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Old 02-28-2013, 12:22 AM   #1
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Tire related questions

Itís my understanding that ST tires, differ from P and LT in the following ways.

#1 ST tires are designed for seldom use with special UV inhibitors and possibly different ply materials and/or ply orientation to servive or prevent flat spotting.
#2 ST tires have shallow tread and to reduce wondering.
#3 ST tires have sidewalls designs to not peel off the rim in a tight turn. Not sure that would even apply to single axle trailers.
#4 ST tires have sidewall stiffness that is firmer than same rated P, and less firm than same rated LT.

Iíd like to know if:
A: Do these statements accurately portray what tire industry says about ST tires?
B: Have any of you that use LT on your trailer, experienced any of the four problems that the ST is designed to prevent? Example; Have you peeled an LT off of your wheel while backing into a campsite? LT problems due to UV?
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Old 02-28-2013, 07:27 AM   #2
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First, I think there is a lot of variation within the tire industry regarding ST tires. I'll try to answer your questions with my best guesses. Just be aware that any particular statement MIGHT not be universally true.

Quote:
Originally Posted by Not Done View Post
Itís my understanding that ST tires, differ from P and LT in the following ways.

#1 ST tires are designed for seldom use with special UV inhibitors and possibly different ply materials and/or ply orientation to servive or prevent flat spotting.

......................
UV inhibitors? Maybe, maybe not. I'm not convinced that anyone is doing anything extra.

You didn't mention Antioxidants? These are expensive and I don't think these price sensitive tires would get more than the norm.

Flat spotting? Absolutely not true. Vibrations in trailer tires are not an issue. We have people saying they don't even balance trailer tires.

Quote:
Originally Posted by Not Done View Post
......

#2 ST tires have shallow tread and to reduce wondering.

.............
Shallower tread? Yes - but to reduce cost not to reduce wandering.

Quote:
Originally Posted by Not Done View Post
........

#3 ST tires have sidewalls designs to not peel off the rim in a tight turn. Not sure that would even apply to single axle trailers.

.............
Nope. As a tire engineer, the things that COULD be done would also apply to both P metric and LT metric tires and it would make sense to do all 3 if you were going to do that.

Quote:
Originally Posted by Not Done View Post
.........
Quote:
Originally Posted by Not Done View Post

#4 ST tires have sidewall stiffness that is firmer than same rated P, and less firm than same rated LT.

.............
The key here is "same rated". For practical purposes there isn't any overlap - unless you start messing with size, and that's a whole different kettle of fish.

I think it is safe to say that ST tires are built stiffer than same sized P metric tires - but ST tires also carry more load (for the same size) - and they are inflated to higher pressures, so they need that extra reinforcement.

I am of the opinion that LT tires and ST tires are - for practical purposes - the same, with the differences being changes for the intended service (eg shallower tread depths) or cost considerations (eg shallower tread depths, narrower tread width) - and the difference in load carrying capacity is a reflection of the intended service (trailers vs motorized vehicles)

The above is based on my experience as a tire engineer and not as a trailer owner.
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Old 02-28-2013, 09:48 AM   #3
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I have been using LT tires (225/75X16"R Goodyear LR E) on our trailer for about a year now with no ill effects, and I might add at least a small amount of increased peace of mind.

However, for one year, I know ST tires would probably have performed well, but I've seen lots of failures from seperation and lots of damage done to Airstreams as result.

If you study the tire weight carrying capacity charts, you will find there are no comparable size P, or even LT tires that will carry the weight of ST tires, but you will also find no P or LT tires with the 65 MPH speed restrictions of the ST tires.

Now, I do not know this for a fact, but I suspect the tire manufacturers artificially boost the weight specs on the ST tires and for the most part, get by with it, by restricting the speed to 65MPH.

I will also add my opinion, and that is I have bought my last ST tire.
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Old 02-28-2013, 11:50 AM   #4
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I have been running p metric (Michelin LTX) tires fo the last 4 years on a 25' trailer. I have had no problems. been to Alaska and across the country several times. to me the trailer seems to track fine. I do a right angle back to a paved driveway to park. The tires have no problem with this. I think it is less stress than turning the steering lock to lock puts on the front truck tires.
I will buy new tires for it this spring. will replace with the same tire.
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Old 02-28-2013, 11:55 AM   #5
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There will be issues with speed, throwing tread off
Motorcycle tires are rated for speed (Z, 120 mph), as are tires for cars like corvettes.
I'm convinced my tire failures (three of seven) on my Alfa were caused from getting a run at grades (up to 70 mph) and throwing tread. A switch from the stock uniroyals 225/16 LT to Bridgestone's of same size fixed my issues. I couldn't go larger without different offset wheels to fit 235/16 which would give me higher weight ratings.
Ever wonder what those cowboys are running towing those horsetrailers @ 90 +
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Old 02-28-2013, 01:36 PM   #6
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The cowboys around here run 10 ply truck tires. And they still will rip a fender off and tear up the side of their trailer.
Between running them way too long and not checking air pressure or condition, along with driving too fast.
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Old 02-28-2013, 03:57 PM   #7
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Quote:
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......... Between running them way too long and not checking air pressure or condition, along with driving too fast.
I suspect (excluding road hazards) the above encompasses 95 to 98 % of tire failures. Not based on actual data just my pondering.

