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Old 07-14-2016, 03:52 AM   #1
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Tire Temperatures / Pressures

Has anyone used a heat gun to check tire temperatures at different pressures
I have a Newmar 4301 Mtn Aire i had it weighed they told me to run 110 lbs in frount and 90 in rears including tag
The truck shop says i should run 120 all the tires i think the ride is kinda rough .
What do all you suggest ?

Can i check tire temp to see whats happening any ideas on what the normal temps should be ? I have a heat gun .

Thanks for all the anticipated feedback




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Old 07-14-2016, 05:30 AM   #2
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If you have an accurate weight of your axles. Look up your specific tires load inflation tables. Inflate according to it

I personally would not get a heat gun near my tires. I really think you would have zero chance getting any useful information from doing so
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Old 07-14-2016, 05:50 AM   #3
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Real time tire temperature / pressure readings.

I don't have TPMS on my MH, but I installed transmitters in the two rear tires of my TOAD (Toyota Camry) and the two Acme dolly tires. These are pressures and temperatures I seen a few weeks ago while traveling through Arizona with outside air temperatures of 110 Deg.

The TPMS (Schrader) I have shows tire pressure and tire temperature for each tire.

The rear car tires didn't change much, 33 psi cold (85 deg) and they would go to 36 psi warm (130 deg) while traveling

But the dolly tires got a lot hotter,

85 psi cold (85 deg), 105 psi hot (170 deg). On one long downhill where the Acme brakes were probably applied a lot, I seen 200 Deg tire temperatures

(I pulled over and let them cool to below 170 deg before I proceeded)

The left dolly tire seems to run about 10 - 15 deg hotter than the right tire. The Chassis exhaust is on the left side of the MH so the left dolly tire is probably in that hot air stream.

Whenever I stop, I always walk around and check tire temperatures. When I put my hand on the tire and rim, its warm but not what I would consider hot. The outside of the tire is definitely not the 170 deg that the TPMS is reporting from inside the tire. I don't think a heat gun would tell you the temperature inside the tire.

Lesson Learned - tire pressure and temperature change considerably while traveling down the road. always check the pressure when the tire has not been traveling for a few hours and has cooled to air temperature.

ALSO - I was downshifting on the downhills to allow the engine to help with the braking. Acme recommends against this as it keeps the brakes applied on the dolly. They recommend coasting, and use occasional braking to slow down..
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Old 07-14-2016, 06:14 AM   #4
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I'm thinking the OP meant to say hand held no touch thermometer.


Heat Gun????


Yes running your tires at 120 can be a bit hard on the ride.


Truckers use this method since adjusting for different weights when loading is not feasible and down right time consuming.


Now from experience I can tell you, you will get longer life from your tires using the truckers method and maintaining the upper limits of air pressure.


Some if not most of the contributors to this forum will direct you to the RV'ers way and that's to do the calculations after getting an accurate weight of your unit.


I will never argue with anyone set on this way of doing what they believe is right.
After all, there are numerous publications and charts from the manufacturers supporting the weight and calculate method.


Also remember, most RV tires age out of service long before they are worn out over the road like an OTR truck tire.


Me, I like to keep it simple and run my tire pressures to the upper limits where I know I'll never need to consider the load and weight. Single tire pressure for singles, and the lower dual pressure for the drives.


That being said, and to be clear, the tags get aired up to single tire pressure rating also.


DTW
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Old 07-14-2016, 06:25 AM   #5
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DTW et al;

An argument for the higher inflation pressure ??

I suspect that the temperature inside the tire is related directly to how much the tire is flexing from the road contact and the sidewalls. The rubber flexing generates a lot of heat.

A higher inflation pressure would result in less flexing and less heat..

Although lower inflation pressure may improve the ride, After seeing the temperatures from the TPMS, I'm rethinking my cold inflation pressure. I currently run 70 psi in all 6 MH tires based on weight and the tire table, I may take my tires back to 100 psi.

I think on my next long trip, I'll start it out at my 70 psi and take careful note on handling and ride quality for a day or two, then bump them up to 100 psi and see if I can detect any difference in ride and handling.
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Old 07-14-2016, 10:34 AM   #6
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I don't think you can make any useful conclusion from the tire temperature, especially with a infrared wireless type thermometer. They aren't very accurate and the tire surface temp isn't the important thing anyway. It might warn you if you are way under pressure, but it's not going to help optimize anything.

