Towing on Extremely Hot Days

[Walt523]

Just an FYI for st tires from a large oem manufacturer
https://www.maxxis.com/trailer/trail...nflation-chart

Btw I did the same with my 5th wheel and TT. Again look at the manufacture recommendations on loads and psi. The point is that you don’t need max psi for all loads, some times you do because rv makers max out tires and axles. But EVERYONE at some point exceeds the 65 mph max speed.

Under MAX PSI is not under inflation for many tires, TT tires and 5th tires. See above linked chart.

Often MAX psi is recommended, because people don’t actually know this load being carried and recomending MAX PSI leaves out the problem of people just guessing. Like I said most people don’t even weigh their campers.

[LarryW]

Walt, the Maxxis chart clearly shows how inflation to the maximum recommended psi makes the tire capable of its maximum load. It also decreases flex which decreases temperature.

[LarryW]

“But EVERYONE at some point exceeds the 65 mph max speed.”

Walt, while my current TT tires are rated for 81 mph, I never exceed 65, ever. Rarely hit 60. Speed limit in California for vehicles towing is 55. I support this statute. Drive behind me sometime, you’ll see.

[old_engineer]

Stop with the bad advice on tire pressures. Trailer tire manufacturers have charts that provide the inflation pressure based on load. They do not say run them up to the maximum pressure on the side wall as that can be just as dangerous as under inflating. An overinflated tire for the load will put less tread on the road and make it more susceptible to blowouts from impacts such as potholes. Again here are two chart that contain information for ST tires. One from Goodyear and the other from Maxxis both clearly show lower inflation values for lower weight loads.



https://www.goodyearrvtires.com/pdfs/rv_inflation.pdf


https://www.maxxis.com/trailer/trail...nflation-chart

[Walt523]

Originally Posted by old_engineer

Stop with the bad advice on tire pressures. Trailer tire manufacturers have charts that provide the inflation pressure based on load. They do not say run them up to the maximum pressure on the side wall as that can be just as dangerous as under inflating. An overinflated tire for the load will put less tread on the road and make it more susceptible to blowouts from impacts such as potholes. Again here are two chart that contain information for ST tires. One from Goodyear and the other from Maxxis both clearly show lower inflation values for lower weight loads.



https://www.goodyearrvtires.com/pdfs/rv_inflation.pdf


https://www.maxxis.com/trailer/trail...nflation-chart

EXACTLY, Old Engineer. The problem is lack of education on tires and why so many people have blow outs.

The problem is for so many years everyone filled their tires to the max pressure stated on the tires. THAT’S A MAX pressure, not a min pressure . They also list the MAX load. They think that if you’re under max PSI, you’re under inflated. Old habits die hard.

For my 5th wheel tires the min PSI was 35 psi and max was 80 psi, for my motorhome the max psi is 110 and min is 70 psi. Those are MANUFACTURE recommendations for psi based on loads. SO I don’t know who came up with that they will only recommend max PSI, That’s simply not true.

A blow out can do many thousands of dollars of damage and SO many people don’t even have tire pressure monitors when they travel. I monitor tire pressure as well as temps of my tires.

I can tell you running tires at max pressure will give you some scary tire pressures. Tires also have an over pressure threshold, which you can reach when filling to max pressure while running at max PSI, max loads and high temps.. There is a reason they build in over pressure warnings into tire pressure monitoring systems.

It’s a lot of fun to watch 5th wheels, TT’s and motorhomes gettting weight at a rally and seeing how many people drive around grossly over weighted , old tires, unbalanced loads and the puzzled look on their faces when asked if they know the CCC on the camper. Clearly there is a gross lack of tire pressure and loading knowledge on this thread.

Tire manufactures put out the tire inflation and load charts for a reason, USE THEM.

[Walt523]

Originally Posted by LarryW

Walt, the Maxxis chart clearly shows how inflation to the maximum recommended psi makes the tire capable of its maximum load. It also decreases flex which decreases temperature.

Larry simple not true. You lose no capiblity when inflating to the manufactures recomended PSI for the weight it’s carrying. If you’re carrying max load then inflate to max PSI.

