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  Discussion on Trailer Tires--Steel Belted vs. Bias Ply
Author Message
Member:
Terrilyn

Posted on Thursday, Mar 18, 2004 - 11:54 am:

I guess it's another case of "I'm always the last to know..." I bought my basic 2-horse BP stock trailer a year ago and all systems were in better than good condition, to include tires...basic Cooper P235/75R15 steel belted radial tires. Last weekend, I blew out one of the tires on a very pronounced (and nearly invisible!) dip in the highway...and I started asking questions as to why that may have happened. I was only pulling one horse and we weren't really loaded down. What I'm learning is that regular tires are not suitable for towing, and that bias ply tires with reinforced walls (D thickness?) are required. This is not mentioned anywhere in the article on trailering...and it's apparently an important consideration. Numerous people I know tow with steel belted tires...and don't know that they shouldn't be. I have called the usual tire stores to get all four replaced...but who carries these? RV places? Most places I've called requesting "trailer tires" don't have them large enough to replace the ones I currently have. I know I'll find them, but I'm interested in others' experiences with the two types of tires and where they have purchased the correct ones. I feel like I should have known this....am I the only one who didn't?
Member:
Eoeo

Posted on Thursday, Mar 18, 2004 - 3:08 pm:

I know what you are talking about. I have the D tires, I get them at Les Shwab which is a tire outlet all through the NW. For your 2 horse, you should be able to get by with D. I might have to go to E as I have had problems with mine getting a bulge. They are ST225/75/R15 Trailer Tires. I pull a Circle J 3H Diagonal with Dressing Area in front, and usually BIG TB Mares in it. I have the trailer in so often to check them that they have caught each one before I had a blowout. Go to reputable regular tire store and aske them their opinion. EO
Moderator:
DrO

Posted on Friday, Mar 19, 2004 - 9:28 am:

I am afraid my knowledge of tires is limited so I always follow the recomendations of the trailer manufacturer along with the suggestions of my local trailer service business. However there are steel belted radials that are designed for trailer use (Goodyears Marathon series with a D rating) and yes you should be sure that your tire is rated for the weight and speed you plan to travel. Thank you for bringing this up and this should serve as a reminder for everyone to go check the condition and pressure of their trailer tires and check to be sure your tires are rated for the job they are doing.
DrO
Member:
Terrilyn

Posted on Friday, Mar 19, 2004 - 9:49 am:

Thanks for the comments...I think the problem happens when people go to replace the tires that came on new trailers (which I assume come equipped with the D-walls or better). Seems they very often put the wrong tires on. I did learn yesterday about the steel-belted D -rated tires. I am putting four new ST225/75D15 tires on my trailer to replace the regular car tires on it now. They are about $66 apiece...glad I figured this out by blowing out a tire near home instead of hours away!
Member:
Alden

Posted on Friday, Mar 19, 2004 - 10:56 am:

The load rating just indicates the amount of weight a particular tire can handle. "E" rated tires can carry more weight than a "D" rated tire can. 3/4 ton trucks that tow and 1 ton trucks require "E" rated tires, I believe my 4 horse trailer has "D" rated radials; but I'll check today. Tire construction (radial vs bias) and rating aren't related, I would think finding a bias tire would be difficult nowadays. Radial designs provide a better ride than a bias design hence they have became the standard in passenger vehicles.

A "D" rated radial tire on a two horse should be just fine, you can find the weight capacity on the sidewall and multiply by four(tandem axles) to see the total weight capacity of your trailer (trailer, horses and gear).

I suspect your tire blow-out is a little like the beet pulp discussion and choking; tires blow from time to time. You may have picked up a nail some where or hit a rock that caused a small separation to start. Over time small separations tend to became big ones.

The biggest cause of a tire blow-out is running tires with low air pressure. Just 5-10 psi low can cause a tire to run considerably hotter than it should and heat results in tire separation. On my horse trailer I run the tires at the recommended pressure whether the trailer is empty or full.


Good day
Alden
Member:
Terrilyn

Posted on Friday, Mar 19, 2004 - 11:17 am:

Alden--
Informative post. Most of the info I've picked up on this has been anecdotal...even the guy at Northern Tool Co (they sell a lot of trailer-related stuff) seems to have given me some not-quite-accurate information, esp. regarding the bias ply vs. steel belted. I believe the point he was trying to make is that car tires that do not have thicker walls aren't ideal, and car tires are steel belted....

Who knows what really caused that tire of mine to go...could have been low pressure, heat, any number of things...when it blew, it went out in a grand way....the gash was at least 6-8 inches long! and if I didn't have another friend who'd gone through this already, I don't guess I'd be making a big fuss about it. She pulls a heavy two-horse steel Sundowner with a normal load of two big TBs. For a period of about six months, she kept blowing tires left and right when she pulled any distance...tires she had just recently put on the trailer. It was driving her crazy. She kept replacing them with the ones she had on there...until a knowledgeable repair person told her what the problem was. She hasn't blown one since replacing them all with the thicker walls. Of course when she was going through this, I paid very little attention because it had not happened to me! :-) It's different when YOU'RE the one on the side of the road!
Member:
Rose1

Posted on Friday, Mar 19, 2004 - 2:45 pm:

Trailers in my state must be inspected annually. The Dealer sold me a trailer with car tires on it. The mechanic who inspected it informed me it would not pass with out rated trailer tires.
Member:
Terrilyn

Posted on Friday, Mar 19, 2004 - 2:56 pm:

Rose--we have to have our trailers inspected here in Virginia as well. It's interesting that when I bought this trailer, it had a fresh inspection sticker on it...so either the seller switched them right before she sold it or they passed. I've heard people say that their experience with inspections varies....some places will pass regular tires and some won't. I think it just adds to the confusion and apparent lack of knowledge in this area. I'm glad to have learned something new that will benefit me in the "long haul." :-)
Member:
Rose1

Posted on Friday, Mar 19, 2004 - 3:19 pm:

Terri-
Agreed. The Dealer put an inspection sticker on the trailer he sold me with car tires on the trailer. I must believe this was not an oversight and in the future "I'll check".
Member:
Alden

Posted on Friday, Mar 19, 2004 - 3:28 pm:

Terri,

I did some snooping around the net and it turns out there are tires specifically for trailers. They can be radial or bias in construction and they are designed differently; some have "ST" or "HT" (my 2000 Exiss has Goodyear Wrangler HT load D radials). The load ratings are still A-E but their website states the "RV" tire is 10% higher standard than "LT" tires that you would put on a truck.

https://www.goodyear.com/rv/faqs/technical.html
https://www.goodyear.com/rv/faqs/load.html

Inspections are ok, but I’d rather educate myself than rely on a bureaucrat knowing.

Now everyone can run out and see if they have the proper tires! Is this a great site or what!


Good day
Alden

Alden
Member:
jhyrick

Posted on Tuesday, Apr 6, 2010 - 4:24 pm:

I just purchased a 2 horse Monarch steel trailer for local hauling. Boy does it need tires!

I found an ad "set of 4 "like new" 7.50 / 16 trailer tires - load range F - came off a 2009 trailer with about 500 miles of use.

should anything here raise a red flag??
Moderator:
DrO

Posted on Wednesday, Apr 7, 2010 - 1:07 pm:

F is at the higher end of the load range for tires designed for trailers and usually requires a 12 ply construction. But this does not tell me if they are of a suitable load rating or size for your trailer and rims. I would check the trailer's documentation and if your don't see it contact the trailer's manufacturer or a knowledgeable trailer dealer for specific recommendations. Almost as good is comparing the information of the tires on the trailer with the newer tires.
DrO
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