Maybe why those tires from China blow - Montana Owners Club

Mudchief · 05-17-2009, 01:36 PM

We took a short weekend trip to check out my new toy the Doran RV 360 tire pressure system. When I started the trip all tire showed 80 pounds except for the front on the truck which I run at 62. About 1 hour into the trip the trailer tires all ran between 90 and 94 pounds. I was getting close to the high pressure alarm going off.The truck tires on the back were showing 82 and 83 and the front was 64 each. I stopped and removed the sensors and check with my tire gauge and it showed that they were in deed all high. The next morning all tires read where they should. I stopped by a CAT scale and weighed the trailer and it showed 10,401 which is below the rating for the tires. Now this was on a 80 degree day can you imagine what it would have been on a 100 degree day. All of my Mission tires were just replaced by the tire company with another brand tire also made in China. Maybe I should be running 70 in them instead of 80 that way when they heat up they will be in the proper range.

Glenn and Lorraine · 05-17-2009, 02:17 PM

Actually you may be correct if in fact your 2 trailer axles weigh in at 10,401. That equates to approx. 2600 pounds per tire. This actually sounds a bit light but that's what I will go with.
Using a Tire Load Inflation Chart your tires should be inflated to about 50PSI to carry that 2600 pounds of weight.
An over inflated tire will heat up faster and higher than a properly inflated tire.

I would definitely double check your weights.

Mudchief · 05-18-2009, 05:39 AM

Glenn, the weight is correct we just went for a overnight stay. All of the tanks were empty except for the propane. I will weigh it at another CAT scale just to make sure. My concern is when we load it for a long trip it is going to weigh much more and the temperature will be much higher. This my have been happening with the Mission tires and I did not know it. I just always checked the tires for 80 pounds when they were cold and never checked when they were hot.

richfaa · 05-18-2009, 06:21 AM

I did note , via the pressure pro system, that the Missions (ST) ran a bit cooler that the LT tires we have on now. We have never seen a 90 on the ST or LT tires running at 80psi. Understand that it is normal for the pressure to rise when running due to heat.

dsprik · 05-18-2009, 06:43 AM

Dennis, this may not be an issue, but what was your ave hwy speed?

Mudchief · 05-18-2009, 02:22 PM

Dave my speed was between 60 and 65.

Mudchief · 05-18-2009, 02:31 PM

Glenn, today I looked at the new tires and they are marked with the same size as the old ones. However they are not as wide as the old ones. The spare which I have not changes out yet is about 5/8 to 3/4 inch wider. So much for China standards.

Art-n-Marge · 05-18-2009, 02:51 PM

LOL, this is not the first time I have heard that there is some concern when getting a new tool (the pressure monitor) and it is possibly showing you what is normal, but without the tool it was probably still the case.

At that speed (max speed rating for those tires is 65mph), and the weight you are carrying the tires should be able to take it even if they are more inflated. Checking the air pressure for that weight might allow you to drop the pressure and still satisfy their weight rating but it may still rise in pressure - after all the trailer weighs a lot more than your truck.

My understanding is that when tire weight rating and specifications are follow the specified air pressure is supposed to allow for natural temperature changes occurring during driving at any ambient temperature unless the tire specifies it cannot be used over or under a certain temperature. For example, if they say a rating at an air pressure, they would determine this under test conditions for heat and cold and the adjustment of the pressure in the tire will change accordingly but still be safe.

It just doesn't seem like it should be a problem if your tires are on the high side of inflation but well within the maximum recommended pressure to be problematic and you drive those speeds with the weight you tow, unless the tires are of poor quality. It's possible the tires run high. The tires should be able to take driving conditions as long as you are within spec.

I agree with dsprik, there may not be an issue. Take a few trips monitoring the pressure versus ambient air temperatures. You might find no difference at 80 or 100 degress outside.

As was explained by someone when I told them about my Mission problems, "How do you know when you are going to have a problem with Mission tires? You use them."

Finally, If the tires are supporting their weight and the air pressure is within spec what is the allowable maximum pressure allowance per outside temperature? I don't know, but how does the monitor know. Is that the default setting? For me if I keep tires within spec I would only be concerned with a tire that drops in pressure implying it is losing air, not increasing in pressure when using a tire monitor because of the weather. JMHO.

