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  1. #1
    Member Tim W's Avatar
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    Tire pressure question

    I haven't put air in my tires since the tires were mounted (about 1.5 years ago). I checked my air and all were about 40psi. The side wall says MAX psi 65. Should i run 65 psi? The trailer is the one in the signature.

    Thanks.

    Triton 19 XS Elite, 225 Mercury Pro XS, Minn Kota Ultrex 112, Hydrowave H2, Twin 10' Power Pole Blades, Lowrance HDS 12 and 12 at console, Lowrance HDS 9 at bow, Mercmonitor, Rigid Industries Deck lights and other stuff to come that will make me go more broke

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  3. Electrical/Wiring/Trolling Motors Moderator CatFan's Avatar
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    #2
    65psi without a doubt.
    Remember, Happiness is a way of travel, not a destination.

  4. Member Tim W's Avatar
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    #3
    I just read that in the sticky. Thanks cat

    Triton 19 XS Elite, 225 Mercury Pro XS, Minn Kota Ultrex 112, Hydrowave H2, Twin 10' Power Pole Blades, Lowrance HDS 12 and 12 at console, Lowrance HDS 9 at bow, Mercmonitor, Rigid Industries Deck lights and other stuff to come that will make me go more broke

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    #4
    I check my tire pressure before pulling out of the driveway every single time I haul. Just becomes part of the pre-trip routine.

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    #5
    Quote Originally Posted by billwvu05 View Post
    I check my tire pressure before pulling out of the driveway every single time I haul. Just becomes part of the pre-trip routine.
    What he said.

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    #6
    I got this TPMS last week and towed with it the first time today. Love it.

    http://www.tiretraker.com/proddetail.php?prod=TT500-4

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    #7
    Quote Originally Posted by toofy View Post
    I got this TPMS last week and towed with it the first time today. Love it.

    http://www.tiretraker.com/proddetail.php?prod=TT500-4
    I also have a tire pressure monitoring system I run all the time while towing. Mine is made by TST. There are several good ones out there. Now they are obviously not going to help if you have a tread separation blowout, but they can alert you to a pressure/heat problem that you can avert. One thing I have to deal with here in Texas is road heat in the summer. So when it looks like the road heat is increasing the tire pressure to much, I can make an adjustment before I get into trouble. I have pulled over and done that twice last year when I was doing a long tow. The tire manufactures do a good job of telling you what your max cold operating pressure should be, but not when the heat raises your tire pressure.
    Last edited by Tromanoski; 02-05-2018 at 10:38 AM.

  9. Electrical/Wiring/Trolling Motors Moderator CatFan's Avatar
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    #8
    Quote Originally Posted by Tromanoski View Post
    The tire manufactures do a good job of telling you what your max cold operating pressure should be, but not the hot.
    The cold max pressure allows for the pressure rise when hot unless the heat is caused by significant environmental change. If you lower the pressure while the tires are hot from use, you are underinflated.
    Remember, Happiness is a way of travel, not a destination.

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    #9
    Quote Originally Posted by CatFan View Post
    The cold max pressure allows for the pressure rise when hot unless the heat is caused by significant environmental change. If you lower the pressure while the tires are hot from use, you are underinflated.
    So Cat Fan. When I start out at 65 cold psi and Im running down the road at 75 mph and the outside temperature is 98 to 100 degrees, I should not make any adjustment to my tire pressure when it is going to exceed the 20% max pressure that the TPMS company tells me to set for the high pressure alarm? I have on two occasions this past summer hit that high alarm, pulled over, took a couple of lbs out of the tires and moved on down the highway. Tire pressure after the adjustment never dropped below 69 to 70 lbs. If Im doing it wrong then that good to know.Like I said I have not been able to find any information about how high a pressure is safe when its from heat build up.

