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Old 09-12-2016, 11:30 AM   #29
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Airstream will sell whatever wheels/tires customers demand in the marketplace. It's called marketing. Airstream also refuses to warranty any damage caused by tire failures. That is the tire mfr'r and customer's responsibility.
This has always brought up semi-heated arguments because individual choices are owned by those individuals who feel they must defend their choice. However, if one will read the many responses on this subject, one will come to the realization there is no standard (control group) to which one might legitimately judge the best practice.

"I use XX psi and it tows like a dream." Of COURSE it does! It's a well-designed trailer. It will tow like a dream until that tire blows!

So many use 35/65/70/or-whatever suits-and-satisfies their imaginary theories that no sense can be made of it, and no mandatory reporting or recipient of the nonexistent reports has been designated to collect the data. I.E., there is NO DATA...because none of the user-group participates in any form of testing to which the tire industry rigorously subjects their products over decades of experience. The only reliable experience comes from the tire industry who designs, builds, and carries the liability of defective product, and who universally recommends max sidewall pressures for trailers. Why? Because that is the strongest, most failure-resistant condition at which the tire may be operated which will also provide the most sway-resistance.
Tread-wear? Not a problem with the vast majority of trailers anyway, because they chronologically should be changed-out long before most owners can wear out the tread.
The most damaging condition a tire can suffer is underinflation.

BTW, any tire running pressure at/above 65 should have metal valve stems. So should any off-pavement or other severe-service operation. Rubber, pull-through stems are not designed for high-pressure severe-service.

Here we are, living the most advanced state of technology ever achieved and otherwise literate people ignore the only source of reliable data on the subject, the trailer and trailer-tire and rubber manufacturers.
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Old 09-12-2016, 12:17 PM   #30
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Originally Posted by Rocinante View Post
I'm with you, but it's his shop and he can do what he likes there.

I will also say that after the scary experience we had setting our previous GYM ST tires to 65 cold and then running them thru the Mojave, we would never do that again.

As others have noted above, we use the Michelin-provided load tables for the tire featured in this thread to determine our optimal cold pressure. We'll trust Michelin's load tables over any opinions presented here, thanks.
Hey, I'm not telling anybody what to do, just relaying my digestion of all that has been previously discussed, so we don't have to go down that road again. I do trust the info provided by both tire engineers who have participated in the past.
I certainly understand RichS25's right and responsibility to pay attention to tire manufacturers and his own liability concerns. I live those every day, but sometimes a re-review is in order, so as not to lose business.

My determination of proper pressures, for me, are a culmination of digesting all the material here, my experience and formal education and training, and specific to my weights.
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Old 09-12-2016, 01:23 PM   #31
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I run 80 psi due to the weight of my 30' slide out. Keep in mind that the maximum pressure rating for your tires does not need adjustment for weather. So in hot weather the tires can safely run above the 80 psi mark but still be within design pressure limits. So the only adjustments I make is air addition as we get into the colder days to get the tires back to 80 psi. I might reduce pressure if it goes above 80 psi, but that is when the tires are cold and before the light of day.

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Old 09-12-2016, 04:45 PM   #32
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Originally Posted by Boxite View Post
Here we are, living the most advanced state of technology ever achieved and otherwise literate people ignore the only source of reliable data on the subject, the trailer and trailer-tire and rubber manufacturers.
Yer kinda forgetting the load tables mentioned above, cited here again for reference: http://www.michelintruck.com/assets/...k_Sept2011.pdf

See page 11 and page 25.

At 65 PSI cold, this tire carries 2,335 pounds. Multiplied by 4 (two axles), that's 9340 pounds. The GVWR for our trailer is 7,600 pounds. That gives us a 23% margin of safety over the maximum permissible load for the trailer. We're feeling OK about that. Yep, tows like a dream.
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Old 09-12-2016, 05:21 PM   #33
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Quote:
Originally Posted by Rocinante View Post

See page 11 and page 25.

At 65 PSI cold, this tire carries 2,335 pounds. Multiplied by 4 (two axles), that's 9340 pounds. The GVWR for our trailer is 7,600 pounds. That gives us a 23% margin of safety over the maximum permissible load for the trailer. We're feeling OK about that. Yep, tows like a dream.
Am I missing something here. I look at the chart and it looks like one would be good for 3880 LBS per axle (7760 total weight) at 50psi. So with my 28' having a ready to camp weight of 6500 - 6700 depending on the trip. I should be good to go with 50 psi. Is this not correct?
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Old 09-12-2016, 05:43 PM   #34
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LT225/75R16
4670 at 65 psi
4880 at 70 psi
What am I missing?
I have a tandem axle trailer with 8,800# on the trailer tires and 10,000# GVW.
Looks good to me.


