts became available and now the rule is to weigh the axles and set the PSI according to the tire load. As more tools become available and used, tire pressures will continue to be fine tuned for the best operating PSI.
A tire on the road at 20 PSI over "Cold Max" may be OK for days past, but could stand to be fine tuned.
100% correct. That is why I said "set the tire pressure you need" and disregard the increase due to the heat of driving.
Even with tire charts and adjusting for weight the pressure is still set COLD with no adjustment for heat increases in pressure.

Actually as the tire gets warm it becomes softer and will flex easier and benefits from the increase in pressure.
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Old 07-17-2019, 10:48 AM   #21
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I have a 15400 lb fiver with GY 17.5 114 tires. Max psi is 125 and I keep them cold pressure 115.
On our Memorial Day week trip to the Panhandle with ambient air temps at 100 degrees, here is what I experienced: Tire temps from 105 - 111 degrees and psi 130-132.
My front axle right side tire was always the highest I presume due to it getting a lot of exhaust heat especially during regen cycles.
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Old 07-17-2019, 03:24 PM   #22
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My tires state 110 PSI cold inflation pressure and that is what I put in them!

If you put in less air pressure on ST tires, this will cause the side wall to flex under load more and could lead to premature tire failure.

I have never seen a tire inflation pressure table for ST tires on the internet. If I was still at Cat, I probably could lay my hands on a Tire and Rim Association handbook to check what a ST tire inflate table stated as far as tire load to inflation pressure. But since I am not a stick to what is on the sidewall for cold tire pressure requirements.
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Old 07-17-2019, 06:33 PM   #23
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Jim,
Go to the GY web site and see the recommended ST tire pressures for various loads based on the tire load range. I use the one dedicated to the GY Endurance various sizes for the best pressure, and with that pressure at takeoff I feel safe and confident regardless of the varying temps I experience during the trip. I also have never seen the Endurance at those recommended pressures exceed the TPMS limits for an over-pressure alarm.
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Old 07-17-2019, 06:50 PM   #24
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Originally Posted by grindstone01 View Post
It wasn't too many years ago that the rule was to just set all trailer tires to "Cold Max". Then tire charts became available and now the rule is to weigh the axles and set the PSI according to the tire load. As more tools become available and used, tire pressures will continue to be fine tuned for the best operating PSI.
A tire on the road at 20 PSI over "Cold Max" may be OK for days past, but could stand to be fine tuned.
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Jim,
Go to the GY web site and see the recommended ST tire pressures for various loads based on the tire load range. I use the one dedicated to the GY Endurance various sizes for the best pressure, and with that pressure at takeoff I feel safe and confident regardless of the varying temps I experience during the trip. I also have never seen the Endurance at those recommended pressures exceed the TPMS limits for an over-pressure alarm.

Current recommendation from Roger and other tire engineers I've talke to:
For towables - (5th wheel and bumper pull trailers) inflate to max cold inflation pressure. End of discussion


For other vehicles (class A, B, C, etc and trucks when hauling stuff in the bed) use the available inflation pressure charts for actual loaded weight. Be sure to use the pressure required for the heaviest tire load per axle. (Really, you should have individual wheel weights, not 50% of total load on an axle).
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Old 07-17-2019, 09:04 PM   #25
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Your opinion is just that. The experts have data and knowledge in what they advise . Not opinions. Set your air pressure at recommended levels relative to the weight they carry. Goodyear has a chart for that. Letting air out is a waste of time unless your inflation is over when the tire is cold . That is not old school that is today. TPMS is a tire monitor that's it. Monitor .
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Old 07-17-2019, 09:18 PM   #26
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Is it already time for another tire pressure thread? We have at least 1 still running.


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Old 07-18-2019, 08:02 AM   #27
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My Sailuns do the same thing. I will start out at 105 PSI and have seen them go up to 128 PSI on a hot day.
I have been challenged many times for this, but I will try to keep my rolling PSI down to around 120 PSI which may require letting some air out.
My opinion/thought is that the tires running at 128 PSI are overinflated and besides wearing the center thread, they make for a hard ride on the trailer.
Don't be afraid to fine tune your tire PSI now that you know what they are doing while going down the road. Just because the old school said to set the tires at cold temp and leave them alone, doesn't mean it can't be improved as better tools (TPMS) give us more information.
I comply with setting cold pressures but when I first got this rig and set cold pressures IAW actual weight I found my computed pressures were at the top end of values in the Tire and Rim tables. After two blowouts I changed the tires to stronger tires. I still set my cold pressures IAW weight but my hot pressures are still in range of pressures listed for cold pressures listed in the Tire and rim tables. I feel a lot safer this way. So I remain skeptical about hot pressures being unimportant.
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Old 07-18-2019, 10:01 AM   #28
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Mobilemike is 100% correct. Back when I fished the tournament trail we ran Goodyears as did most other teams. Blowouts and bubbled sidewalls were common and all of us were running under max due to being under max weight with the idea we would have a better ride.

Goodyear took us to school on this when many of us were raising cain about it. According to the Goodyear engineers trailer tires inflated to MAX pressure in the morning when cold. They even have a formula so you can measure cold and then add air later to above max when warm to what it should be. The tires do get more flexible when warm and do benefit from the extra pressure-that pressure is like a frame supporting your house. When the pressure is low the tire “bags” more at the bottom causing increased back and forth flexing of the sidewall (wider/skinnier/wider/skinnier) as it rotates, creating more friction heat. So also if you inflate to max that tire will actually warm LESS than a tire inflated under max. Those with TPMS can see this firsthand if you run 2 different pressures on the same side of the trailer.

Since changing my practice to this in 12 years of heavy towing I have never had a tire failure of any brand not due to puncture.
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