Safe Tire Pressure

[CapriRacer]

Originally Posted by richinny

dznf0g

since you've got such an interest in tire pressure i was wondering if you've tried filling the tires with nitrogen? your customary detailed reporting would give it a lot of credibility.

I saw dzn's response - and I hope folks have seen my thoughts:

Barry's Tire Tech

Just like the guy selling TPMS's, I think nitrogen inflation has been subjected to a bunch of snake oil tactics and claims. There isn't any harm, but there isn't any real advantage either. If you get it free - Great! But it isn't worth paying for.

[dznf0g]

Originally Posted by CapriRacer

I saw dzn's response - and I hope folks have seen my thoughts:

Barry's Tire Tech

Just like the guy selling TPMS's, I think nitrogen inflation has been subjected to a bunch of snake oil tactics and claims. There isn't any harm, but there isn't any real advantage either. If you get it free - Great! But it isn't worth paying for.

UNLESS....you're driving for a race team and 1/4 psi difference in pressure is the difference between the winner and the first loser. But for a street car, not enough of a benefit, IMO, to even waste the gas to get them topped off, even if it were free.

One other application I would use it for. Antique or collector cars, where they sit in storage or museum for LOOOOONG periods of time. Nitrogen MAY, MAY prolong their display life.

[dznf0g]

Originally Posted by CapriRacer

There is no "target". There is only a trigger level where action should be taken.

- and no, it isn't different between the 2 types of tires (or any tire, for that matter).



I don't think it is. If folks are getting this type of thing, the engineer in me would want to investigate further to make sure this is what it is claimed to be.

On a variety of comapny cars and truck, unladen, 65 mph, I most all the time see only a 4psi rise from cold ambient on the TPMS readout. Very consistent. Disregarding sun loads and wind direction.

[purman]

Originally Posted by w7ts

I think we are talking about opposite ends of the body.

Oh, I didn't realize you we're talking about your butt.

[A W Warn]

October 18, 2012


Hello,


Thank you for your email. We welcome the opportunity to serve you.

In regards to the email you sent stating:
---------------------------------------------------------------------
Thank you for your prompt response.
I would appreciate further clarification to one of my original questions. Does Michelin warranty LT tires used for RV trailers?
The reason I am asking this question, I noticed Airstream uses Michelin light truck tires on at least one 2012 model of their trailers. I also looked on Airstream's website and saw that some of their models offered Michelin tires as an option as far back as the 1970's. I find that Airstream offers Michelin tires, as replacements for the original ST tires, at their factory service center.
I assume these tires are adequate to support the loads of these trailers or Airstream would not offer them. What is Michelin's official stance on warranty of a LT (light truck) tire when mounted on a RV trailer? I am considering doing this on my Airstream though I would be purchasing from a local dealer, not the Airstream service center.
Thank you in advance for your response!
---------------------------------------------------------------------



If the RV came original equipment with a ST tire, we do not recommend replacing with a light truck tire as this would be considered a misapplication. There is no warranty for misapplication.

Please let us know if you have additional questions.

Thank you for contacting Michelin.

It is our goal to ensure that your issue has been resolved or your question answered to your satisfaction. If we can assist you further, please respond to this email or call us at 1-800-642-4354 (toll free) between 8:00AM and 8:00PM Eastern Time Monday through Friday or between 8:30AM and 4:30PM Eastern Time on Saturday.

Sincerely,

Consumer Care Department
Certified Michelin Product Expert

[Ag&Au]

Alan,

As silly as that reply sounds to me, it doesn't surprise me at all. Now I wonder what Airstream would say about that. According to Michelin's statement, they would stand behind the tires mounted on the Eddie Bauer model, but not the ones the factory provides to replace ST tires. This is particularly strange, because as I understand it the factory will place LT tires on new trailers as an option. Now will those be OK with Michelin?