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Old 09-12-2016, 08:40 PM   #35
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tire inflation psi

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Originally Posted by PSU1981 View Post
I know the max inflation for this tire is 80 psi & with this it has a max load of 2,680 lbs.

AS owners that have this tire -- what P are you running at & why?

We are in Texas where it can get quite hot in the summer --- do you recommend a different ambient temp inflation in summer vs. winter?

We have a 2015 27FB FC that I am upgrading the 15" GYM's to this tire.

Thanks,

Glenn
We have a 2012 Eddie Bauer 27 ft with Michlin 16" rims and we use between 75psi to 80 depending on the ambient temp Works great
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Old 09-12-2016, 08:54 PM   #36
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We have a 2012 Eddie Bauer 27 ft with Michlin 16" rims and we use between 75psi to 80 depending on the ambient temp Works great
Search on CapriRacer....it's all been covered.

IIRC, deduct 10% capacity for those of you running the 15" P tires and deduct another 15% for a margin for both P and 16" LT. That's 15% total for LTs and 25% for Ps.

(note: Not trusting my memory on the 15% figure...search and find)

Edit: Not sure why it quoted TSOMMY...meant to quote Arcticfox...weird glitch
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Old 09-12-2016, 09:07 PM   #37
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Hi there. That page shows numbers for two tires, one on each end of the axle, whereas the other page shows per tire. So while one tire will carry 2335 at 65PSI, two tires would carry 4670 at 65PSI. Confused me at first as well, hope that helps.

Quote:
Originally Posted by Arcticfox View Post
Am I missing something here. I look at the chart and it looks like one would be good for 3880 LBS per axle (7760 total weight) at 50psi. So with my 28' having a ready to camp weight of 6500 - 6700 depending on the trip. I should be good to go with 50 psi. Is this not correct?
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Old 09-12-2016, 09:28 PM   #38
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Quote:
Originally Posted by Rocinante View Post
Hi there. That page shows numbers for two tires, one on each end of the axle, whereas the other page shows per tire. So while one tire will carry 2335 at 65PSI, two tires would carry 4670 at 65PSI. Confused me at first as well, hope that helps.
Ok it official I'm more confused now than ever....

According to the chart (for two tires) the PSI at 50lbs would be 3880 (or 1940 per tire). Now I have 4-tires so I would still then take the (1940x4) or (3880x2) and still get 7760 lbs as an acceptable weight to have on these tires.

Now if you look at it at your desired setting of 65lbs the cart indicates that you should be carrying 9340lbs (4670x2) or (2335x4). So in my mind the cart is telling us that 65 lbs is to high and 50 is closer to what our trailers come in at.

Now as I posted earlier in this thread. I contacted Andrew Thompson from Can-Am who is considered an expert on towing and hitches. He responded to my email stating that with a ready to camp weight of 6500 - 6700 LBS he felt my tire pressure should be 45 - 50 lbs cold. From what I can gleam from this chart, I would say he is very close and the tire manufacturer is backing his finding up with this chart.

Again, am I missing something here?
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Old 09-12-2016, 09:33 PM   #39
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Ok it official I'm more confused now than ever....

According to the chart (for two tires) the PSI at 50lbs would be 3880 (or 1940 per tire). Now I have 4-tires so I would still then take the (1940x4) or (3880x2) and still get 7760 lbs as an acceptable weight to have on these tires.

Now if you look at it at your desired setting of 65lbs the cart indicates that you should be carrying 9340lbs (4670x2) or (2335x4). So in my mind the cart is telling us that 65 lbs is to high and 50 is closer to what our trailers come in at.

Now as I posted earlier in this thread. I contacted Andrew Thompson from Can-Am who is considered an expert on towing and hitches. He responded to my email stating that with a ready to camp weight of 6500 - 6700 LBS he felt my tire pressure should be 45 - 50 lbs cold. From what I can gleam from this chart, I would say he is very close and the tire manufacturer is backing his finding up with this chart.

Again, am I missing something here?
The chart reflects a passenger tire or LT installed on a TV, not a trailer. Again, Search on the tire engineers' posts for "penalties", or margins necessary when placing a TV tire on a TT.
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Old 09-12-2016, 11:09 PM   #40
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Per the tire engineers around here, there's no "penalty" or "de-rating" for LT (light truck) tires on trailers, though said de-rating does apply to "P-metric" (passenger car) tires. There are lots and lots of threads on this topic that clarify the issue, just use the "Google" search feature to find threads that discuss de-rating in detail.

Agree that at 65 PSI per the load table above our tires could carry 23% more than is absolutely required. Again, per the tire engineers here, even without de-rating it's not a bad idea to have a safety margin - in part because some tires may carry significantly more weight than others based on how the trailer is loaded. So, we went with 65 PSI in our tires.
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Old 09-13-2016, 07:15 AM   #41
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And don't forget side to side and front to rear weight variation. The tires on a trailer do not carry the same amount of load.
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