Switching from ST to LT tires

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Since it is impossible to find ST tires rated at higher than 65mph, would it not make sense to just go with the higher speed rated LT tires? Who the heck goes 65mph when the speed limit is 70 (75 some places)? I mean it is kind of crazy that I have 15" tires and they are only rated at 65mph!

[Bill]

The quick answer seems to be "don't do it". Special Trailer (ST) tires have different characteristics, especially in the sidewalls, than light truck (LT) tires. We should wait for our tire expert, wmtire, to chime in. But in the meantime, you might use the Search tool to uncover previous discussions on this very same topic.

Bill

[PopBeavers]

Since it is impossible to find ST tires rated at higher than 65mph, would it not make sense to just go with the higher speed rated LT tires? Who the heck goes 65mph when the speed limit is 70 (75 some places)? I mean it is kind of crazy that I have 15" tires and they are only rated at 65mph!

In California, where I live, when towing anything the speed limit is 55 mph.

If I am going to have a blow out on the trailer at an unpredictable time, like we did 2 years ago when my wife was towing for the first time, I would just be more comfortable at 55 than at 70.

I had a discussion with a TM factory rep this week at an RV show. We were discussing that I can not upgrade to 15 inch wheels because of overhead garage door clearance. It was HIS opinion that LT tires might be a good choice for me, because I am all the way up to the maximum rating of the axle.

ST tires have side walls constructed to flex in a manner to act as part of the suspension, cushioning the bounce of the trailer so it does not rattle apart. LT tires are made for heavier loads and have a stiffer sidewall. His point was that the LT might work well for someone like me that is running 3380 pounds on the axle, but for someone towing as light as possible behind a minivan then they should probably stick to ST tires.

It is my opinion that ST tires are also a better choice for a multi-axle trailer, because ST tires can tolerate scuffing better. My TM is singe axle, so this does not apply to me.

ST tires also work better than LT tires for the situation where the tires are exposed to sunlight for long periods of time and is not being towed. The tires will dry out and crack from lack of use risking premature failure. If you are towing at least once a week then LT tires, I would think, would do well with regard to sunlight. For someone like me, that only tows once a month, the LT tires may not last as long as you would think. Most of us put very few miles on each year.

I keep reading everything I can find on this topic.

[retiredgoat]

I have the 14 inch LT tires load range D on my 3326 and put 2500 miles on them so far and they look and run great. Now I know that most run the ST's but after searching some other sites and talking to a couple of businesses i.e... concrete paver installer, tree service, roofer and boat repair (he hauls up and down the coast). What I got from all of these sources was go LT and never look back. I did and so far so good.

Bob

[ShrimpBurrito]

The Kumho 857 tire has a high speed rating....I can't remember exactly what it is, but it's more than 70 MPH.

Dave

[wmtire]

Since it is impossible to find ST tires rated at higher than 65mph, would it not make sense to just go with the higher speed rated LT tires? Who the heck goes 65mph when the speed limit is 70 (75 some places)? I mean it is kind of crazy that I have 15" tires and they are only rated at 65mph!

Ok, let me see if I can muddy the water somewhat. We have been conducting an informal "great tire experiment" over the last several years. We have been doing this by trying different brands, types, etc of tires.

The first (and I think main) problem we discussed was we believed the trailers equipped with single axle 14 inch wheels/tires were already just about maxed out in their load carrying capacity........that may be leading to failures. The fellow members who had 14 inch tire/wheels were limited in what options they could find in a 14 inch tire, with a six ply rated tire being the top of the scale in an ST tire. They need a tire that could carry more load than what was readily available in ST tires.

Many members who were in this boat, switched over and are trying an Euro sized commercial applications tire that is 8 ply rated......and is kind of a hybrid between a strictly LT tire and a strictly ST tire (the differences of which PopBeavers pointed out in his post). The most significant point being, this tire is an 8 ply rated tire, thus is capable of carrying more load than any available 6 ply rated tire in a ST tire. This eight ply Euro tire is made for vans, trailers, and transports that are more popular in Europe than here in the US of A. They have smaller, more cramped cities and roads than we do....which is why they use smaller vehicles, with the 14 inch tires. This is also the same tire that Shrimpburrito and Retiredgoat are referring to as a LT tire in their posts above (ex. the Kumho 857).

It just so happens that this hybrid 14 inch Euro commercial tire is also rated for higher speeds than 65 mph........so that's an added bonus for the people who are running this tire.

