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Old 07-29-2010, 09:06 AM   #43
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I use Maxxis E's on my 25 Safari, going into my fourth season with no problems. I think LT tires are the way to go, but I didn't want to spend the money to upgrade to 16" wheels.
Blew up 4 D rated Marathon's, one within 400 miles of purchase despite being careful about speed and tire pressure.
If you tow a lot of miles at freeway speeds in very hot weather you will have blowouts with GYM's and other D rated ST tires, guaranteed.
I have towed a lot of miles with my Maxxis', some in Mexico where the roads are bad and some on gravel secondary roads and have had zero problems with popped rivets, torsion axles or other problems allegedly due to stiff tires.
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Old 07-29-2010, 09:07 AM   #44
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Tire pressure should level out after 1.5 hours steady state driving. Gene, are yours really gaining 15-psi? Sounds too much from cold to hot.
Most of our last trip had morning temps in the 40's, sometimes upper 30's. As we drove south, things changed, and suddenly, back in the US, afternoon temps were in the 90's and morning temps were in the 50's. At noon, psi may be up 10 lbs at 90˚, but by 4 pm, temps are in the mid-90's and psi goes up some more. Alarms go off, lights flash. Within a few minutes all the alerts for each tire are going off. It's then time to stop and let some air out. The next morning, I might remember to let more air out to establish cold pressure for that day. And by afternoon, further south, temp goes up to 102˚ at Provo, down to the mid 60's crossing Soldier Summit in a rainstorm, and then up to 106˚at Green River. Let out some more air. What's a tire to do?

If the temp stayed the same and I adjusted the pressure more often, alarms wouldn't go off. With 40 or more degree swings in temp in one day, things get crazy.

Since I'm using Load Range E tires on the trailer, it would be very hard to have too much pressure. After looking at how much pressure supports how much weight with these tires, I figured 68 psi was right for them. Since they are wearing evenly, I guess it's working. If I start out in the morning at 70 or 71, that's within the margin of error for the various pressure gauges (the TPMS readings, the hand held unit, and the one on the compressor, all of which read differently, but with a 3 pound range). The TPMS alerts go off at 81 psi (+13 psi) and psi may go up more before I stop. Since these tires are designed for up to 80 psi cold, they can be well above 80 psi while driving without harm.

If I stay at the same climate zone all day, tire pressure levels out quite fast. And, I should probably reduce morning pressure more often. The Marathons did the same thing when I drove through different climates—sometimes snow in the morning, thunder and tornado threats in the afternoon. In November we have gone from the teens in the morning in Colorado to summer in Arizona in a few hundred miles.

Gene
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Old 07-29-2010, 09:08 AM   #45
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I have been using GoodYear trailer tires since 1977 and have been very satisfied with their performance. Recently, after 4 years and 9 months, I did have a tire start to fail. I bought a Marathon replacement. I specified to inflate the new tire to 60psi. When I returned to pick up the tire at the shop I noticed that they had installed the wrong vavle stem. These tires need to have high pressure valve stems. After I returned home with the tire I checked the air pressure and got a reading of 30psi. If I had installed this tire on my trailer with the wrong valve stem and under inflated think of what would have happened.

What did you do? Did the dealer change the stem?

Thanks!

Gary
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Old 07-29-2010, 09:45 AM   #46
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Could it be that...
it's more likely that THIS bit of info (from da'rock) is MISinfo...

like so many other "they said" bullets in this thread.



cheers
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Old 07-29-2010, 10:26 AM   #47
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there is almost NO REASON to let air OUT of a tire during the day while driving.

in almost all situations it is a BAD IDEA that produces more problems than good.
_________

there was a time when this practice MIGHT have been occasionally useful.

but is ANYone here still using COTTON bias ply tires?

do you have a tendency to COOK the brakes after COOKING the transmission?
_________

internal tire pressures change ~1 psi for every 10 degrees F of air temp.

so going from 20 F to 100F is still only a 8 psi shift.

altitude also impact internal tire pressures, about 2-3 psi over 10,000 ft of elevation change.

traveling UP may add 1-2 psi in the rockies, but is largely offset by COOLER air temps at altitude.

traveling DOWN will lead to warmer air temps, but the drop in altitude drops pressures too.