In addtion as the tires heat up their load handling capabilities increase. Do you even know how much weight you’re carrying? On really hot days my campers’s PSI will rise above the PSI for max load. SO, My cold pressure was slightly above the recomended psi for my load and then as I drive it increases at times to the max psi.

All tires flex as they are part of your suspension system. After watching my tire pressure monitoring system and checking them with a laser temp sensor for MANY years on various different campers I can tell PSI had no real bearing on tire temps. Road temps and ambient temps had the most affect on tire temps.

You need to go to a tire seminar and learn about tires and tire PSI.

[LarryW]

Thank you for supplying your different, opposing views.

[Walt523]

Not my opinion, tire manufacture recommendations and based on the load charts they provide.

[Winniehurn]

Is your Tundra equipped with optional tow package (additional transmission cooling, etc.)? If so and with decent maintenance as you note above, I doubt you will have any overheating issues towing a Micro Minnie. You will be well below the rated maximum towing load for your Tundra. You probably bought a Tundra for same reason I did.... one tough, well engineered truck within specification ratings! Go with confidence.

[bigb]

RV tire safety can be a complex subject. I have been studying Roger Marble's "RV Tire Safety" blog for about a month now, extremely good information written by a retired tire engineer with 40 years in tire development and design. Roger taught classes to engineers at DOT and to over 300 engineers in the tire and car industries. I urge anyone to study his blog, you can't get better information if you paid for it. This information could save you from a catastrophic failure someday. Here is a link to one of his articles about travel trailer tire inflation and I copied the summary paragraph for those who foolishly do not wish to visit his blog.

RV Tire Safety: Tire inflation not the same for all trailers

[LarryW]

bigb, thank you for posting. I note this quote: “BUT for Tandem and triple axle trailers I strongly recommend that the tire cold inflation be set to the inflation molded on the tire sidewall associated with the tire maximum load capacity.”

[Walt523]

Larry you’re the typical hard headed guy, who gets posted all the manufactures recommendations , but ignores it.

There is a reason why people recommend max psi and it comes down to people don’t weigh their loads. The next line starts with also loading these tires to 85% of the max. Again, have you weight your camper? You haven’t answer your weight and that’s where tire inflation starts.

First you need to know how much you’re going to carry, which most people don’t. The blogs recommendation of adding a safety margin is sound and is what I do, because you’re load is always changing.

Many campers are manfacured to the load limits, some are not. Some are loaded to max or excessively by their owners.

Again it comes down to load. For those in the know it’s been common practice to weigh your camper fully loaded. Which included people, gear, fuel, etc. Load balancing is also part of the equation as many campers are loaded incorrectly. That’s where four cornering weighing comes in. At most scales you can only do side to side and not four corners, but it will help you with load balancing. Have you even ever done that or just blindly loading your camper and putting in max psi?

In our 5th we traveled light for many years and had 2000lbs of CCC left over. So there was no reason to inflated to max psi or even close. Not every situation is the same and it starts first with knowing your load fully loaded. Then go onto tire PSI recomended by the manufacture.

Blanket PSI recomendations are just wrong, but I understand why people do it, they are simple and people are dumb. That way you don’t subject yourself to liability.

Notice the difference between me and you. I say load you camper, weigh it and then determine the PSI based on tire manufactures recommendation. Your recommendation is MAX PSI for everyone.

IF you were really concerned on safety you’d be concerned why manufactures max or exceed axle loads routinely. Ever wonder why a 5th wheel (they do it with TT’s Also)with 14k max weight comes with 6k axles? I’ll give you the quick answer, first it’s cost , then they depend on your truck to carry some of the weight. But if you unbalance your load your axles are over loaded.

How many replace both same side tires after a flat or blow out? Hardly any, but if you realized that ones you have a flat or blow out the other tire is grossly overloaded and damaged, then you’d understand why people have multiple blow outs on a same trip are so common.

[LarryW]

Well, at least we found one subject where we agree but no need to assume I didn’t understand the dual replacement theory:

“How many replace both same side tires after a flat or blow out? Hardly any, but if you realized that ones you have a flat or blow out the other tire is grossly overloaded and damaged, then you’d understand why people have multiple blow outs on a same trip are so common.”

