"trailer" tires

[erikgreen]

Just a quick note for new trailer owners, because I got fooled by this.

I bought my old boat trailer with four tires on it (dual axle) and noted that all four were ok for the drive home, but two were rotten and should be replaced fairly soon.

I got the trailer home ok, and looked up some information on the tires. All of them were labeled "STXXXX" on the side wall, which according to what I read was the definition for "Special Trailer", IE the right tires. Two of the tires were goodyear and two were (I think) bridgestone.

I went to buy trailer tires last weekend and found out that the ST was just a model or brand marker. All four tires turned out to be automotive tires, ST24575R14... probably many of you would have known that from the size, but I didn't.

Anyway, I ended up replacing two of the auto tires (budget crunch) with real carlisle trailer tires, and it made a HUGE difference in ride.... much less sway on the trailer, it tracks the truck much better.

Anyway my lesson learned was that just because your tires say "ST" doesn't mean they're trailer tires.

Erik

 

[tashasdaddy]

Re: "trailer" tires

you are very correct, that was one of their advertising gimmicks, just like Wrangler on the tire. ST for the trailer tire is usually in the small print on the tire.

 

[Silvertip]

Re: "trailer" tires

Are you sure you didn't mistake "LT" for "ST". The tipoff for trailer tires is the inflation pressure. Trailer tires (depending on size) will have inflation pressures that start at 50 PSI and go up to 90 PSI (as for my 20.5x8x10, 10 ply pontoon trailer tires). LT (light truck) tires would be less than 50 pounds and auto tires will be around 36 PSI. I wish you would have photographed that designation because ST, LT, and P (Passenger) are all "application" designators and are an integral part of current tire specifications. If these were very old tires I suppose they could have sneaked in under the radar but I have never seen an auto tire marked as ST and marketed as a Special Trailer tire. Seems to me that would leave a huge hole in a legal dispute. If the ST was separated from the rest of the size designator I could see where some confusion or deception might be possible. But if the ST was the same size and directly in front of the tire size it should have been a trailer tire.

 

[triumphrick]

Re: "trailer" tires

Went to Sam's club for my tires. Didn't have them is stock so I suggested a comparable auto tire. Guy said he would get fired for doing it. Left there and found a local tire store who had what I needed in a trailer tire. I bought them but asked him if he would put auto tires on and said he** no, I can't afford to lose my job!
Seems like we had a couple of dealers who knew it was nearly illegal to do so.

 

[Titanium48]

Re: "trailer" tires

Not all LT tires have a 50 psi max inflation pressure. Many of the high load rating tires used on 3/4 ton and heavier trucks have 65 or 80 psi maximum pressures. Of course, those are for 16 inch or larger wheels.

 

[j_martin]

Re: "trailer" tires

Tires of many sizes can be had with different load ratings and inflation pressures. The higher load ratings take higher air pressure.

My boat trailer wheels have a max pressure of 35 psi, so there is no capacity compromise to go to a good automotive tire of the same capacity. That's what I did with the tire man's aproval. (Steve has a million dollar business just dealing with tires of all kinds.)

BTW, if you use a heavier tire and more air pressure than the wheel is designed for, it can tear, usually at the bead, and it will do so suddenly and violently at the most inoportune time. (Murphy's Law)

The main thing is that most folks don't realize that their boat gains considerable weight when you put in fuel, the fishing gear, and all the camping and play stuff that just seems to fit in that nice open container. Guess what your boat weighs and be sure the tires are good for at least 50% more, and you'll be fine.

hope it helps
John

 

[erikgreen]

Re: "trailer" tires

Are you sure you didn't mistake "LT" for "ST". The tipoff for trailer tires is the inflation pressure. Trailer tires (depending on size) will have inflation pressures that start at 50 PSI and go up to 90 PSI (as for my 20.5x8x10, 10 ply pontoon trailer tires). LT (light truck) tires would be less than 50 pounds and auto tires will be around 36 PSI. I wish you would have photographed that designation because ST, LT, and P (Passenger) are all "application" designators and are an integral part of current tire specifications. If these were very old tires I suppose they could have sneaked in under the radar but I have never seen an auto tire marked as ST and marketed as a Special Trailer tire. Seems to me that would leave a huge hole in a legal dispute. If the ST was separated from the rest of the size designator I could see where some confusion or deception might be possible. But if the ST was the same size and directly in front of the tire size it should have been a trailer tire.

