Trailer tires...Maximum safe pressure buildup

[sixonthefloor]

I have 4 225/75-16 Goodyear G647s on my trailer. They are real close to their 2680# ratings.

A few weeks ago, we left for the weekend, I checked the tire pressure and they were all at 80psi before leaving at about 9 a.m. After about 3 hrs of driving, with an ambiant temperature rise of about 30 degrees (now about 100 degrees), the tire pressure was 94psi.

I am going on a trip from California to Arkansas in July. With the higher temperatures out on the desert (115 degrees or more?) I am wondering at what point I should worry about the pressure buildup? If they reach 100psi do I stop and air down some? 110psi?

I will have an air compressor with me so adding air the next morning, if necessary, will not be an issue.

[JKitterman]

You're never suppose to let air out. Just check them cold and fill to the max. Weigh your trailer axles to make sure they are not overloaded or get new tires with a larger capacity.

[js2941]

I agree, check them cold and go.

[SpikeEng]

Buy a pyrometer and measure the tire temperatures across the tread quickly after a sustained period of towing. The manufacture can probably tell you what the maximum temperature that the tires can handle.

[1BADF350]

Also, if the max tire pressure on these tires is 80PSI, make sure you have the high pressure valve stems on the rims, they have a rubber base (where they seat and seal the rim) but have a brass stem body.
the regular rubber stem style like on car rims, will not last on long pulls. (ask me how I know) grease the hubs prior to leaving and be safe.

[Kaliburz]

Check cold and keep them as close to max as possible (75psi min). Don't worry about hot pressure.

How close are you to maxing them out? 2500? 2000? Distribute your load if possible and check your weights. Have you towed long distance w/ this trailer before? If you are worried about it, get the next load range tire (Don't forget to change the spare too.) Peace of mind goes a long way when towing....

As long as the tires are not weather checked, cracked or have abnormal tread wear, it should be fine. You might think about having them balanced, just in case. But if you have traveled long distance before, you should be fine. Oh, don't forget a spare (in good condition) and to have the correct lug wrenches handy.

[SmokeyWren]

Originally Posted by sixonthefloor

I have 4 225/75-16 Goodyear G647s on my trailer. They are real close to their 2680# ratings.

Those are excellent tires for trailers grossing up to about 10,000 pounds. Goodyear RV Tires || Unisteel® G647 RSS®
But trailer manufactirers tend to install tires that are barely adequate for the GVWR of the trailer. I would weigh the wet and loaded trailer, and if the weight on the trailer axles is more than about 10,000 pounds, I would seriously consider replacing the tires with LT235/85R16E before any long trip.

Your tires are LT and not ST, but that's okay because they are real truck tires rated for "all position", including trailer position. All-position tires cost more than simple pickup tires, but they are available. If you prefer the Goodyear brand, then go with the G614RST in size LT235/85R16G: Goodyear RV Tires || Unisteel® G614 RST® - but note you'll probably also have to also buy new wheels to match the higher-capacity tires.

If you don't want to mess with new wheels, you could go with Michelin XPS Rib in size LT235/85R16E, which will work fine on your 6" rims. They have 3,042 weight capacity @ 80 PSI.

As to "hot" tire pressure, don't worry about it. As the others have mentioned, be sure you have at least 75 PSI cold pressure, then hit the highway and don't worry about PSI.

[sixonthefloor]

Thanks to all who responded.

The trailer, ready for a trip, weighs 11,320. 4860 on the rear axel, 5040 on the front axel and 1420 on the hitch. The tires are rated for 2680 at 80psi. The wheels have metal velve stems.

The trailer came with 225/75-16 Goodyear Wrangler HT tires on it. After 2 years and 3 tire failures, I replaced them with the G-647 tires. A local tire shop really went out of their way to help me. They adjusted the 3 tires that failed and gave me a good price on the 5 new tires.

We have towed the trailer about 23,000 miles in the last 3 years but this is the first time we have been crazy enough to travel across the Southwest desert in summer.

Holiday Rambler in all of their wisdom did not leave enough room for 235/85s and as far as I know there is nothing higher than a load range E available in 225/75-16s. I would not only have to lift the trailer but also put a different suspension on to get enough space between the axels.

After the second tire failure, I put a tire pressure monitor system on so at least I knew right away when the 3rd tire failed.

Maybe I have too much information now. I always check the pressure in the morning with a digital pressure gauge and then put the monitors on. I am just suprised at how much the pressure increase is from morning cold pressures to afternoon hot. A 15 to 17 psi increase seemed like a lot to me.

When I thought about what another 20 degree or so increase in temperatures in addition to what I had already seen could do to the tire pressure the little red lights in my head started going off. I thought "there must be some safe pressure limit that I should not let the tires go past".

Oh well, I guess I will only worry if the pressure goes down while I am towing.

Mark

[Kaliburz]

Mark,

Another thing you can do to speed up checking the PSI is thump the tires w/ a hammer. After a while, you'll be able to tell if one is low or not. Takes time, but a good ear can tell.

No room for bigger tires. Dang. That sucks.

[js2941]

I use the G614's with standard wheels, but I only inflate to 80psi, that's all I need for my application.

[spg]

What about a LT245/75-16 that is rated at 3042#? They are not quite as big as the LT235/85-16.

[bigdawgkp]

Hey sixonthefloor - go have a tire company replace the air in your tires with nitrogen. Nitrogen is inert and will remain a constant pressure. Put in your truck tires also. Get the tire company to change the air caps from black to green. You won't have any further problems. Have a splendid day! bigdawgkp

[Mark Kovalsky]

Originally Posted by bigdawgkp

Nitrogen is inert and will remain a constant pressure.

Being inert does not mean that the gas does not obey the gas law. Inert means it won't easily combine with other elements. Nitrogen WILL expand with temperature, almost EXACTLY the same amount that air will, regardless of the hype that the tire stores are putting out. Air is 79% nitrogen.

Nitrogen will reduce the increase in tire pressure with temperature by an amount that is too small to read on most tire pressure gauges.

[bigdawgkp]

So is it good or bad to put nitrogen in your tires Mark?

[spg]

Won't hurt to use nitrogen. It just won't affect the pressure build up much.