16" wheels/LT tires

[dkottum]

The discussion is confusing to say the least and has not become more clear since the tire engineers came in.

I've given up trying to understand it and am following experience. Original GYM's fail regularly so I sold them. Michelin 16" LTX MS is used by Airstream as a premium upgrade, and many, many Airstreamers with virtually no failures.

So I put them on the Airstream and quit worrying about it.

Then the question of tire pressure came up. Airstream uses and recommends 80 psi for whatever reason, doesn't matter. That's not clear either, and the tire engineers have not made it any more clear. Experienced Airstream repair shop owners tell us 80 psi gives too hard a ride for our trailer, and suggest less based on their experience. Andrew Thomson at Can-Am recommends tire load charts to determine adequate pressure for a particular trailer.

After considering his extensive Airstream experience, generic tire engineer advice, and some general forum advice anything less than 80 psi will result in dangerous sway, and advice from others using the 16" Michelins, I have settled on 65 psi for our 25' Airstream.

We just took a 2500 mile trip with no hint of sway or wind push (ProPride hitch installed), no excessive rollover of sidewall when backing at an angle, and no unusual heating of the tires during travel.

That's one Airstreamer's User Report.

[willapus]

Originally Posted by Silvery Moon

Ok, so how about these General Grabber HTS tires for 15" wheels? They seem to have a higher rating than the Michelin 15" tires, which according to the Michelin site are rated for only 1985 pounds. The 109T rated General Grabber HTS in 235/75R15 XL is rated at 2271 pounds with max inflation pressure of 51 pounds. If that's a good tire, it would seem a better choice than the lower-rated Michelin...unless I am misunderstanding, which is entirely possible.

Oh, and the General is a "low rolling resistance" tire, which sounds like it might be helpful for better MPG when towing.

http://www.michelinman.com/tire-sele...ails#techspecs
http://www.generaltire.com/tires/lig...bber-hts#Specs

Thoughts?

I have used the grabber hts on my previous 2002 sequoia. I switched from Michelin road tires, I can't quite recall the model name maybe cross terrain, to the general grabber hts p rated and loved them. After serval years I bought my streamline and then switch those p rated tires to an LT E rated tire in an effort to help reduce sway. They helped but the sequoia rode like a truck when it was unloaded, which was about 80% of the time. So yes I like the grabber hts, but would get it in an LT model for the trailer. I have switched sequoias and the sway is greatly minimized. I have the Kumho "venture apt" LT 225/75 r 16 on my streamline and have put 10,000 miles on them between the two tv's. They seem to be holding up just fine.



__________________
Will
'67 29' Streamline Empress
'05 Toyota Sequoia 4x4
'65 Buick Electra 225 convt.

[Ag&Au]

Originally Posted by dkottum

The discussion is confusing to say the least and has not become more clear since the tire engineers came in.

I've given up trying to understand it and am following experience. Original GYM's fail regularly so I sold them. Michelin 16" LTX MS is used by Airstream as a premium upgrade, and many, many Airstreamers with virtually no failures.

So I put them on the Airstream and quit worrying about it.

Then the question of tire pressure came up. Airstream uses and recommends 80 psi for whatever reason, doesn't matter. That's not clear either, and the tire engineers have not made it any more clear. Experienced Airstream repair shop owners tell us 80 psi gives too hard a ride for our trailer, and suggest less based on their experience. Andrew Thomson at Can-Am recommends tire load charts to determine adequate pressure for a particular trailer.

After considering his extensive Airstream experience, generic tire engineer advice, and some general forum advice anything less than 80 psi will result in dangerous sway, and advice from others using the 16" Michelins, I have settled on 65 psi for our 25' Airstream.

We just took a 2500 mile trip with no hint of sway or wind push (ProPride hitch installed), no excessive rollover of sidewall when backing at an angle, and no unusual heating of the tires during travel.

That's one Airstreamer's User Report.

Airstream and any other tire and vehicle dealer* that I have dealt with will always inflate tire to the pressure required for Max Rated Load on the sidewall for one reason. That reason is to avoid liability. They do not want to make all their customers fill out a form stating what load they are going to be carrying and then calculate the appropriate pressure. If they always use the maximum load pressure, they are always safe, and it makes their job a lot easier.

You have to chose whose advice to follow. My personal opinion is that there are so many variables involved that is it not necessarily true that the blanket statement about " too hard a ride" is taking all variables into account any more than "always use maximum pressure is".

Ken

* some vehicle dealers will use the placard on the vehicle, but will always use the Max load value on that placard

P.S. I feel that 65 PSI is appropriate for your 25 foot trailer and 80 is appropriate for my 31 foot trailer.

