Trailer tires VS Truck tires

[Edd505]

Originally Posted by FastEagle

If you are, in fact, a retailer of tires, you should read the following link, top to bottom. It is provided by those that actually establish tire industry standards.

https://www.ustires.org/sites/defaul...TruckTires.pdf

Not a word of don't use LT's in place of ST's, it does talk of P to LT.

[FastEagle]

Originally Posted by Edd505

Not a word of don't use LT's in place of ST's, it does talk of P to LT.

When you apply the proper tire nomenclature - Designated Size - the rest is self evident.

Look at "tire size" on page 21 of the reference. Manual year is not important because that tire statement is there because of a NHTSA mandate.

https://www.kz-rv.com/owners-manuals...ers-Manual.pdf

[Mtn. Lion]

Originally Posted by FastEagle

When you apply the proper tire nomenclature - Designated Size - the rest is self evident.

Look at "tire size" on page 21 of the reference. Manual year is not important because that tire statement is there because of a NHTSA mandate.

https://www.kz-rv.com/owners-manuals...ers-Manual.pdf

Originally Posted by ustires.org CareAndService_PassengerAndLightTruckTires.pdf

Tires specifically designed for travel trailer use in highway service have an “ST” molded on the tire sidewall such as ST225/75R15. Also see Chapter 1 “Basic Tire Information.” ST tires have different load capacity characteristics. Therefore, ST tires should not be replaced with any other type tire.

The doc does say ST tires should not be replaced with any other type of tire because of its load characteristics.

So there isn't a standard sizing for both market segments (LT and ST). But that can be worked around through conversions to get the right size LT tire to fit, if the given LT size is available at the proper load and speed ratings.

Inquiring minds want to know why there is a unique ST market segment. What makes the ST special other than being dumbed down and cheap.

[FastEagle]

OK, I’ll explain with a very short MSG. Technically it’s a misapplication to replace a vehicle certified OE tire that is an ST with anything other than ST.

UNLESS, the vehicle manufacturer has offered optional designated sizes.

Officially a tire’s size is actually described as “designated size”. And that’s how the FMVSS refers to them in their instructions to the vehicle manufacturer. This is a designated size; ST235/80R16, nothing more and nothing less. When that designated size is displayed on the vehicle certification label it would be a misapplication to use any tire with a different prefix.

Hey, I’m just saying what happens before the consumer takes control of the trailer. It’s their responsibility to stay inside of the safety parameters. Is a misapplication a safety factor?

[Grandpa5x]

My last 5th wheel came with LT tires, I was very happy with that as I’d had ST tires on my previous trailers and always had trouble after the first two years. You won’t regret going with LT. Your previous experience with six ply tires on your truck was do to under load rating. For your trailer determine the load rating you need and go one size above and you’ll never hav to worry about them again.

[outlaw5067]

All I know is that I got tired of the ST blowouts in the Southern summer heat and switched to Michelin XPS RIB LT tires. The 5W pulled better and the tires stayed cooler.

[Bus Man]

You might want to browse www.boarwheel.com. Watch some of their videos and see if they make sense to you. I have them on my Rushmore 5th wheel 7k tandem axle & 15500 gvwr. When you see the video showing a cutaway section of a ST tire compared to a 19.5 tire it will shock you.

[Tireman9]

Originally Posted by Mtn. Lion

The doc does say ST tires should not be replaced with any other type of tire because of its load characteristics.

So there isn't a standard sizing for both market segments (LT and ST). But that can be worked around through conversions to get the right size LT tire to fit, if the given LT size is available at the proper load and speed ratings.

Inquiring minds want to know why there is a unique ST market segment. What makes the ST special other than being dumbed down and cheap.

In the'60's RV trailers were mostly smaller <25' single axle towed behind a car or smaller P/U. RV companies wanted cheaper tires. Speed limits were lower so GY, over the objections of other tire companies came up with "Special Trailer" tires with a 65 mph max speed. This speed reduction and decreased tred depth theoretically offset the increased load capacity when compared to the same dimension LT type tires.


In 2002 after the Explorer fiasco new tougher standards were implimented by DOT. RV mag fought to keep the test requirements for ST type the same as they were in 1968 while P type and LT type had to meet new tougher standards.
In 2017 China was accused of "dumping" cheep tires of all types into the US market. Trade restrictions (not tire standards) identified speed rated tires as not having to pay the import duty. Almost overnight all ST type tires became speed rated. The SAE test for speed rating is stated as a "passenger car tire test" but was applied to ST type. It only requires tires to run for 30 minutes at the stated speed and not come apart at 30 minutes.


Back to the OP. "Dry weight" is of no value. GAVWR is almost useless as it is well documented that a majority of RVs have tires and /or axle in overload. The only weight number that really means anything is the actual scale reading for each tire as weight is almost never exactly split 50/50 acle to axle or side to side. Some big RV have been found to 1,000# or more out of balance.


Reserve load is the extra load capacity above the actual load. Cars and P/U have reserve load on 20 to 40% while RVs have 0% to maybe 8%. That is a MAJOR reason for the difference in durability. There is also the shear forces seen in trailers that can be 24% higher than an identically loaded tire on a motor vehicle. You see thing when backing into a parking spot but the shear is always there in every curve or turn.


