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Old 11-04-2015, 12:38 PM   #91
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Im not intentionally trying to stir the pot (troll) here but by this same logic wouldn't all these forces make the axle rating not high enough to handle the trailer. If I add in the wind force and down force of a turn aren't my/your axles overloaded now? What about the frame too? Doesn't the newly calculated stresses put the frame out of spec?

We are in the realm of calculating all these forces to stay within weight so the weight police dont pull us over and ticket us or we fear that pulling this thing down the road is like a nuke waiting to go ff. I think all this is unnecessary in real world application. Basically slap some higher load rating tires on your trailer (like the hundreds of other campers out there) and stay under GVWR and go out and enjoy camping.

It seems like I could do hundreds of calculations to say something is out of spec, something is obviously working because I see hundreds of campers being pulled down the road daily.

The fact of the matter is the RV business is just that, a "business". The definition of a business is an establishment to make money through commerce. If manufacturers were to put top of the line tires that built in a safety margin and put upgraded axles on and then beef up the frame that cost has to be absorbed somewhere and that somewhere would be the consumers wallet. Based on all the threads on here that ask how to negotiate and find the good deal, as well as when the best time of year to get the cheapest price I don't think the average consumer would want to do that. In addition that is why there are levels of campers, Entry level all the way to 500k dollar top of the line untis.

I am not saying that this is a perfect business or practice but it is a reality. Look at the auto industry... you get trucks that have P rated tires and so forth.

I apologize for the rant but I think at times we get so lost in the "what ifs" we all miss the enjoyment of getting out there and LIVING LIFE.
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Old 11-04-2015, 01:15 PM   #92
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Originally Posted by SuicideSaints View Post
Im not intentionally trying to stir the pot (troll) here but by this same logic wouldn't all these forces make the axle rating not high enough to handle the trailer. If I add in the wind force and down force of a turn aren't my/your axles overloaded now? What about the frame too? Doesn't the newly calculated stresses put the frame out of spec?

We are in the realm of calculating all these forces to stay within weight so the weight police dont pull us over and ticket us or we fear that pulling this thing down the road is like a nuke waiting to go ff. I think all this is unnecessary in real world application. Basically slap some higher load rating tires on your trailer (like the hundreds of other campers out there) and stay under GVWR and go out and enjoy camping.

It seems like I could do hundreds of calculations to say something is out of spec, something is obviously working because I see hundreds of campers being pulled down the road daily.

The fact of the matter is the RV business is just that, a "business". The definition of a business is an establishment to make money through commerce. If manufacturers were to put top of the line tires that built in a safety margin and put upgraded axles on and then beef up the frame that cost has to be absorbed somewhere and that somewhere would be the consumers wallet. Based on all the threads on here that ask how to negotiate and find the good deal, as well as when the best time of year to get the cheapest price I don't think the average consumer would want to do that. In addition that is why there are levels of campers, Entry level all the way to 500k dollar top of the line untis.

I am not saying that this is a perfect business or practice but it is a reality. Look at the auto industry... you get trucks that have P rated tires and so forth.

I apologize for the rant but I think at times we get so lost in the "what ifs" we all miss the enjoyment of getting out there and LIVING LIFE.
I understand your point. IMO the problem with the "Quality costs too much" thought process is what almost put "Detroit" out of business when Toyota & Honda etc entered the US market. The consumer decided they wanted better quality.

But given the growth of Walmart and cheap imports being bought by American workers who at the same time complain about their jobs being shipped overseas. One has to wonder if the average person has any concept of the cost of poor quality.
This cost shows up in a majority of RV forum complaints about the failure of not just tires but of refrigerators catching fire or slide-outs that don't or any of the numerous other component failures. I don't buy the argument that owning an RV is like dragging your house down the road.
If car makers can design and build 12v systems that they can warranty for 10/100,000 why can RV companies only manage to get their 12v systems to only last 12 months and a couple thousand miles?

Why do tires on motorhomes last 7 to 10 years but only 3 - 5 on TT? Could it be that a good portion of the tires selection is done by companies such as Ford or Freightliner or GM?

