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Old 10-27-2015, 10:34 PM   #11
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Gyrogearloose, I had a feeling you would be on top of this, thanks for sharing. That was something I had not considered. If you hear anything further, we'd really like to hear it.

Well, Michelin does make a 15" LT tire, but I'll have to check to see what the load rating is.

Thanks again.

Deb
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Old 10-28-2015, 09:05 AM   #12
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Quote:
Originally Posted by SuicideSaints View Post
The tires are rated to carry the full TT because you subtract TW since that part is carried by the TV. This makes them "within" limits.
......
The load range on the sidewall is for static measurement and not meant to be calculated for dynamic applications.

I'm not so sure the tire manufacturers agree with this.

Carlisle Tire has a document titled "Trailer Tires: Tips & Best Practices". In that document they give the following advice:
"The combined capacity of the tires should exceed the loaded trailer weight by 20 percent."
There is no mention of subtracting tongue weight, which adds another 10%.

The net result of this recommendation is that tires should have about 30% more capacity than the ones put on my trailer by FR.

The reason for this excess capacity would be because the static load rating of tires doesn't have margin for lumps, bumps, and weight transfer on curves. The overloads that I calculate on turns just about go away if the advice from Carlisle Tire is followed.

I'm trying to contact an engineer at Carlisle to probe this further....
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Old 10-28-2015, 09:27 AM   #13
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Gyro,I/We knew that our O/E Tires were Questionable so we Called our Tire Dealer and placed a order for Maxxis 8008 15" Tires! They were installed and down the road we go! Good Luck on your Quest for Tires! Youroo!!
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Old 10-28-2015, 09:52 AM   #14
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Thanks, youroo!

I've changed my tires to Kumho 857 trailer tires and raised the load rating to where it ought to be. In the process I made a new mistake. The Kumho's are size 205R14. I asked for 205/75R14 as recommended for my trailer. The new tires are 0.9" larger in diameter than I expected, which was not my intent. I'm now trying to figure out if this did any harm. The gap between the two tires was already small, and got smaller. This is my new concern.


Otherwise, I'm trying to raise awareness of the tire problem on trailers. It doesn't make sense that we all should buy a new trailer and immediately go out and buy new tires. And it doesn't make sense that the large number of reports of tire failures in RVs should be written off as pilot error by owners. This wouldn't be tolerated in cars owned by the same people...or by the NHTSA.


A friend of mine would call what I'm doing 'Tilting at Windmills'. Maybe this is futile; maybe not. :-)
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Old 10-28-2015, 01:13 PM   #15
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Well, I heard back from Dexter on two questions:


I asked whether the 0.9" larger diameter of my Kumho 205R14s would cause any problem with the axle or spindle. The answer was no. This makes me suspicious that the earlier warning I received from a Dexter engineer concerning increasing the tire diameter may have been a little overly conservative. I suggest going to the Dexter website and use their tool to ask similar questions.


I also asked whether overloading of the axles due to weight shift on curves might be a problem. Technically, this doesn't exceed the axle rating because as weight gets added to one end of the axle, it comes off the other end. The answer to this was also 'no'. I was told that the axles have extra capacity to handle this kind of overload. This begs the question 'how much extra capacity?'


So at the moment, my slightly bigger tires aren't a problem for the axles, and I can take curves without worrying about axle failure.


I'm still trying to get a response from credible tire manufacturers about whether a 580lb overload on curves is ok.
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Old 10-28-2015, 01:40 PM   #16
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Thanks so much for sharing this info. Getting all of this "right" is so crucial, and when it's done, makes traveling and camping so much more enjoyable!

Deb
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Old 10-28-2015, 02:34 PM   #17
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To Replace my 205/75 R14 tires with something reasonable, I found Taskmaster tires at etrailer.com that are rated for 81 mph and Load range D. I had to go to 215/75 R14s. They are about 1/2" larger diameter. I've been on one trip, and no problem so far. There is no excuse for tires that blow up, but Firestone got away with it for years until someone noticed it was killing people. In the Forest Service, we doubled the axle rating for dirt road use. Rough roads will overload an axle in a hurry. I broke the axle off my hunting trailer that way. If you boondock like we do, you'll want to take it very slow.
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Old 10-28-2015, 03:22 PM   #18
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Yup. I also had my eye on the Taskmaster 215/75R14 LRD.
2200lbs @ 65psi sounds a lot better than 1760lbs for the factory tire.
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Old 10-28-2015, 03:26 PM   #19
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I just received an email from an engineer at NHTSA.
I had sent them the analysis I did on my tire loading.
She's asking for the details of my trailer and tires...photos of the rating labels, of the trailer itself, and the like.


Hopefully this mess will soon be cleared up....
Stay tuned....
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Old 10-28-2015, 03:39 PM   #20
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Quote:
Originally Posted by Gyrogearloose View Post
Well, I heard back from Dexter on two questions:


I asked whether the 0.9" larger diameter of my Kumho 205R14s would cause any problem with the axle or spindle. The answer was no. This makes me suspicious that the earlier warning I received from a Dexter engineer concerning increasing the tire diameter may have been a little overly conservative. I suggest going to the Dexter website and use their tool to ask similar questions.


I also asked whether overloading of the axles due to weight shift on curves might be a problem. Technically, this doesn't exceed the axle rating because as weight gets added to one end of the axle, it comes off the other end. The answer to this was also 'no'. I was told that the axles have extra capacity to handle this kind of overload. This begs the question 'how much extra capacity?'


So at the moment, my slightly bigger tires aren't a problem for the axles, and I can take curves without worrying about axle failure.


I'm still trying to get a response from credible tire manufacturers about whether a 580lb overload on curves is ok.

Just remember that's .45 per side. So you really only added .45 to the bottom. I assume you actually measured the tire. Specs could be a hair off depending on how you measure. May have to break out the geometry and use circumference and 3.142


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