I'll take some pics tonight. If I remember right it was in the raised white lettering AND the size.

Erik

 

[Silvertip]

Re: "trailer" tires

Are your "35psi" wheels automotive wheels that were installed as original equipment on the trailer or were they added by you or a previous owner. Trailer wheels have zero offset meaning the hub surface is directly in the middle of the wheel or directly in the center of the tread area. If a wheel center is set toward the spring it is very likely a rear wheel drive auto wheel. If the wheel center is toward the outside of the wheel it is likely a front wheel drive auto wheel and not a good choice for a trailer. I've not seen a zero offset trailer wheel that has a 35PSI maximum rating as it would not be suitable for 90% of the trailer applications where 50PSI and up are generally the rule.

 

[MrBigStuff]

Re: "trailer" tires

My boat trailer wheels have a max pressure of 35 psi, so there is no capacity compromise to go to a good automotive tire of the same capacity. That's what I did with the tire man's aproval. (Steve has a million dollar business just dealing with tires of all kinds.) hope it helps
John

The weight capacity is only ONE factor to consider. Trailer tires are designed to handle sway, something a car does not have to contend with. They are also better designed to handle HEAT which can be significant in a trailer tire and is very detrimental to an automotive tire. Your tire man Steve is a fool to risk his multi-million dollar business so that some of his customers can save a couple of dollars...

 

[Pony]

Re: "trailer" tires

The weight capacity is only ONE factor to consider. Trailer tires are designed to handle sway, something a car does not have to contend with. They are also better designed to handle HEAT which can be significant in a trailer tire and is very detrimental to an automotive tire. Your tire man Steve is a fool to risk his multi-million dollar business so that some of his customers can save a couple of dollars...

DITTO!

The sidewalls are engineered to do completely different things.

 

[j_martin]

Re: "trailer" tires

Original aluminum wheels on a Tracker boat trailer. Larger diameter wheels, like 14 and 15 inch on a light trailer are generally lower pressure. You need 90 psi to hold up a ton and a half trailer on 12 inch "trailer" tires.

You obviously have never ridden with me if you think that trailer tires have to contend with more side force than car tires.

My tire man has kept me in good rubber on everything from wheel barrows to heavy dump trucks for 30 years. I'm gonna believe him.

I'm outa here.........

John

 

[reelfishin]

Re: "trailer" tires

I can see the need for 'trailer' tires on a trailer that carries any substantial load but many of us are pulling boats light enough to carry. The trailer and boat don't come close to taxing the sidewalls or load capacity of any tire.

I have a 14' trailer and a 12' v hull that weighs under 500lbs total, the tires are 13" passenger tires on galvanized trailer rims. I had trailer tires, they rode so hard they were denting the boat on the bunks. The springs are 800lb rated, the lightest I could get, and the original tires were 35psi A78 13 ST Marathons.
I switched to the lightest passenger tire I could find and the whole thing rides much better and there's no more bouncing. The only way I could soften the ride with the trailer tires was to run about 15 psi of air, and that just isn't safe. I run 3 miles to the lake, at an average of 30 mph or less. In my case, the softer tires did the trick.

When it comes to trailer tires around here, they are down right hard to come by. No one stocks them and they are three time the price of regular tires.
I got a price of $103 per tire for two B78 13ST tires for my other boat trailer, I ended up ordering them online, as two new wheels and tires for a little more than the cost of one tire locally. For local running, where the trailer will see lots of off road or sea shell paved roads, I prefer bias ply tires but they're getting tough to find. I've cut several sidewalls on sticks and rocks on radial tires with softer sidewalls.

I've never worn out a set of trailer tires, they usually rot off or the rim rusts away first. I often just toss the rim and tire for this reason, saltwater eats the rims here pretty fast, galvanized or not.