[slowmover]

Originally Posted by Ag&Au

I would have to think about this concept for a while before I accepted it. Tires are rated for moving at their max rated speed and the associated flexing, scuffing and heating involved. When sitting still in a campground or wherever, none of those dynamics are occurring, and a certain amount of the weight is being born by the tongue jack. So my instincts tell me what happens when parked is not a factor. (within reason of course).



If I am misinterpreting what you said, then "never mind" .



Ken

I'd say that if rated load is nearing margin then this ought also be considered. Especially on uneven ground and uneven loads on tires.

[Action]

Long term storage ....

Non-moving tires do not see near the stress like the heat, road hazards, side wall flexing in turns and dynamic forces of meeting uneven road surfaces. In addition some stress may be removed when stabilizers and tongue jack are down. Nearly any tire will serve for that purpose and long term storage will accelerate tire decay (rot) as the tire is not being used and flexed. Tread depth becomes a non-issue.

>>>>>>>>>Action

[Vlamgat]

So everyone keeps throwing the term "rating" around and I would suggest that no one (certainly on this forum) has the any idea what that really means other than the load tables published by manufacturers. I also think there is enough evidence around to show that these are more guideline than gospel. and as guidelines they suck for many of the reasons that have been posted. Manufacturing quality for one but also ambient and road surface temperatures, pressures, moisture levels inside the tire, alignment and both fore/aft as well as left/right loads amongst several. And then there are those that have chimed in agreeing that the load rating is essentially the maximum weight to be a carried at any time and therefore one should allow for this and build in a reserve of 10 to 15%. That presumes to know that the manufacturers were guessing at the load rating; or worse that the rating was defined under specific conditions for the probable/likely warranty time/distance only. But even perfect conditions is a hard definition to pin down: roller drum at ISA; constant speed; clean and dry inflation and no need or cause for sidewall flex as might be produced by a cross wind. Who knows?

Lets face it its trial and error and thanks to the experiences on this site I have been able to benefit from some of the more successful trials.

Just in case it makes any difference: I have weighed my trailer in all 4 dimensions in a typical load condition; multiplied the heaviest wheel load by 4; and upped that amount by 10%. Then looked for a tire that would carry that load and fitted the 16" Michelin XPS Rib LRE. But its maximum load is 15% more than I need at 80 psi so I inflate to a 76 psi or 5% less than maximum based on a a 70 deg cold ambient. I decrease that inflation by 1 psi per 10 degrees ambient but no lower than 69 psi. Meaning that on a winter morning when the temperature is (say) 20 degrees my starting pressure is 71. As it would also be if the starting temperature was zero. Similarly when the starting temp is 90, I check for a 78 deg start pressure.

Science? Some - We do this with aircraft and car rally tires where the same issues apply although the former does not have as frequent a side load issue. But this is not gospel, based on "tested" science. Just bitter experience and a healthy disrespect for the tire industry.

[Ag&Au]

Originally Posted by Vlamgat

So everyone keeps throwing the term "rating" around and I would suggest that no one (certainly on this forum) has the any idea what that really means other than the load tables published by manufacturers.


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Science? Some - We do this with aircraft and car rally tires where the same issues apply although the former does not have as frequent a side load issue. But this is not gospel, based on "tested" science. Just bitter experience and a healthy disrespect for the tire industry.

I pretty much agree with everything you wrote. However, because I am a skim reader, you may have slipped one or two things by me.

My best advice to myself (which I heed) is to always be on the safe side of experimentation, so I can learn from the mistakes of others rather than my own. I don't give this advice to others, because I always want someone on the cutting edge ahead of me.

Ken

[BoldAdventure]

Originally Posted by Vlamgat

So everyone keeps throwing the term "rating" around and I would suggest that no one (certainly on this forum) has the any idea what that really means other than the load tables published by manufacturers. I also think there is enough evidence around to show that these are more guideline than gospel.

Clearly the manufacture doesn't know WTF they are talking about when they stamp a load rating on a tire.

[JimAspinwall]

I can't believe this has gotten so convoluted.

Either go by the absolute published numbers, or factor in your own comfort/safety/fudge factor, be it 10%, 15% or 80%. But guessing what engineers, lawyers, the DOT, NTSB, and 50 states have factored-in is, well, guessing - not data.

I had 3 blow outs of generic 3+ year old TRAILER tires in one weekend. That SUCKED. After reading similar not-complimentary experiences of others with "trailer tires" I needed "an answer."

Airstream has 'adopted' the 16" Michelin MS/2 LTX as stock/standard/blessed/approved/certified A-OK for 2015+ trailers, and upgrades to prior models. THAT was the final decision point for me.

I ordered a set of Sendel T03 wheels, called my tire guy, had him provide a new 16" steel rim for spare and 5 Michelins. Done.