Ken

[Moflash]

What is Michelin supposed to say? I am sure that they have not tested Lt tires on Airstream travel trailers.It does not mean they wont perform well.
I think if you spend some time reading the forum it is fairly easy to figure out how well the Lt tires perform on our trailers.We have tested them on our trailers.
Then compare how well the ST tires have performed we have tested them also.Draw your own conclusions.

You might as well have asked them if they would warranty the tires if used for a tire swing.
The answer would have been the same........My 2 cents

[A W Warn]

Re: all of the above questions and comments (and any after this), I have no answers, nor strong opinion either way. I was just sharing the information.

[slowmover]

Part of the "answer" to these questions, for me, was:

Craftsman Horizontal 3-gl Air Compressor

as ten tires to keep up with warranted something decent. A little heavy, and a little big (except when ones "traveling garage" is the back of the pickup truck). This dude is fast. (And will have other uses on a project trailer). About a foot and half high.

Now just need an equal quality air gauge.

Good questions above.

I'm sticking with "simple" (max on TT, and staying inside TV mnfrs numbers with a bit of experimentation up or down), and, as I don't intend to travel at high speeds (65+) solo or towing, hope that no more than morning temps & altitude will affect readings. As daily tire pressure readings -- prior to any travel -- is a basic (along with re-torquing wheel stud nuts), the 10% pressure rise maximum seems seems simple.

Individual weight scale readings on all wheel positions to work from (TV done, TT yet to come once on scale with WDH applied) as the beginning.

Gonna have to go read that TPMS thread now.

.

[slowmover]

Originally Posted by dznf0g

Well, I found something. Have no idea as to the credibility of this read. Capriracer....care to share your knowledge as to these temps and how we may interpret them using infrared on the outside of the tire shoulder and using TPMS (both the pressure rise method and stem air temp method)?

Why Temperature?

(is there an error in #2 sub section 3? Shouldn't those be Farenheit figures, not Celsius?)

80C = 176F

I guess I'm dull after some long days behind the wheel. What is it you're trying to find (or be able to predict)?

.

[dznf0g]

Originally Posted by REDNAX

80C = 176F

I guess I'm dull after some long days behind the wheel. What is it you're trying to find (or be able to predict)?

.

I am trying to understand why I have 7 -9 psi rise on the AS Michelins at 65 and 70psi cold with a little less than 2000 lbs load on each tire. It makes no sense to me compared to P and LT tires on the TVs and cars I have driven and does not correlate to what I would expect per the load/pressure charts. 7 - 9 psi is too much of a rise and indicates a 70 - 90* rise in temp.......but how to verify that?

What does 70 - 90* rise in internal air temp mean relative to the actual rise in temp in the shoulder area....and how do we measure that without a partially destructive probe Pyrometer? That is ALL the discussion above in a nutshell and abbreviated.

[slowmover]

Thanks. I gits it now. Prediction

To cover the bases (and for those wishing to replicate method):

1] Are these pressures taken after at least 1.5-hrs steady state driving? Versus cold pressures taken that morning prior to departure? Easy braking to the full stop? (Preferably readings from a number of stops).

2] The load on the individual tires is taken from scale data with WDH applied?

3] The axle alignment is verified dead-on perfect? No brake drag? Bearing pre-load is correct? Axle rubber pliable/functional? The hitch is not canting the trailer to one side or another (entirely possible depending on type/brand)?

I've written that I am in favor of max sidewall pressure on TT's from what I have learned the past few years. On the TV I would prefer to have the "lowest" correct pressure, so the point where the pressure rise is no more than 10% sort of sets itself (respective of vehicle manufacturer range of pressures, FF & RR; load reserve, etc).

If we had your TV under tow, some of the same "problems" might arise that come up with a trailer. Especially if we were yanking it around with a ten foot bar and it didn't perfectly track the vehicle towing it. And it won't.

The trailer is always moving around. Side-to-side. Have someone follow you with a video camera. Unless that trailer is hitched with a PULLRITE or a VPP style, it will be moving around more than necessary. Minimizing this motion changes stress on the tires. Winds cause the trailer to tilt as well, so the motions are from different directions (say, traffic and local winds). An aero trailer has winds pulling at it with no other type effects (versus a box type where winds push; this is relative), and all this must be set against the "pole" yanking it down the road.