unless one is COOKING the brakes on the downslopes.
________

MODERN radial tires have "blow off the bead" pressures that are ~ 1.5-2x max cold inflation.

so a 50 psi tire is built to handle up to ~100, while an 80 psi tire perhaps 140 psi.

altitude and HOT day/cold day tolerances are BUILT IN to the tires.

even IF driving conditions or habits resulted in a 20-30 psi gain, the tires can TOLERATE that shift.

do NOT muck around with pressures on hot days.
________

no tire made "gains" air during use...

so letting air OUT always means UNDERinflation eventually, often the SAME DAY.

no tire made "leaks" air either

(unless it's latex, gotta hole or faulty stem/rim seal)

these are OLD GUY tales (wives musts listen too no doubt)

based on childhood-man myths passed on via the Y chromosome.
_________

a tire that gains SIGNIFICANT pressure during use

(not related to temp/altitude) is mosts likely UNDER INFLATED.

ADD air and the relative gain with use will go down.
_________

the ONE exception to all of the above is

travel DOWN HILL over LONG LONG stretches using TOOO much brake...

the hub/drum/wheel heat may be significant and heat up a tire WAY beyond 40 or 50 degrees.

this is pretty UNCOMMON now,

and again who's still running cotton ply tires?

cheers
2air'
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Old 07-29-2010, 01:18 PM   #48
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there is almost NO REASON to let air OUT of a tire during the day while driving...

cheers
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Agreed. Tire pressures are specified cold. This specification takes pressure gain from driving into account. Any necessary adjustments to tire pressure should be made to cold tires because it is extremely difficult to accurately keep track of pressures as driving conditions change. Even the racing people make their adjustments to cold tires.
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Old 07-29-2010, 01:59 PM   #49
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No question tire pressures are supposed to be measured when cold. When I reduced pressure on the road in the afternoon, the next day they were still about 2 lbs. high in the morning when cold pressure was determined at 80˚. If I had gotten up at dawn, the pressure probably be close to optimal. Reducing pressure during the afternoon does not mean tires will be underinflated at some other time—it depends where you are traveling, climate, weather.

If I had let out a little air in Canada before it got really hot, the TPMS would not have gone off further south. I started out the day several pounds overinflated through Alberta and into Montana. When the alerts started, pressure probably went up 8-9 lbs. or so, though it was 13 lbs over what the TPMS was set for (alerts go off at +20% of what it is set for). I didn't make that clear before. Altitude was increasing also, perhaps 3,000' or more just as temps were increasing.

So it's best to check pressures at the coldest part of the day, but I'm not about to get up at dawn and stumble outside to check tire pressure. It's nice to get this right, and "right" is subject to lots of things. Gauges differ, for example. Watching how pressure changes gives a pretty good idea of what's going on. The alerts always happen on the sunny side first. In a cloudy, rainy place, tire pressure doesn't change much at all especially if driving slowly, at least compared to going 65 across the desert in the sun as temps go up 10˚ every hour or two for a while. If you have an idea how much pressure increases in different situations (watching the TPMS monitor makes that possible), adjusting pressure at the "wrong" time can work fine, but it takes some careful observation. Since the tires I'm using can be pumped up a lot more before they explode, I don't worry about them being several pounds high in the morning—but it does make it possible for the TPMS to drive us crazy by afternoon.

I have noticed that tires exposed to the sun in the morning are about 2-3 lbs. higher than the tires out of the sun. So, when checking tires after the sun has risen, it seems best to check the ones out of the sun first, establish how much to add or subtract from those and then add or subtract the same amount from the sunny side. The sunny side will show some overinflation, but that is caused by the sun heating and isn't actually cold pressure. Even after the sun has risen, temps may still fall for a while, but not for long.

Gene
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Old 07-29-2010, 03:04 PM   #50
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..Reducing pressure during the afternoon does not mean tires will be underinflated at some other time...
sure it does.

IF they started out at the proper inflation.

Quote:
Originally Posted by CrawfordGene View Post
...
So it's best to check pressures at the coldest part of the day, but I'm not about to get up at dawn and stumble outside to check tire pressure. ...
actually "cold inflation" just means not HOT from driving.

so 3-5 hours parked is adequate to check for baseline pressures.

yes if it's 100 out AND the sun in full blaze the pressures will be little higher than 'cold'...

but only 1-3 psi (so a reading of 53 psi could be considered as 50)

and the entire bit about shade/sunny side teak 1 side before the other

is OVER inflated thinking.

turn OFF the tpms or get one that allows SETTING the over/under signals.

cheers
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Old 07-29-2010, 08:47 PM   #51
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sure it does.