Art-n-Marge · 05-18-2009, 03:04 PM

I forgot to mention that the spare tire appearing larger is odd. You might want to actually measure with a tape measure. But if the stamped size of the tires are the same, then I would expect that at proper inflation they should measure the same, too.

You could actually measure the height of the spare tire and the installed tire, then the width of the tread and calculate for yourself if they are the same size. The smaller number on the tire size is the ratio of the height divided by the tread width. For example, 235/75 means the tire is 235 millmeters high and the tread width is 25% of the height (100% - 75% = 25%). The smaller the number the wider the tire.

Feel free to check it out.

bigmurf · 05-18-2009, 03:15 PM

Quote:

quote:Originally posted by Art-n-Marge

I forgot to mention that the spare tire appearing larger is odd. You might want to actually measure with a tape measure. But if the stamped size of the tires are the same, then I would expect that at proper inflation they should measure the same, too.

You could actually measure the height of the spare tire and the installed tire, then the width of the tread and calculate for yourself if they are the same size. The smaller number on the tire size is the ratio of the height divided by the tread width. For example, 235/75 means the tire is 235 millmeters high and the tread width is 25% of the height (100% - 75% = 25%). The smaller the number the wider the tire.

Feel free to check it out.

You sure about that?

firetrucker · 05-18-2009, 07:45 PM

Let's see, 25% of 235 mm is about 58 mm, which is a little more than 2 inches...shades of the model T. The tread width is 75% of the height, not 25%.

Bob

LonnieB · 05-19-2009, 03:24 AM

Quote:

quote:By Art-n-Marge
You could actually measure the height of the spare tire and the installed tire, then the width of the tread and calculate for yourself if they are the same size. The smaller number on the tire size is the ratio of the height divided by the tread width. For example, 235/75 means the tire is 235 millmeters high and the tread width is 25% of the height (100% - 75% = 25%). The smaller the number the wider the tire.

Feel free to check it out.

1. The first number in the sequence is the WIDTH in millimeters.
2. The second number is the sidewall aspect ratio which is a percentage of the width.
3. Add the aspect ratio multiplied by two to the wheel size to get the overall height.

Example for 235/80R16;
A. Convert mm to inches.
B. 235/25.4=9.25 Inches wide.
C. 9.25x80%=7.40 Inches per sidewall.
D. 7.40x2=14.8 Inches total both sidewalls.
E. 14.8+16=30.8 Inches total both sidewalls and wheel (overall diameter).

Feel free to check it out.

KTManiac · 05-19-2009, 06:24 AM

"...and so it is written."

You boys better pay attention to LonnieB, 'cause he's giving it to you straight!

Mudchief · 05-19-2009, 03:34 PM

I took the spare off and one of the new tires. Then put a straight edge across both sides and measured the distance and the old tire is 3/4 of a inch wider and the tread is 5/8 inch wider.

Lonnie, what do you think about the pressure I am seeing?

LonnieB · 05-19-2009, 05:05 PM

I think the pressure you are seeing sounds pretty high Dennis. I could see 6 to 8 psi increase, but 10 to 14? I am in agreement with Glenn, an overinflated tire will get hotter and get to higher pressures faster than a properly inflated tire. With your trailer only weighing 10401 pounds at the axles, with 80 psi, you are actually overinflating the tires for the load.
Is it enough to damage or shorten the life of the tires? I honestly don't know. I will agree with one thing Art-n-Marge said;

Quote:

quote:My understanding is that when tire weight rating and specifications are follow the specified air pressure is supposed to allow for natural temperature changes occurring during driving at any ambient temperature unless the tire specifies it cannot be used over or under a certain temperature. For example, if they say a rating at an air pressure, they would determine this under test conditions for heat and cold and the adjustment of the pressure in the tire will change accordingly but still be safe.

I know Rich, BirdingRVer, ole dude and several others keep a close eye on their tire pressure via a remote monitoring system and would have asked the same thing you did if they were seeing the increase you are seeing. Until you are loaded heavier, maybe lowering the pressure wouldn't be a bad idea.

Art-n-Marge · 05-19-2009, 10:12 PM

Thanks LonnieB... I had my ratio backwards, amongst other things.

But I am puzzled by some stuff and I hope you can clear this up.