Then add in road problems (grade, surface, etc).

Cumulative effects.

Think this leads in the right direction?

.

[dznf0g]

Red, Affirmative to all questions. I think you've read enough of my stuff to know how anal I am. See my reply to your post on the TPMS thread. Not sure I have a problem. Not sure which temp vs. pressure calculations to believe.

[slowmover]

Read that and replied. I don't think it a matter of what correction seems best outside of repeatable results. If I have an upper limit monitored (temps) and the pressure rise during the day is predictable, haven't I then covered this pair of bases (for that day and on that drive)?

I don't see a problem when we posit that TT tires undergo different stresses than the TV it is following.

Reading both Barry's Tire Tech and Rogers RV Safety blog covers quite a bit on one hand, but one also comes away with what isn't said due to constraints of time, energy and engineering contexts. The threads on this forum -- and on the other RV forums (and others besides) to which they have contributed -- have added a great deal to what we may consider "safe travel", IMO.

Still, the search for "best" goes on, ha!

.

[dznf0g]

OK, so the last weekend of the season has ended..

Relative to the above posts:

I ran the LTXs at 80 psi, and saw only a 5 - 7 psi rise....well within the 10% of starting pressure. I am thinking this is the only accurate way to definitively decide on pressures in a non-conventional tire application.

I noted no evidence (at least on this short 150 mile hop) of a decreased ride quality. Towels still on the rack, etc.

I may try 75psi next spring and see if that is the 10% sweet spot.

[purman]

Ok I just got back from Zion NP last weekend. 450 miles one way, 900 total. I ran my Michelins at 65 psi and had up to 6psi rise over all. Tires never ran warming than the TV by touch. Around 90 degrees. No problems and a smithy ride. My trailer weighs about 7000 lbs loaded. I'll be running 65 psi, don't see a need to run any higher.

[dznf0g]

I weigh in at about 9000# loaded. There's the diff. By the temp rise method (if it has merit) 6psi at 65 psi should be good. I was getting up t0 9psi rise at 65 PSI.

[Ag&Au]

Originally Posted by purman

Ok I just got back from Zion NP last weekend. 450 miles one way, 900 total. I ran my Michelins at 65 psi and had up to 6psi rise over all. Tires never ran warming than the TV by touch. Around 90 degrees. No problems and a smithy ride. My trailer weighs about 7000 lbs loaded. I'll be running 65 psi, don't see a need to run any higher.

I'm not sure what this means. I am guessing it means a ride like a blacksmith's hammer hitting an avil.

Ken

[dznf0g]

Originally Posted by w7ts

I'm not sure what this means. I am guessing it means a ride like a blacksmith's hammer hitting an avil.

Ken

Ah, but SMITHYS use to build soft springies for the ladies' buggies as well. They had a more feminine side to their hammer and anvil!!!!

[dznf0g]

Originally Posted by REDNAX

I am thinking this is the only accurate way to definitively decide on pressures in a non-conventional tire application.

But for the TT, again, it is about the stresses on the tire which are not those experienced by the TV, and they aren't going to show in psi rise. It's the turns (nearly all of them), all of the backing to & fro, etc. U-turns on fresh concrete the worst. Pressure versus load doesn't matter for TT tires. The damage is internal and cumulative.

Purman, it's the norm for the TV tires to run hotter than the TT tires (if you're using an IR gun to check tread temps at a gently made stop coming off the highway).

I am not convinced I buy this. I have pondered and waffled on it a lot. A heavily loaded truck, with LT tires traveling at 65 MPH, and a pretty harsh turn on a 2 laner....I just am not so sure the stresses are that much greater than a low speed scrub on a trailer. At speed, the scrub on a trailer isn't that great, IMO.

I think it is over estimated by most.