The drawback is, this Euro tire is available in 14 inch tires, but not 15 inch tires.......so we have to go a different route there. Why couldn't it just be simple? Why is a penny bigger than a dime? What seems to work on solving the 14 inch problem is not going to be the same for the 15 inch ones. :eek:

In 15 inch tires, we DO have more options available in ST tires than we did in 14 inch tires. We can easily find 15 inch ST tires all the way up to a 10 ply rated tire, which helps out on the heavier trailers and gives more load carrying capacity.

The problem actually reverses itself in the ST vs LT tires in the 15 inch sizes....as far as availability goes. You will have a hard time finding a 15 inch LT tire that can carry an equal (or greater amount) of load than readily available 15 inch ST tires.

You most certainly DO NOT want to go down in load carrying capabilities, by switching to a LT tire. What benefits you may gain from being able to go faster in speed, would certainly be negated by what you lose in load carrying capacity (if you did go down). You may be able to find a 15 inch LT tire that will keep your load carrying capacity the same (but hopefully more)

Our consensus has been to try and find tires that can carry more weight safely.....because we do seem to pack our trailers pretty good with stuff. We have found 14 inch tires in the Euro sizes that can do this more than a ST tire..........but in the 15 inch tires we have found ST tires that can carry more weight than easily available LT tires.

Mhatcher, if you do decide to change your tires to LT's, can you let us know what you go with? Like I said, we are conducting a non scientific experiment between our members, trying to find the best combination.

All the best

Bobby

[PopBeavers]

Another issue is China.

From what I have read on various forums, Marathons used to be made in the US, then China, but are now back to the Us. Some people believe that the Chinese Marathon's had a high failure rate and that this has been solved by moving production back to the US.

There seems to be a love/hate view of the Goodyear Marathon's. It seems to be a unanimous hate for the Carlisle's.

I have not seen any significant reference to other brands. I am presently running Tow Master ST 14 inch. I may replace them after 3 years.

[Al-n-Sue]

I'll be putting new 15" tires on my 3124KB this spring and Discount Tire is my preferred dealer. They carry Marathons and Carlisle. The Marathons come in a class C rating, but the Carlisles are available in C, D or E ratings - if I'm reading the charts right. Prices are within $10 each, so that is not really a factor. I couldn't find specific weight ratings, but then I haven't done extensive reseach either.

I've heard, despite all the bad press, that Carlisle's are now made in the US and their durability is much better, but I can't confirm that. Does anyone have definitive evidence one way or the other?

I'd like the higher rated tires - my TM weights in at over 4200 lbs - but I don't want to deal with problems either. And I have a couple of lengthy trips planned this year.

Any advice accepted.
Thanks.
Alan

[Bill]

Hmmm. According to the Discount Tire website, the 15" Marathons are available in size ST205/75R-15/C or size ST225/75R-15/D1. I'm not sure what "D1" means, as opposed to "D". Any thoughts, Bobby?

Weight ratings can be found on the Goodyear website http://www.goodyear.com/rv/products/marathon.html

Bill

[wmtire]

Hmmm. According to the Discount Tire website, the 15" Marathons are available in size ST205/75R-15/C or size ST225/75R-15/D1. I'm not sure what "D1" means, as opposed to "D". Any thoughts, Bobby?



Hmmm, never seen that before. Could possibly be just a typo, put in by their sites webpage designer.


EDIT: I was talking awhile ago to a friend of mine who is a bigtime Goodyear dealer. I went ahead and asked him this question, and he also said he had never heard of it.

[Al-n-Sue]

Bill - the weight ratings chart is helpful. It says I need the D rating to get the weight capacity that I would be comfortable with.

I looked at the Discount Tire site again and still don't see the listing for the ST225 size - I even changed locatoins thinking that it might be an availability issue here that was the problem. But even picking L.A. area only showed the ST205.

I may have to call the dealer here to see if he can get the D rated ones.

Thanks for the feedback.
Alan

[wmtire]

I looked at the Discount Tire site again and still don't see the listing for the ST225 size - I even changed locatoins thinking that it might be an availability issue here that was the problem. But even picking L.A. area only showed the ST205.

I may have to call the dealer here to see if he can get the D rated ones.