[bigb]

Originally Posted by Walt523

There is a reason why people recommend max psi and it comes down to people don’t weigh their loads.
.

Walt, when talking about motor vehicles and single axle trailers I tend to agree with you, it is best for the general public that does no research to stick with full inflation. Those who do their due diligence can do otherwise but you and I both know that is the minority.
But for trailers with more than one axle there is another reason max PSI is recommended for everyone, Interply Shear. It is all fully explained on Roger's blog.

[LarryW]

bigb, please note the Carlisle warranty at https://www.carlstargroup.com/Portal...y-Warranty.pdf

“This Warranty is void if the tire:
• is worn past the last 3/32 of tread depth at any point on the tread contact surface • is run while it is flat or underinflated...”

And “Carlisle ST FAQ
What is the proper tire inflation?
Maintain air pressure at the maximum PSI recommended on the tire sidewall. It's best to check tire pressure with a quality tire gauge when tires are cold and in the shade. Under inflation is the number one cause of trailer tire failure. An underinflated tire creates abnormal tire flexing and excessive heat causing...”

[bigb]

I'm with you on that Larry, but for instance on my F-350 there's no way I run 80 PSI (sidewall label) when unloaded. The factory door sticker says 55 front and 80 rear, my front axle weighs 5,080 (diesel) and rear is 3,780 unloaded except for camper shell and tools. I run 62 front and 55 rear at those weights which is from the load and inflation tables for my tires plus 10%. Tandem & triple axle trailers however need max inflation to minimize damage from interply shear according to Roger Marble who's advice I hold in high regard. If I ever put 2 tons of gravel back there I will go with 80.

[LarryW]

I was only speaking of trailer tires. On trucks I agree...adjust them.

[Walt523]

Larry, what you’re not understanding is that manufacturers want the tires to run with all treads in contact with the roadway. This needs the tire PSI to be adjusted to the load they are carrying.

Now for many campers, since they manfacture many to be at max limits on everything then you run max PSI. Weighing your camper will tell you when to run them at max PSI, which could be the case for many.

Now if you ask a manfacturer for a single PSI, they will tell you MAX PSI. Why would they say this, well they can’t give you a PSI for your camper without knowing the load and there are 100’s of thousands of campers on the road, so you get the answer Max PSI. IF you ask them if the tire PSI can be adjusted for load, they will say yes. When I had my tires rotated and balance at the Michelle dealers he never put in max PSI, they always asked what PSI I run at.

Now since they want the tire to run with full contact on the road, let’s try to get you to understand it this way.

Let’s say my Max PSI is 50psi for a max load bearing weight of 4K pounds. But, let’s also say my camper is empty and only weight 2K pounds. At this point your tires would be over inflated and crowning, with only the middle portion touch the roadway. This caused uneven tire wear and bouncing , which is dangerous.

You have to lower the tire PSI to get the tire in full contact with the roadway.

Now if my tires are inflated lower then max and within the manfacturer PSI for that load they are are NOT under inflated. You seem to be stuck if they are under MAX PSI they are some how under inflated and that’a simply not true.

I can tell you after speaking with many Michellin reps(since I only run Michellin on all my campers), they do not agree with Rogers, Max PSI recommendation for every camper. But they do think it’s a catch all for the masses. Spend some time speaking with them and ask pointed questions and you’ll get a different answer then the one size fits all. You run want you want, I run what the manufactures recommend and have never had a blow out or tire issue.

If tire manufacturers wanted you to run your ST tires only at max PSI, then they wouldnt put out PSI reconditions / load charts. Those charts are put out for a reason. It would be much simpler just to say MAX PSI and not do the development and testing for those charts.

Here is an interesting manufacturers recommendation for my ST tires on my tow dolly. Loaded 50 PSI, unloaded 10 PSI. Under your theory I should be running them at max PSI.

[Fasttimes]

"Larry you’re the typical hard headed guy, who gets posted all the manufactures recommendations , but ignores it."