What did they use years ago? I don't remember there being trailer tires 30 years ago and have never come across an older trailer with ST tires, mostly just bias ply passenger or truck tires.

 

[Silvertip]

Re: "trailer" tires

Years ago cars had wooden wheels too and we wouldn't think of using them today. Progress marches on and so will the car tire/trailer tire discussion. Trailers from inception to today have changed very little. They don't have shock absorbers (generally) and are generally loaded pretty close to their GVWR. Hence the tires and springs do the "ride" work. Soft sidewalls and lower inflation pressure of car tires simply is not a good combination on that type of trailer. Yes -- there are exceptions as in Reelfishin's case.

 

[reelfishin]

Re: "trailer" tires

Years ago cars had wooden wheels too and we wouldn't think of using them today. Progress marches on and so will the car tire/trailer tire discussion. Trailers from inception to today have changed very little. They don't have shock absorbers (generally) and are generally loaded pretty close to their GVWR. Hence the tires and springs do the "ride" work. Soft sidewalls and lower inflation pressure of car tires simply is not a good combination on that type of trailer. Yes -- there are exceptions as in Reelfishin's case.

You brought up an important point about trailers not generally using shocks.
I have several cut off pickup trucks that I use as utility trailers and two older Holesclaw trailers with quad shocks and coil spring suspension.

I put a set of trailer tires on one of the pickup bed trailers, they wore out in a matter of a few months or about 5000 miles, while standard truck tires last and last. The trailer also rode harsh and bucked and jerked the truck really bad, but with 'passenger' tires it rides fine and tracks straight. It tows better with old time bias ply tires and about 35psi than it does with higher pressure trailer tires. I've had it filled to overflow with dirt and rocks before and it survives, if it ever broke, I'd most likely drag it straight to the junk yard.
It's probably worth more in scrap today than as a trailer.

The vintage Holesclaw trailer uses strange wheels, they're 8" but have no lugs, they bearings are in the rim. The tires are plain 8" trailer tires. That trailer rides great, it's one of those trailers that you don't even notice behind you, whether loaded or empty. It's also a trailer that tends to wear tires faster than most. The wheels are at zero toe in and there's no camber at all.
It's just a very flexible frame and axle and the axle flexes in and out of alignment too much at todays highway speeds. Its fine when used locally at lower speeds on smooth roads. It also doesn't cradle the boat very well.

I see a lot of boats sold on trailers far too heavy for their weight. Especially aluminum boats.

 

[erikgreen]

Re: "trailer" tires

I'll take some pics tonight. If I remember right it was in the raised white lettering AND the size.

Erik

Since I've been lazy about getting the pics up, here's a summary: The tires I removed, one had "ST" in the size and on the raised white letters, the other one it was only in the raised white letters. The ones still on the trailer are matched auto tires :\ P245 75/R14, along with (rear axle) two new ST205 75/R14.

Erik

 

[guy74]

Re: "trailer" tires

Here is some interesting reading about trailer tires.
http://www.subaru.com/owners/carcar...91903trailer_safety&navid=TRAILER-TIRE_SAFETY

 

[SuperNova]

Re: "trailer" tires

Here is some interesting reading about trailer tires.
http://www.subaru.com/owners/carcar...91903trailer_safety&navid=TRAILER-TIRE_SAFETY

That is a good site to dispel a lot of the mystery surrounding trailer tires. I have seen more discussion on this and other forums relating to trailer versus automotive type tires and 99% of what I've seen is inaccurate; some of it ridiculously so. Even quite a few posts in this thread made me laugh at the level of ignorance purporting to be "law". Good post, guy74.
--
Stan

 

[guy74]

Re: "trailer" tires

Went to Sam's club for my tires. Didn't have them is stock so I suggested a comparable auto tire. Guy said he would get fired for doing it. Left there and found a local tire store who had what I needed in a trailer tire. I bought them but asked him if he would put auto tires on and said he** no, I can't afford to lose my job!
Seems like we had a couple of dealers who knew it was nearly illegal to do so.

As far as the legallity of running passenger tires on a trailer, I can find no regulations (state, or federal) on the subject. Please post links to any that you can find.