Thanks for the feedback.
Alan

Alan, I am seeing the same Marathon tires as Bill when I use my home zip. I went ahead and put a California zipcode in, and THEN am seeing only the one tire you are seeing. So Discount may not possibly have it in your area. If you are just wanting to look at the tire (Load Range D), then you might can try my zipcode of 71291.....or even look at Tire Racks page below.

http://www.tirerack.com/tires/Sizes.jsp?make=Goodyear&model=Marathon+Radial

[Al-n-Sue]

Thanks Bobby - I called the dealer here and found tha the can get the load range D tire, but he said they are more pricey - $124 vs $106 for the C. He said he was selling a lot of the Carlisle tires in the E load range which is a 2830 lb rating ($101). He also said all his trailer tires - even the Marathons - were still coming from China! He thinks that will be changing due to tariffs, but for now, his last load was from China. And he thinks the Marathons are over priced and not as good as the Carlisle.

The Carlisle with the E rating runs at 80 psi - so it seems to me that it is stout enough to handle my 4250 lb TM. I know most/all the reviews I've read on Carlisle say they are terrible. But I wonder how many are running C or D ratings and are not adequate for the rig?

Interested in other comments on the Carlisle.

Alan

[Redhawk]

I too am getting ready to replace my tires, I'm in Colorado Springs 80919, and was looking at the Maxxis 15" 225 Load range D (they also have an E) the Discount Tire web site showed a price of $119. for the D rated tire. Not meaning to confuse the issue.

All I know about the Maxxis is that I run their tires on my ATV and they are tough as nails. Does anyone know the bolt pattern i should ask for when ordering the wheels?

[Keith Wire]

Hi Redhawk,

Our Modorator, Bill, posted that information a while back.

You can find it here (http://www.trailmanorowners.com/forum/showthread.php?p=60851&highlight=bolt+pattern#post60851).

Keith

[Gwenzilla]

I believe its a 5 on 4-1/2" bolt pattern (5-114.3mm / 5-4.5")- that's what was on my 2619.

[brulaz]

Getting back to what the OP was concerned about: 65 mph max, I found the following in the "Goodyear (Marathon) Recreational Vehicle Tire and Care Guide". Has anybody tried raising their tire pressure to 75psi (if your wheel allows it) so they can go 75 mph?

I will never try it. 65 mph max. is fine by me. Just curious.

BEGIN QUOTE
IMPORTANT OPERATING INFORMATION
Industry standards dictate that tires with the ST (Special Trailer) designation are speed restricted to 65 mph under normal inflation and load conditions, unless a different speed restriction is indicated on the sidewall of the tire. Based on industry standards, if tires with the ST designation are used at speeds between 66 and 75 mph, it is necessary to increase the cold inflation pressures by 10 psi above the recommended pressure for the load.
• Do not exceed the maximum pressure for the wheel.
• If the maximum pressure for the wheel prohibits the increase of air pressure, then the maximum speed must be restricted to 65 mph.
• The cold inflation pressure must not exceed 10 psi beyond the inflation specified for the maximum load of the tire.
END QUOTE

Another quote to explain why 65 mph is fine by me:

BEGIN QUOTE
Effects of Higher Speeds
• When traveling at 65 mph vs. 55 mph, tires will experience a 15% tread life penalty (30% at 75 mph)
• Trucking fleets report fuel economy losses of about one mpg for every ten mph over 55 mph (a 15% loss)
• Longer breaking distances (SAFETY ISSUE!)
• Reduced handling ability (SAFETY ISSUE!)
• More fuel stops due to reduced fuel economy
• Tire load-carrying capability decreases as speed increases
END QUOTE

[Bill]

We've talked about it. It seems that no one is positively sure what those words mean. For one thing, the words "10 psi above the recommended pressure for the load" seems to suggest that you can/should raise the pressure beyond the MAX PRESSURE stated on the sidewall. I'm not comfortable with that, for sure. Or perhaps it means that if the tire is so lightly loaded that you are running at 55 psi, then you can increase the pressure to 65 psi (still within the sidewall rating) and run at 75 mph if you maintain the same very light load. It is just a bit ambiguous to me, anyway. And no one I know runs at a very light load.

And then, the words "Tire load-carrying capability decreases as speed increases" tell me that the tire will carry less if you are running fast - but it doesn't tell me how much less. Is it less than the "very light load" mentioned above?

Bill

[brulaz]

• Tire load-carrying capability decreases as speed increases

Yes, I was wondering just what that meant. Pretty ambiguous.

Thanks,
Bruce