The purpose of this particular thread was to offer a possible reason for the short life and high failure rate of tires in RV use. If tires are selected that only have a safety margin of 50# but the RV is built with a 300# bias to one side then you add another 100 to 400# bias due to wind you end up with some tires being overloaded by 30% or more, and people are suppose to accept this?

If so I suggest we stop letting people complain about tires and just explain that they got what they wanted, a cheaper RV.

Just like hand tools. I don't expect S_K or Craftsman quality from Harbor Freight and I certainly don't complain when a HF tool fails early.
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Old 11-04-2015, 01:27 PM   #93
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OKI Marine,

Slowing down won't help in crosswind. If there is a high wind advisory, definitely stay off the road.


And if there's zero margin between the load on the tires and their load rating, you can't win. There's no way to avoid overloading them when moving. You can't avoid turning, and you can't avoid wind.

My overload occurs with the factory tires. I've replaced them with Kumho 857's that have a much higher load rating. Old tires are 1760lbs; new tires are 2270lbs. The slightly larger diameter worries me, but isn't a problem based on a consensus that includes a trailer dealer. When I try my math with my new tires, the overloads for both wind and curves for the most part go away. If I don't use my full GVWR, then the math looks even better.




So, all the advice I've seen to change from LRC to name brand LRD tires seems good to me. This certainly helps. Each trailer will be different, so to know for sure one needs to do the math for his set of trailer and tires.

The Carlisle Tire recommendation for a 20% margin between trailer weight (including tongue) and combined load rating of the tires seems also to be good advice. This does a good job of eliminating the overloads in reasonable conditions, both on curves and in wind based on my math.




Warning: if you use tires other than those on the vehicle rating plate, you may void your warranty and create other problems. For me, this is the lesser of evils.




The underlying problem is created by the manufacturers, IMHO. I think it's reasonable to expect that factory tires on a fully loaded new trailer should not be overloaded in normal driving conditions like turns taken at the advisory speed (which most people seem to exceed), and winds that don't trigger a high wind advisory. So I think the manufacturers have a serious problem, and possibly a product liability issue, to deal with.
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Old 11-04-2015, 01:31 PM   #94
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Given the Rv warranty is probably only 12 months and your TT tire warranty may be shorter why worry about that warranty? Especially since they will not stand behind most tire failures.
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Old 11-04-2015, 01:37 PM   #95
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I don't see any benefit in the discussion. People can do all the calculations they want and it still isn't going to change the rv industry. Engineers have calculated that a humming bird can't fly, but it still flies.
What will change the RV industry, as Tireman suggested previously, is educating people about the problems and motivating them to report safety issues to the NHTSA.

I have done this. I've provided my math to the NHTSA and they have agreed to take a look at it. My impression is that they're serious about it. It would certainly help if others also do this, while being careful that any complaints have substance.
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Old 11-04-2015, 01:49 PM   #96
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Originally Posted by Tireman9 View Post
I understand your point. IMO the problem with the "Quality costs too much" thought process is what almost put "Detroit" out of business when Toyota & Honda etc entered the US market. The consumer decided they wanted better quality.

But given the growth of Walmart and cheap imports being bought by American workers who at the same time complain about their jobs being shipped overseas. One has to wonder if the average person has any concept of the cost of poor quality.
This cost shows up in a majority of RV forum complaints about the failure of not just tires but of refrigerators catching fire or slide-outs that don't or any of the numerous other component failures. I don't buy the argument that owning an RV is like dragging your house down the road.
If car makers can design and build 12v systems that they can warranty for 10/100,000 why can RV companies only manage to get their 12v systems to only last 12 months and a couple thousand miles?

Why do tires on motorhomes last 7 to 10 years but only 3 - 5 on TT? Could it be that a good portion of the tires selection is done by companies such as Ford or Freightliner or GM?