Walt, you're the typical know it all guy who thinks they are right and everyone else is wrong. Chill out with the attacks on people, this is not what we come here for. It's great that you believe you are all knowing in tire knowledge, but the truth of the matter is it is you OPINION.



"Opinions are like [moderator edit], everyone has one."

[old_engineer]

Originally Posted by bigb

RV tire safety can be a complex subject. I have been studying Roger Marble's "RV Tire Safety" blog for about a month now, extremely good information written by a retired tire engineer with 40 years in tire development and design. Roger taught classes to engineers at DOT and to over 300 engineers in the tire and car industries. I urge anyone to study his blog, you can't get better information if you paid for it. This information could save you from a catastrophic failure someday. Here is a link to one of his articles about travel trailer tire inflation and I copied the summary paragraph for those who foolishly do not wish to visit his blog.

RV Tire Safety: Tire inflation not the same for all trailers

If you take this in context with other stuff he has written this is the quick answer because he does not believe the typical RV owner has the knowledge nor is capable of figuring this out correctly.



I also noticed he contradicts himself in regards to motorhomes, single axle trailers and multiple axle trailers. His rationale for the quick answer on multiple axle trailers is the individual tire weights are not necessarily equal where he says not to inflate using weight charts. Different tire load weights could be true for RV's and single axle trailers as well so why the different responses? If there is that dramatic of a difference in tire loads the trailer would not track correctly no matter what you did. It is a matter of basic physics.I'm also a bit bothered by him stating that he once measured a 5th wheel straight from the factory where one tire was already overloaded by I think 27% and using it as part of the rationale for his quick answer. That would never had made it out of the prototype stage due to product liability issues or it was a major manufacturing mistake which would be a warranty/liability issue regardless of when it occurred. The full context is missing as to what was the cause of the discrepancy so really shouldn't be used as part of an argument.



Also in his blog and in some RV forum updates he tells people asking about setting tire pressure to weight that they have all of the needed information and should be able to finish the math themselves. He does not tell them to use the maximum PSI. There are other instances where someone has a higher load range tire than original. He tells them it is ok to use the same tire pressure from the trailer inflation label and not to worry about going to maximum inflation as long as it is within the spec of the manufacturers tire load tables. However more than once he makes reference to using manufacturer tire load tables and if you cannot find them, like on some private brand tires, use the side wall. Again this is an exception and a quick answer.



The author's real thrust is tire failure is rarely caused by a defect in the tire itself. It is most commonly caused by people who do not check their tire pressures on a regular basis and overloaded trailers. I feel the second case is actually the more common cause with how few people actually weigh. To further this I have read many posts on different forums where people are surprised they are 400, 500 or 600 lbs overweight when they finally hit a scale. You then have the people who have weighed, know they're overweight "but not by much so it's ok" who then complain when they blow a tire or break an axle. I'm not one that believes the typical trailer owner needs to weigh frequently but you need to do it at least once if you are relatively consistent on what you pack. If you full time or vary how/what you pack a lot then more frequent weighing are in order.



My last thoughts are a lot of this back and forth on tire pressures is hold over from bias ply days. For a long time it was felt that radial tires should not be used on trailers due to side wall differences. The higher stiffer sidewalls of the bias ply were thought to handle the lateral forces generated by the trailer better. This stiffness also made tire pressure less of an issue on how much tread was on the road. However much like the old radial tire rotation misunderstanding it turns our radials are fine on trailers and give the trailer better traction. This change occurred when it was determined that it isn't so much the sidewall carrying the load but the air inside the tire itself. Radial do have one major difference and that is how the tread meets the road is much more dependent on tire pressure. Being over or under will put less tread on the road and in the case of under inflation potentially sidewall. This makes the weight loading in relation to pressure all the more important than it was with bias ply.



An interesting side note for thought. I was reading a paper from John Deere and the Alberta Farm Machinery Research Center about tractor tire inflation pressures. It is in regards to radial tractor tires but is all about tire load and pressures. They found most farmers overinflated their tires and when lowered into the proper range for the actual tire weight load traction efficiencies went up 4%-7%.