If you weigh the rig and set pressures accordingly, usually with 5-10 psi extra for a safety margin, you will be fine. Or use the recommended pressure from the federal tire placard by the driver seat, which is probably for max rated load. That will be plenty safe too, though maybe a bit rough riding.

Hard to guess where the truck shop came up with "120 psi all the time", but those guys are surprisingly uninformed about proper pressures. They mostly use a one-size-fits-all number, or maybe use the max load inflation off the sidewall. That protects them from ever being sued for under-pressure, but is rarely the right choice.
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Old 07-14-2016, 09:49 PM   #7
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When I got new tires, the truck tire store where I bought the tires inflated all my tires to 100 psi. I asked where they came up with 100 psi. They said they inflate all tires to 100 psi. Let's face it folks, just because someone can sell you tires or install them, it doesn't mean they know a damned thing about tires. They are the guys that were mowing the grass yesterday.
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Old 07-14-2016, 10:45 PM   #8
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I think running the sidewall max pressure is probably safe most of the time. In my case the max is 110psi and tend to run them at 100psi with no issues or alarming conditions. I use a TPMS and watch through out the day for unusual readings. My FW weighs in about 14,500 lbs and I drive between 60 & 65 mph max. I also check the tire pressure every morning before I head out on the road and make and adjustments needed with an on-board CO2 system. My pressure gauge is a digital unit good to +/- 0.5 lbs while the TPMS is not as accurate, think its about +/- 2.5 lbs. What I see is rise from whatever morning air temperature is to perhaps 110 F on a hot sunny day. Pressure rise may go from 100 to about 108 - 110. This varies from sunny side to shady side, windward to leeward wind loading and some to difference in left/right trailer weights. What I watch for is for more than a few psi difference between tires on the same side. I seldom see more than +/- 1 - 2 psi difference in tires. Tire pressure will provide a better overall tire status than temperature alone, because pressure is somewhat an average of temps in different parts of the tire.

I set my TPMS to alarm at temps over 158 F, but never seen them over 112 F. Internal tire temperature varies greatly in different parts of tire, so a single point of data can not tell the entire story what's going on in there, but it does provide a basis much better than no data! At somewhere around 185 F the tire binding chemicals may start to weaken their bonds to the steel and or other fibers in the tire construction. That's where tire failure starts, at that point its starting to fail. I doubt that cooling the tire back down will restore those broken bounds to a safe level, I'd bet the tire will fail sooner than not.

I sure the OP was referring to an infrared thermometer and not a heat gun. I've seen several OPs get the name wrong since the device does have a gun like appearance. I also carry an IR thermometer to mostly check temps of the wheel hubs and not too interested using it to measure tire temp, even though may I may do that too for kicks along with the pavement, the dogs and whatever else maybe near.

In my opinion if you buy one of several quality tires, maintain proper pressure and correct weight loads and drive at or under the rated speed you will have managed your tire risks about as much as you can.

Many happy and safe miles to everyone.
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Old 07-14-2016, 11:18 PM   #9
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Quote:
Originally Posted by ChasA View Post
When I got new tires, the truck tire store where I bought the tires inflated all my tires to 100 psi. I asked where they came up with 100 psi. They said they inflate all tires to 100 psi. Let's face it folks, just because someone can sell you tires or install them, it doesn't mean they know a damned thing about tires. They are the guys that were mowing the grass yesterday.
Rv ers are the new tire experts now I see!! They have probably mowed a few lawns as well.

As someone who used to be in the tire business with some fairly extensive training, and then went into the trucking industry,most people I have talked to in Truck tire shops are pretty knowledgeable. There again if you deal with a reputable dealer you will most likely get a good result. Deal with some of the others and who knows.

Most Rv's as they are manufactured a fitted with tires that will carry the weight of the vehicle plus what ever you put in i. There is a fudge factor in there that will cover some overloading.

The difference in a commercial truck and an RV is that the truck weighs x amount and the load is added later so the tires have to have a load rating to handle that weight.

A motorhome is always near that capacity give or take a few hundred pounds of water or waste.
The recommended pressure on the side of a tire is put on there after alot of testing and is the pressure that will build the less amount of heat for the load carried. They don't put that pressure recommendation on there just to torcher poor rv'ers.

Heat is the worst enemy of tires period.

The same principle applies to pickup trucks if you are not carrying a heavy load in your truck then you can run at a lower pressure,but add air if you are going to load it.