 

[reelfishin]

Re: "trailer" tires

I truly doubt that there are any laws on the books requiring "trailer" specific rated tires on trailers, if so, what about the thousands of cut-off pickup bed trailers running around?
You will find weight limits on trailers and certainly load limits pertaining to tires and trailers. A lesser tire will lower the capacity of a trailer to that of the sum of it's tires. A trailer tire generally can carry far more weight than a standard passenger car tire.
I don't think the safety factor is as great as the fuel economy factor so long as you stay within the tire's rated maximum carrying capacity.
I've seen first hand the difference on larger trailers between car tires and proper trailer tires, but a lot has to do with the amount of air a true trailer tire can take.
I bought a 26' enclosed trailer about 200 miles from home a few years ago, I towed it home with a half ton truck with the proper hitch and brake set up. It towed like ten tons of bricks behind me. The last owner had put on four new el cheapo Chinese radials with a 35 psi max. I bought it assuming I'd have to buy tires anyhow, so it didn't matter that way, but I was shocked that after swapping them for the proper trailer tires with a 70 psi max pressure, that trailer pulled and towed like a dream. It barely affected the truck at all. The tires that came on it were 760lb rated 205/70-14R made in China specials, I replaced them with a set of 205/75-14R ST Marathons.
I eventually found a set of bias ply tires that worked even better since they held weight better, but the bias ply tires don't wear near as well as the radials. Bias ply tires do seem to pull easier though for some reason.
I've had concerns with several trailers that I've fixed by going back to old style bias ply tires. I have two trailers which I had towed home, loved the way they towed, so I replaced the tires with all new radial trailer tires and ended up with a trailer that bucked and jerked so bad I hated to tow it. I had borrowed a set of those new tires from one of those trailers one day to go pickup another trailer far from home and put the original rims and tires back on. The next day, I used the trailer with the old tires and it again towed perfect, after that, I tossed the tires on two other trailers and solved the bucking issue. I'm not sure why but I think it's got a lot to do with rolling resistance. Neither trailers are very heavy, nor are the boats, but with radial tires they buck and tug at the truck like mad, with bias ply tires, you can't feel the trailer at all. Up until then, I would have never guessed that the type of tire could possible make that much of a difference, even on an empty trailer.

I've also found that on a tandem trailer, too much traction can be a bad thing when pulling with a smaller truck, especially when trying to back up around a corner on pavement. The tighter the tread pattern the harder to maneuver. Larger lugged tires maneuver much nicer on tight turns. When backing my 25' trailer up the drive and around the house, I end up burning the trucks tires just to push the trailer at a 45 degree turn with some tires. I ended up spreading sand in the area where the trailer has to turn or pivot to make the turn. I put on a set of no name large lug trailer tires at first due to the fact that they were cheap, but it turned out that the huge lugs on those tires lessened traction enough to make the trailer maneuverable. (Less rubber in contact with the pavement). The trailer has no brakes, so traction on the road isn't a concern and it's really only used to pull and dry dock that boat once a year, so those tires will rot away before they wear out.

 

[dingbat]

Re: "trailer" tires

Are your "35psi" wheels automotive wheels that were installed as original equipment on the trailer or were they added by you or a previous owner. Trailer wheels have zero offset meaning the hub surface is directly in the middle of the wheel or directly in the center of the tread area. If a wheel center is set toward the spring it is very likely a rear wheel drive auto wheel. If the wheel center is toward the outside of the wheel it is likely a front wheel drive auto wheel and not a good choice for a trailer. I've not seen a zero offset trailer wheel that has a 35PSI maximum rating as it would not be suitable for 90% of the trailer applications where 50PSI and up are generally the rule.

I find this coment interesting.

I'm running 4- Cooper ST 205-75R14 Special Trailer radials on a Tandem Loadrite trailer. The sidewall states a load rating of #1760 with a max. inflation rating of 35 psi. The hubs are slotted galvanized hubs that came stock on the trailer so I got to beleive that they're "trailer" hubs.

Any ideas?

http://coopertire.com/html/products...om_trailer&LanguageId=1&tiretype=S&sorttype=T