The purpose of this particular thread was to offer a possible reason for the short life and high failure rate of tires in RV use. If tires are selected that only have a safety margin of 50# but the RV is built with a 300# bias to one side then you add another 100 to 400# bias due to wind you end up with some tires being overloaded by 30% or more, and people are suppose to accept this?

If so I suggest we stop letting people complain about tires and just explain that they got what they wanted, a cheaper RV.

Just like hand tools. I don't expect S_K or Craftsman quality from Harbor Freight and I certainly don't complain when a HF tool fails early.
I understand the point of the thread and I understand what you are saying, I am just saying that this is a known problem and the only current solution is either roll the maxxed/cheap tires till they fail, negotiate at the time of sale for better tires or drive straight to your shop of choice and get new ones with a higher load rating.

A caveat though which is my main point.....

By the OPs own admission and math, his current tires (at the time of failure) were rated for 1760 each. The trailer is 7700#s - TW (700#s) divide that by 4 tires = 1750 per tire. This is within spec for static.

Now add in 500# of force for dynamic (turns) and add in 400#s for wind force. So that makes the load on the tire 1750 + 500 + 400 = 2650.

In addition to that 2650 it was stated that you "should" have a 20% margin of safety. 2650 + 20% = 3180 to have all my bases covered. Or even if you do 20% safety on the original 1750 tire that still isn't enough.

So this thread would lead me to believe that I need tires that can hold a minimum of 2650 lbs to 3180 pounds (for a 7k# TT) depending on the dynamics and "recommended" safety margin. That is at the top of the range for D tires almost to E tires.

I just dont buy it.......
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Old 11-04-2015, 01:59 PM   #97
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Originally Posted by Gyrogearloose View Post

My overload occurs with the factory tires. I've replaced them with Kumho 857's that have a much higher load rating. Old tires are 1760lbs; new tires are 2270lbs. The slightly larger diameter worries me, but isn't a problem based on a consensus that includes a trailer dealer. When I try my math with my new tires, the overloads for both wind and curves for the most part go away. If I don't use my full GVWR, then the math looks even better.
By your own admission and math, in a dynamic state of turn and wind you would need a minimum of 2650# capacity on each tire, even more capacity if you want a safety margin bigger than anticipated turn and wind. So those new tires are still overloaded by 400#s.

I hope you are seeing my point about just getting out there and living/enjoying life......
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Old 11-04-2015, 02:09 PM   #98
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By your own admission and math, in a dynamic state of turn and wind you would need a minimum of 2650# capacity on each tire, even more capacity if you want a safety margin bigger than anticipated turn and wind. So those new tires are still overloaded by 400#s.

I hope you are seeing my point about just getting out there and living/enjoying life......
I've got a little over 40 years of experience designing products. This problem of worst case calculations comes up all the time.

Yup. If you take the worst case of multiple bad things happening all at the same time, and then try to design a product that survives, you will usually end up with something that you can't sell because it's too complex, or heavy, or expensive.

But this doesn't mean that a product shouldn't handle individual and reasonable stresses. Good designs will handle some simultaneous stresses, but not necessarily all possible combinations.

For me, having had an unexplained tire failure on a winding road, and having discovered that my tires are likely to be overloaded by hundreds of pounds when I tow on curves, doing nothing is not an option. My new tires should handle curves or wind, and if it's windy and curvy at the same time I'll slow down to reduce at least the portion of the load due to the curves. This is the best solution I can think of for my situation.
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Old 11-04-2015, 02:51 PM   #99
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The site team cleaned this one up somewhat. Any posts that were condescending, off-topic, or not that faintest bit relevant to the ongoing discussion were removed, and will continue to be removed.

If this topic isn't something you can contribute to, then please find one that you can. It is trolling and a disruption to forum harmony for those who want to interject themselves into a thread, just to state they don't feel the thread is relevant.

It has been a good discussion and the site team will make sure it continues as well as it's been.
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Old 11-05-2015, 11:56 AM   #100
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Do all of the math you like. The only thing that matters is if your trailer came with 'C's and they are close to being maxed out, change them out with 'D's. It is really just that simple.


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