I think I personally would trust the tire manufacturer over the RV manufacturer that want the piece of crap they build to ride better.
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Old 07-14-2016, 11:34 PM   #10
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Quote:
Originally Posted by Waiter21 View Post
DTW et al;

An argument for the higher inflation pressure ??

I suspect that the temperature inside the tire is related directly to how much the tire is flexing from the road contact and the sidewalls. The rubber flexing generates a lot of heat.

A higher inflation pressure would result in less flexing and less heat..

Although lower inflation pressure may improve the ride, After seeing the temperatures from the TPMS, I'm rethinking my cold inflation pressure. I currently run 70 psi in all 6 MH tires based on weight and the tire table, I may take my tires back to 100 psi.

I think on my next long trip, I'll start it out at my 70 psi and take careful note on handling and ride quality for a day or two, then bump them up to 100 psi and see if I can detect any difference in ride and handling.


Waiter21, That's exactly my point and with real experience I know higher pressure within proper limits work.

I've run 10K per month through out the year in all weather, mileage we would never see with our motor homes or trailers.

We just have to make the decision, ride quality or tire performance, and try to split the difference. I for one would be hating life in the motorhome if it rode like it was on solid tire wheels.

So as I said before, I have no argument with a person trying to maintain the highest comfort factor he or she can while operating their coach, just be aware of what you're subjecting your tires to.
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Old 07-15-2016, 12:22 AM   #11
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At risk of being a thread hijacker, I need to comment on Waiters21 comment about coasting downhill- DON'T. I have been driving New Mexico and Colorado mountains for 50 plus years and have been up and down countless mountain passes.

I tow with a RAM 3500 diesel equipped with exhaust brakes and a six speed auto. At the top of downhill I may engage the exhaust brake and downshift to one gear lower than I'd use going up the same grade. My goal is seldom or never need to use the service brakes on a downhill. I intend to get me, my passengers and the rig down safely and without white fingers. If some traffic backups, I'll try to let them pass where I can, but it's not my job to ensure their schedule.

I think if you take the ACME Brake recommendation to coast downhill using your service brakes, they'll be picking you up with a stick and spoon.

Please be safe-
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Old 07-15-2016, 06:44 PM   #12
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"Vsilvester"......I have a 2014 Dutch Star 40' and my guess is that I'm lighter on both the front and rear axles than you. Mine came with 120 psi in the front from the factory and found them too rough. During the first year, while watching tire wear and trying to get the best ride, I settled in at 115 psi. The tires are a little hard at that pressure, but wearing appropriately.

My rears, both drive and tag, are set at 95 psi.

My guess....your heavier, larger coach (without knowing the weights) should be at 115 psi - 120 psi on the front and 95 psi to 100 psi on the rears. You could probably run the tags about 5 psi under the drive tires.
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Old 07-15-2016, 08:42 PM   #13
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Fred, Right on. I'm one of those people that go down the hill in low gear with the flashers on. Im of the opinion that if I need to touch the brakes, I need to slow it down even more and select a lower gear.

I don't ever what to gain experience backing down off of one of those runaway truck ramps..

I'll continue to monitor the temperatures of the Acme tires.
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Old 07-16-2016, 06:36 AM   #14
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I too have a Mountain Aire 4301 and I have both an infrared temperature gun as well as a TPMS with sensors mounted on each of my coach and toad tires.

Knowing the corner weights of your coach is the first and most vital step. By comparing those weights to the weight chart for your tires you'll get the correct tire pressures for your coach. The weights will vary over time and as you move things around so I set my tire pressures at 5 psi above the tire's weight chart and we re-weight each year. The tire guy who suggested 120 psi did not know what he was talking about. For a tractor/trailer, where weights can change dramatically through the day, I can see going with a pressure for maximum weight capacity but a coach's weight is far more consistent so you should be adjusting to your actual weight.

Tire temperatures vary a great deal based upon the outside temperature and even which side of your coach is facing the sun. When I stop, such as at a rest stop, I immediately get out and use the heat gun on all my tires as well as the wheel bearings and brakes on the toad. Tire temps will often go into the 120s but may also be down in the 90s. I forget the critical tire temp but its up around 180 (don't quote me on that number.)

For those using TPMS, forget their temp readings unless their sensors are mounted internally, inside the tire. The external sensors, mounted on the valve stem, are totally useless for temperatures as they give you the outside air temp with very little impact from the actual tire temperature.
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