I knew that low pressure could cause increased temperatures and that could cause premature tire failure - you can almost see these when you see someone by the side of the road and their tires running low pressure will eventually cause the side walls to fails. But I didn't realize that overinflation could cause overheating as well, as possibly indicated by the rise in air pressure by the tire monitor,. Even if you are within the maximum, is it true that overinflation will cause a problem?

I have read and been told by plenty of tire guys that you can cause either an uncomfortable rough ride or unusual wear in the center of the tread if overinflated for your application, as long as one does not exceed the maximum but this was with autos that are no where near the weight of our rigs.

I was taught that one should never exceed the maximum, but the maximum could be use and just be uncomfortable or cause bad wear in the center of the tire. Again, I was taught the rule of thumb is to use the recommended pressure as stated by the vehicle (sometimes this does not match your tire) and could make adjustments according to wear (outside or inside wear), but no higher than the maximum rating. How close is this to "Correctness"? What other rules apply?

My 4x4 F-250 states 75 lbs all around no matter what and this seems to be working great, loaded or not. Currently I have BF Goodrich's with over 45,000 miles and still going strong. I have had SUVs and minivans that stated a tire pressure when loaded, but when NOT loaded I could feel the vehicle bouncing all over the place and therefore ran lower pressure than stated (but over 35 to 50 lbs depending on the vehicle). Doing this I have had great success with all the tires on my minivans, vans, and trucks and using various tire brands (Michelin, BFGoodrich, Goodyear, Kelly, and Dunlop). Now for my cars, that's a whole different story but I will not go into that here.

MacDR50 · 05-20-2009, 05:39 AM

Some light reading. http://www.trailmastertrailers.com/p...are_safety.pdf
My own theory on many tire failures when attention to inflation is not an issue is simply road damage. I watched an otherwise very careful person haul his SOB over the edge of a curb leaving a gas station. For an instant one tire was suspended when the equalizer reached its maximum capacity. For that instant the other tire on that side was supporting the full weight of a 38 ft fiver on less than 50% of its normal ground contact. We inspected the tire to see if it showed any visible sign of damage but nada. He took it to the shop and they found signs of side belt seperation when they did an internal inspection. He was on his way on a 1500 mile trip. I bet he wouldn't have made it.

LonnieB · 05-20-2009, 01:08 PM

Art, that's a good question and I don't know if I can clear it up or not. I can't explain why an overinflated trailer tire heats up, I just know from experience that it happens. My THEORY is that the overinflated tire has less tread surface in contact with the pavement and all of the load is concentrated in a smaller area than the tire is designed for. In Mudchief's case, as I said earlier, I honestly don't know if the pressures he is seeing will damage or shorten the life of his tires.
When it comes to trucks I too go by the vehicle manufacturers recommendations on the door panel, but only for customers vehicles. On my 2003 F250 with LT265/75R16E tires I run 60 psi all around unless I am towing a trailer in which case I raise the rear to 80 psi but leave the front at 60 psi.
MacDR50, that is some interesting reading. Most of it I agree with, some of it I'm not sure about.

richfaa · 05-20-2009, 02:35 PM

We run our Coopper LT tires at 80psi as we did our missions. The coopers normally run at about 85/88 psi. The missions actually ran a couple of psi lower. I figure the increase is due to the tire heating up on the road. We have not weighed the 3400 alone for awhile but my best guess is around 13K. If I saw a 90psi on the pressure pro I would be concerned and suspect lowering pressure in that tire although not low enough to give an alarm.

We also note a 2psi difference (cold reading) Example 80 at the tire with a good digital gage will read 78 at the monitor in the truck.

Art-n-Marge · 05-20-2009, 08:13 PM

Here's a thought. Maybe the questions on how high the allowed pressure should be could be sent to the respective manufacturer for an explanation.

Maybe an informal poll within the MOC that asks, "For your rig combination what does your Tire monitor say when driving down the road"? While there are so many factors that can affect the air pressure, let's just find out if anyone gets 10-15 over what the tires were inflated to. With past tire problems I've had I will be getting one of these units, but being as cautious as I am, I'm sure I'll get nervous seeing some high numbers unless other members have posted in kind.

Any of you tire monitor owners want to create the forum topic? I don't have a tire monitor and won't have anything to report, but will be very interested in the results.

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