  11. Electrical/Wiring/Trolling Motors Moderator CatFan's Avatar
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    #10
    Quote Originally Posted by Tromanoski View Post
    So Cat Fan. When I start out at 65 cold psi and Im running down the road at 75 mph and the outside temperature is 98 to 100 degrees, I should not make any adjustment to my tire pressure when it is going to exceed the 20% max pressure that the TPMS company tells me to set for the high pressure alarm? I have on two occasions this past summer hit that high alarm, pulled over, took a couple of lbs out of the tires and moved on down the highway. Tire pressure after the adjustment never dropped below 69 to 70 lbs. If Im doing it wrong then that good to know.Like I said I have not been able to find any information about how high a pressure is safe when its from heat build up.
    Depends. If you start the day at 65psi at 4am when it's 70 degrees out, and then while you are running the air temp rises to 100, you might have a small issue. As a rule of thumb, a 10 degree change in tire temp gives a 2% change in tire pressure. So if your cold pressure at 70 degrees was 65psi, then if the ambient increases to 100 your pressure will theoretically be 3.9psi too high if you parked and let it cool to the ambient temp.

    Using the rule of thumb, a 20% pressure rise from heat would correspond to roughly 100 degree increase in tire temperature. If your tire temperature started out at 70, to get a 20% increase in pressure you'd be seeing tire temps at 170 which is above the threshold TST recommends for high temp. Dropping pressure then is going to increase heating.

    Temperature readings from the TST is a bit suspect though since temperature varies within a tire. Probably only useful in comparing to the other tire on that side of the trailer.

    Just as a data point, I have a TST 507 that I use with my 5th wheel weighing around 11,000lbs. When I travelled last summer to see the solar eclipse, we had highs in the mid 90s. I hit the road at 80psi and saw maximum pressures of 92-93 while travelling in full sun at 65-70 on the interstate. I can't remember tire temps, but they never alarmed for heat and it is set at 158 IIRC. I remember the pressures because I had my alarm set for 92psi on the first leg of the trip and had to remedy that at my first fuel stop.

    A couple of things I've found interesting is the tire temperature difference on the side in direct sunlight and the effect of heavy rain on temps and pressures. I hit a fairly heavy rain while travelling with tires at the 92-93 range, and pressures and temps quickly dropped to ambient. I slowed down a little, but not a lot.
    Remember, Happiness is a way of travel, not a destination.

  12. Member rocket man's Avatar
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    #11
    So on a very hot day with bright sunlight if the pressure rises more than 20% should you let some out.? Or leave it alone.?

  13. Electrical/Wiring/Trolling Motors Moderator CatFan's Avatar
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    #12
    Quote Originally Posted by rocket man View Post
    So on a very hot day with bright sunlight if the pressure rises more than 20% should you let some out.? Or leave it alone.?
    Honestly I think you should investigate the problem. Something isn't right if your tires are running 100 degrees over ambient.
    Remember, Happiness is a way of travel, not a destination.

  14. Member rocket man's Avatar
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    Quote Originally Posted by CatFan View Post
    Honestly I think you should investigate the problem. Something isn't right if your tires are running 100 degrees over ambient.
    No Not temp PSI

  15. Electrical/Wiring/Trolling Motors Moderator CatFan's Avatar
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    #14
    Quote Originally Posted by rocket man View Post
    No Not temp PSI
    20% pressure rise indicates about a 100 degree temperature rise.
    Remember, Happiness is a way of travel, not a destination.

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    #15
    My tire temperature only exceeded 100 degrees not my tire pressure. My tire pressure had a 20% increase in pressure twice this past summer when it was 100 degrees here in Texas.. Tire temps were around 105 degrees especially on the exhaust side of the truck. So on those two occasions I let a couple of lbs of air out of each tire. Pressures stayed well above the 65 PSI but below the 20% increase. I don't know if that was the right thing to do or not.

  17. Electrical/Wiring/Trolling Motors Moderator CatFan's Avatar
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    #16
    Quote Originally Posted by Tromanoski View Post
    My tire temperature only exceeded 100 degrees not my tire pressure. My tire pressure had a 20% increase in pressure twice this past summer when it was 100 degrees here in Texas.. Tire temps were around 105 degrees especially on the exhaust side of the truck. So on those two occasions I let a couple of lbs of air out of each tire. Pressures stayed well above the 65 PSI but below the 20% increase. I don't know if that was the right thing to do or not.
    If it was 100 degrees, your tire temps had to be over 105 at interstate speeds. You would see very little pressure rise at 105 degrees.
    Remember, Happiness is a way of travel, not a destination.

  18. Member rocket man's Avatar
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    #17
    I can remember the first time I used the TST in early spring. The psi went from 65 to 74 but the temp never got over 84 degrees.