IF they started out at the proper inflation.



actually "cold inflation" just means not HOT from driving.

so 3-5 hours parked is adequate to check for baseline pressures.

yes if it's 100 out AND the sun in full blaze the pressures will be little higher than 'cold'...

but only 1-3 psi (so a reading of 53 psi could be considered as 50)

and the entire bit about shade/sunny side teak 1 side before the other

is OVER inflated thinking.

turn OFF the tpms or get one that allows SETTING the over/under signals.

cheers
2air'
"Proper inflation" is not a constant that can only be changed when tires have been resting for 3-5 hours. Knowing how much pressure increases during driving can show how much would be proper if the tires were at rest.

"Cold" can mean either morning or at rest, but with afternoon heat "cold" means higher pressure than it did in the morning. Your previous post said "~1 psi for every 10 degrees F of air temp." I don't know where that number comes from, but it seems close to reality. With swings of temp of 40˚ not uncommon and 50˚ or more not unusual, it adds up. The increases in pressure I reported are a combination of more pressure (1) due to driving, (2) due to higher air temps, (3) not changing "cold" pressure when I could have, (4) maybe altitude. Compensating for the sunny side is easy if the sunny side is always the sunny side.

If you let air out in the afternoon while they are at rest it is the same as letting it out when they are hot—by knowing how much the pressure increases while driving, and then compensating for that, you can come pretty close to knowing what "cold" pressure would be at that time of day. In fact, I was about 2 lbs. high, intentionally, to make sure I didn't let too much out.

If all other factors remain constant, how much does pressure increase while driving 55-65 mph? Sadly, I forget exact numbers, but I think they were around 4-6 lbs. So 5 (driving) + 5 (50˚ temp increase) + 1-2 (warmer morning temps) + 1 (altitude) = 12-13 lb. increase, very close to what I experienced.

My experience is that the temp doesn't determine most of the difference between sunny side and dark side. It doesn't have to be 100˚. The difference when I measure it is 2 to 3 lbs. (you say 1-3, maybe; that's not a significant difference). It is a factor more of sun, less of temp. You can consider it "OVER inflated", I think it's just another factor in getting pressure reasonably correct. But the 1-3 may be a combination of sun vs. dark side and temp changes—your meaning is unclear. That would contradict your earlier statement that pressure increases about 1 lb./10˚, so I'm taking it as only referring to sun vs. dark.

Gene
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Old 07-29-2010, 09:02 PM   #52
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I have checked my tires in the morning and yes the tires in the sun will be 2-3psi more than the tires on the other side. There is lots of energy in the sun, it melts ice off pavement when its 20 degrees outside.
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Old 07-30-2010, 04:39 AM   #53
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What did you do? Did the dealer change the stem?

Thanks!

Gary
As the attendant was loading the tire into the trunk of my car I noticed the wrong valve stem. He took it back into the shop. I waited for several minutes and finally asked what was taking so long. They were out of the high pressure valve stems and were waitng for some to be delivered.
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Old 07-30-2010, 08:37 AM   #54
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As the attendant was loading the tire into the trunk of my car I noticed the wrong valve stem. He took it back into the shop. I waited for several minutes and finally asked what was taking so long. They were out of the high pressure valve stems and were waitng for some to be delivered.

Thanks for the heads up on the stems. I saw yesterday at one tire store they had three stems: rubber stems, high pressure stems, and all metal stems.

Gary
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Old 07-31-2010, 10:25 AM   #55
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The deed is done. Got the Marathons put on yesterday. Made in USA date 21-10. All metal stems. I got a 5th for a spare but I haven't found a wheel yet.

Wheel bearings all packed, and brakes set up. Now to try the brakes. There's a load on the brake circuit bare wires. I assume that's the resistance from the magnets. I read on a horse trailer forum that the magnets will show a close on the circuit. I'll try em out today.

Sidebar: The PO had disconnected the break away switch. I have a new one that I'll wire according to EOM specifications.
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