Other possibilities of tire failure are;
defects
mis-matched tires to load
mis-matched set of tires
Unknown failure after a total loss
Out of balance tire/wheel assembly
Mis-aligned tire/wheel assembly

And the dramatic failures will always get the attention while in many cases of drama, the cause of the drama is mostly the smallest percent of all possible causes.

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Old 03-06-2013, 08:45 AM   #8
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The following quote is from the most current Carlisle tire information sheet.
 
ďThe slightly shallower tread depth of a trailer tire reduces sway and rides cooler, which adds to longevity

The only trailer tires Iíve been able to find with deeper treads than normal were Goodyear industrial ST tires found on all U-Haul trailers.
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Old 03-14-2013, 07:23 PM   #9
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It would appear that the ST "characteristics" are an attempt to solve problems that don't exist when LT are used on trailer applications.

I have not had a single failure with an ST tire...ever. I need to buy four tires this year and I think I will go with LT. If for no other reason than I feel better about not running at or near the speed rating of the ST for hours at a time.
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Old 03-15-2013, 11:56 AM   #10
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I have a 31' and right now it has 7.00 by 15 on it but looking to replace. My father in law has a set of brand new p225/75/15 Michelin ltx with a max load of 1840 where my tire now is max load of 2040 what's your thoughts on putting those tires on my trailer?
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Old 03-15-2013, 12:58 PM   #11
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Quote:
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I have a 31' and right now it has 7.00 by 15 on it but looking to replace. My father in law has a set of brand new p225/75/15 Michelin ltx with a max load of 1840 where my tire now is max load of 2040 what's your thoughts on putting those tires on my trailer?
I suspect that you won't find anyone here that would recommend that.

I've recently gone through the calculations of my 1976 Argosy's original tires and the replacements that are most recommended here (the Michelin LTX MS/2 P235/75/R15XL) ... and now have some understanding of why they're the recommended tires.

By the time that you've calculated the 10% derating for trailer use on your father-in-laws P225 tires, you're down to 1656lbs ... lower than a 7.00-15LT load range C tire, let alone the 7.00-15LT load range D tire that you've got on there now.

What does your owner's manual say about the tires (particularly the 6-ply or 8-ply) that you should use and the pressure? You can use that information to calculate what load the Airstream factory intended the tires to hold from the tables on Barry's Tire Tech site.
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Old 03-15-2013, 02:08 PM   #12
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Quote:
Originally Posted by Vblgrl9 View Post
I have a 31' and right now it has 7.00 by 15 on it but looking to replace. My father in law has a set of brand new p225/75/15 Michelin ltx with a max load of 1840 where my tire now is max load of 2040 what's your thoughts on putting those tires on my trailer?
My guess your trailer loaded is close to 7000lbs, without anything in the tanks.

Those tires derated for trailer use 1840-10%=1656x4=6624lbs.

So 7000lbs-700lbs tongue weight=6300bls leaves you with only 324lbs reserve for anything in the tanks (40 gallons=320lbs) and not having all the tires carrying the same weight is really pushing it past the limit (well, based on a guess).
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Old 03-15-2013, 03:18 PM   #13
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Even if my trailer weight is 4800 lbs?
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Old 03-15-2013, 03:29 PM   #14
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Quote:
Originally Posted by Vblgrl9 View Post
I have a 31' and right now it has 7.00 by 15 on it but looking to replace. My father in law has a set of brand new p225/75/15 Michelin ltx with a max load of 1840 where my tire now is max load of 2040 what's your thoughts on putting those tires on my trailer?
Are you certain of that measurement on the tires? (both the width and the weight rating.) I didn't find an LTX Michelin in that size. Are they perhaps the LTX M/S2 in a 235/75/15 with a 108 load rating, the common (and commonly-debated) 15" Michelin used on many Airstreams?
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