Michelins have lasted longer in tread wear and stability on half a dozen vehicles from a 1999 Volvo S-70 that easily handles 110 MPH+ to a 1973 Datsun 240z to an 88 Isuzu Trooper and on and on. If I can get suitable Michelins for my 2500 HD Silverado when I need them, I will.

If 4x the tire's single published load rating is not equal or greater than your trailer gross weight then you can expect to have a problem using them.

If you overload your trailer (it can be done) beyond tagged gross weight - shame on you. A scale weigh-in, if you can find one, costs less than a week's worth of St*rbucks.

The only thing I will say about changing from supposedly stiff-sidewall 'trailer' tires to light truck tires is that yes, you may notice a little more 'motion' from the trailer than before, even with a Hensley hitch, but I just did a 1200 mile mountain/switchback trip into and out of 104 deg conditions and adjusted to the difference as OK.

As a mentor tells me often: "the price of quality only hurts once"

Do you trust Airstream, Michelin and Sendel, or not? So far I have heard NOTHING bad about either of those three.

[CapriRacer]

Originally Posted by BoldAdventure

Ok, great to know then.

So the Michelin LTX M/S2 in 225/75R16 rated at 2680 lbs. with 80 psi.

Derated 10% for Trailering = 2420 lbs. and with a safe margin of 15% = 2057 lbs.

2057 lbs. x 4 tires = 8228 lbs rating. ......

Sorry, but there is an error there. The tire in the box above is an LT tire (Which is one of the reasons I always use the letters in front of or behind the tire size.) - and the 10% doesn't apply to LT tires - only P type tires.

Originally Posted by BoldAdventure

........Which means trailers with 10,000 GVWR running these would be way over a safety margin based on above advice. ?? .....

So redoing the math, that's 9,112#.

and if we assume the GVWR includes the hitch weight, and the hitch is 15%, then the trailer's tires are actually experiencing 8,500#.

So that works.

Originally Posted by BoldAdventure

........But this completely kills it on the 15's.

Michelin LTX M/S2 in 235/75R15 at 50 psi. rated at 2183 lbs.

Derated 10% for trailering = 1964 lbs.
Derated 15% safety = 1669 lbs

1669 x 4 tires = 6676lbs rating.

I think you can see the problem.

[Ag&Au]

Originally Posted by CapriRacer

Sorry, but there is an error there. The tire in the box above is an LT tire (Which is one of the reasons I always use the letters in front of or behind the tire size.) - and the 10% doesn't apply to LT tires - only P type tires.



So redoing the math, that's 9,112#.

and if we assume the GVWR includes the hitch weight, and the hitch is 15%, then the trailer's tires are actually experiencing 8,500#.

So that works.



I think you can see the problem.

OK, so basically as I understand it, there is no industry recommendation for lowering the max load for LT tires used in trailer service. To me that is the problem. You are saying that we should use 15% for all tires in all uses, as I understand you. However when we get down to it, who are you?

The internet is a interesting place where people routinely convincingly represent themselves as someone or something they are not. You in this case are presenting yourself as a tire expert here and on your website, yet unless someone here knows you in a real world context and has not mentioned it or I missed it, we have nothing to verify what you tell us as fact as opposed to just someone's opinion. I will admit you are very convincing, but apparently to some so are Nigerian princes wanting to spirit ill-gotten wealth out of Africa through someone else's bank account.

Therefor until something changes, and I find out there is more known background to who you are, I am going to read what you say, but consider it in the same light as other information on the internet from an unverified source.

This was not intended to insult you, but just to point out that if one obscures one's background to the point it cannot be verified, the information they present must be taken with that in mind.

Ken

[TinTin]

switz posted an excellent link some time ago regarding regulations related to use of passenger tires on travel trailers.

A quote:

49 CFR 571.110

Tire selection and rims and motor home/recreation vehicle trailer load carrying capacity information for motor vehicles with a GVWR of 4,536 kilograms (10,000 pounds) or less.


S4.2.2.1
Except as provided in S4.2.2.2, the sum of the maximum load ratings of the tires fitted to an axle shall not be less than the GAWR of the axle system as specified on the vehicle's certification label required by 49 CFR part 567. If the certification label shows more than one GAWR for the axle system, the sum shall be not less than the GAWR corresponding to the size designation of the tires fitted to the axle.

S4.2.2.2
When passenger car tires are installed on an MPV, truck, bus, or trailer, each tire's load rating is reduced by dividing it by 1.10 before determining, under S4.2.2.1, the sum of the maximum load ratings of the tires fitted to an axle.

S4.2.2.3
(a) For vehicles, except trailers with no designated seating positions, equipped with passenger car tires, the vehicle normal load on the tire shall be no greater than 94 percent of the derated load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.
(b) For vehicles, except trailers with no designated seating positions, equipped with LT tires, the vehicle normal load on the tire shall be no greater than 94 percent of the load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.

The link:

http://www.gpo.gov/fdsys/pkg/CFR-201...sec571-110.pdf

[Inland RV Center, In]

Thought I would throw this in.

15 inch tires have a circumference of 94.25 inches.

16 tires have a circumference of 100.5 inches.

That means in a mile the 15 inch tire turned 672 times and the 16 inch tire turned 630 times.

So, at a give speed, a 16 inch tire turns about 6 percent slower, than a 15 inch tire.

But, in both cases they still need balancing with the hub and drums.

The only advantage that's clear to me is that the 16 inch tire raises the trailer about one inch.

But, if 16 inch tires are added to a new axle/axles, then the trailer will raise about 4 inches.

Now your talking. :smile:

Andy

[Ag&Au]

Originally Posted by TinTin

switz posted an excellent link some time ago regarding regulations related to use of passenger tires on travel trailers.

A quote:

49 CFR 571.110

Tire selection and rims and motor home/recreation vehicle trailer load carrying capacity information for motor vehicles with a GVWR of 4,536 kilograms (10,000 pounds) or less.


S4.2.2.1
Except as provided in S4.2.2.2, the sum of the maximum load ratings of the tires fitted to an axle shall not be less than the GAWR of the axle system as specified on the vehicle's certification label required by 49 CFR part 567. If the certification label shows more than one GAWR for the axle system, the sum shall be not less than the GAWR corresponding to the size designation of the tires fitted to the axle.

S4.2.2.2
When passenger car tires are installed on an MPV, truck, bus, or trailer, each tire's load rating is reduced by dividing it by 1.10 before determining, under S4.2.2.1, the sum of the maximum load ratings of the tires fitted to an axle.

S4.2.2.3
(a) For vehicles, except trailers with no designated seating positions, equipped with passenger car tires, the vehicle normal load on the tire shall be no greater than 94 percent of the derated load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.
(b) For vehicles, except trailers with no designated seating positions, equipped with LT tires, the vehicle normal load on the tire shall be no greater than 94 percent of the load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.

The link:

http://www.gpo.gov/fdsys/pkg/CFR-201...sec571-110.pdf

After the above post, another member posted that this seemed straightforward to him. He apparently then deleted that post. However after all the chaff has fallen to the ground I agree with him.
From reading the above, it is obvious that "Passenger tire" refers to "P" rated tires, not any tire for a vehicle that carries people. It is apparent to me that no lowering of weight rating is required for "LT" tires on a trailer.

What this all boils down to is whether or not you wish to follow one man's advice to lower all weight ratings on all tires by 15%. Since the case used support the 15% is applicable to any max rating of any product, I am choosing to ignore it at as a specific recommendation for this subject. I have chosen to use tires whose combined weight ratings exceeds the GVWR of the trailer. Now it is my job, as it has always been, to be sure the GVWR of the trailer is not exceeded.

Ken

[slowmover]

The short of it is to keep max load at 85% for LT tires in trailer service and to keep pressure at sidewall maximum.

This is the reasonable starting point.

[Ag&Au]

Originally Posted by slowmover

The short of it is to keep max load at 85% for LT tires in trailer service and to keep pressure at sidewall maximum.

This is the reasonable starting point.

Why do you say at 85% rather than under 100%?

Ken

[slowmover]

Thanks. I should have put differently. Tire load index should be 115% of requirement. TT GVWR should be baseline.

[TinTin]

Wading into tire threads is never wise. However, regarding de-rating of tires for trailer use, this is what would appear to make sense to me (hopefully I'm not just repeating what others have said:

LTX tires (P metric): de-rate by 10% due to mis-application
LT tires: de-rate by 10% due to mis-application
ST tires: no need to de-rate (no mis-application)

In addition to the above, it would be great to leave an adequate safety margin of an additional 10-15% for perfect peace of mind.

[Ag&Au]

Originally Posted by slowmover

Thanks. I should have put differently. Tire load index should be 115% of requirement. TT GVWR should be baseline.

I agree with to that if it is to compensate for the fact that there is no way for the load on all four tires to be equal. However I do not agree if the 15% is required just because its a trailer.

I am curious if, on a truck with tandem rear axles, are the rear tire's weight ratings adjusted for scuffing in turns? I am curious because there is bound to be be more scuffing there than on a trailer, because there is no point of rotation (trailer hitch) to lessen the scuffing.

Ken

[TinTin]

Originally Posted by Ag&Au

I am curious if, on a truck with tandem rear axles, are the rear tire's weight ratings adjusted for scuffing in turns? I am curious because there is bound to be be more scuffing there than on a trailer, because there is no point of rotation (trailer hitch) to lessen the scuffing.

Ken

18 wheelers are truck and trailer (with hitch). Sideways scuffing would probably be similar to our Airstreams, scaled up by a big weight difference factor. Pretty sure they use tires designed for the application.