I have covered the above in numerous posts on my blog if you care to learn the facts from an actual tire design engineer and court recognized "expert".


Or you can listen to the guy in the camping space next door or the salesman at "Billy Jo Bob's Cheep tire and Bait Emporium".

[RoadrunnerII]

Originally Posted by Tireman9

In the'60's RV trailers were mostly smaller <25' single axle towed behind a car or smaller P/U. RV companies wanted cheaper tires. Speed limits were lower so GY, over the objections of other tire companies came up with "Special Trailer" tires with a 65 mph max speed. This speed reduction and decreased tred depth theoretically offset the increased load capacity when compared to the same dimension LT type tires.


In 2002 after the Explorer fiasco new tougher standards were implimented by DOT. RV mag fought to keep the test requirements for ST type the same as they were in 1968 while P type and LT type had to meet new tougher standards.
In 2017 China was accused of "dumping" cheep tires of all types into the US market. Trade restrictions (not tire standards) identified speed rated tires as not having to pay the import duty. Almost overnight all ST type tires became speed rated. The SAE test for speed rating is stated as a "passenger car tire test" but was applied to ST type. It only requires tires to run for 30 minutes at the stated speed and not come apart at 30 minutes.


Back to the OP. "Dry weight" is of no value. GAVWR is almost useless as it is well documented that a majority of RVs have tires and /or axle in overload. The only weight number that really means anything is the actual scale reading for each tire as weight is almost never exactly split 50/50 acle to axle or side to side. Some big RV have been found to 1,000# or more out of balance.


Reserve load is the extra load capacity above the actual load. Cars and P/U have reserve load on 20 to 40% while RVs have 0% to maybe 8%. That is a MAJOR reason for the difference in durability. There is also the shear forces seen in trailers that can be 24% higher than an identically loaded tire on a motor vehicle. You see thing when backing into a parking spot but the shear is always there in every curve or turn.


I have covered the above in numerous posts on my blog if you care to learn the facts from an actual tire design engineer and court recognized "expert".


Or you can listen to the guy in the camping space next door or the salesman at "Billy Jo Bob's Cheep tire and Bait Emporium".

Tireman9 speaks the truth in my humble opinion. I chose to pull Endurance ST tire's off my brand new trailer and put Michelin LT Rib all position rated tires on it. Yes I understand and researched what I was doing. The rib tires have a slightly lower carrying capacity but are still not overloaded on my particular trailer. I have weighed it to make sure!
The gy endurance tires have for the most part shown to be a good tire from my research but where brand new on the market. After the china bomb marathons I was being cautious.
You cannot, should not and are very foolish to change tire types without doing your homework. My research showed they where appropriate for my application.
I feel the rib tires are a better fit for my rig and will replace with rib tires when the time comes
Just my 1/2 cent of common sense.

RoadrunnerII

[T12]

On my class A I run rollers in the front and grips in the back. Rollers have more rib style tred and promote better gas mileage. Grips have somewhat of a more block looking tired pattern. The reason for grips comes in handy when road conditions are slick. The rollers aren't the best rollers because they allow water to channel out from the center of the tire which reduces the chance of hydro planing.
Trailer tires are usually designed more for rolling as opposed to traction. The party that sold us our rig had put trailer tires on the rear. It didn't take long before the tred came loose. We replaced them before we anywhere with it.
The amount of ply a tire needs to be is determined by the weight they need to carry. If the tires on your rig were put on by the manufacturer then most likely they are most likely adequate for that rig. However, if you want to know for sure load up your rig with everything you would take on a trip including filling up your freshwater tank and go down to your local truck scale. Find a tire dealer that will sell you what you need as opposed to making a buck. Knowing the actual weight the tire will carry will help the tire shop sell you the right tire.
The amount of time a tire lasts depends a lot on how and where you drive along with keeping them aired up properly. Another factor is the compound the are made from. Look at the tread wear rating after you do research on how the rating works. It will make you a better consumer.

[consolenut]

Most ST tires are speed rated to 60-65mph. Dont exceed it. Slow down your in am RV yoir not in a hurry. If you have a heavyweight 5ver like mine ST are the only tires to use. If you have a lighweight you might get away with and LT Difference is you start back and turning and the LT tire may rip the sidewall or worse break the bead on the rim. The sidewalls of and ST tire are much different. i went from whimpy 16's 3340 a tire to 17.5 at 6005 a tire load ratings. Find an LT Tire what will have thay load rating lol. Pick the tire for the job dont expect and LT to do an ST job. Any good tire tech will tell you same thing. Oh one more thing get your ST tires balanced and if you can get then Tru'd too.

[FastEagle]

Originally Posted by consolenut

Most ST tires are speed rated to 60-65mph.

The only ST tire I can find on todays market with a speed letter ("L") below 75 MPH is the Maxxis.

Many of the 17.5" low platform trailer tires with a European design have a speed letter "J" = 62 MPH.

[BSHGTO]

So much miss information here it`s all most scary.The side wall construction of an ST tire is not the same as a LT tire and it`s use on trailer is not recommended on a trailer. Oh yes it will go down the road straight and carry the load but it`s the special times in a tires life that it will fail. Really people if a LT tire was just as good with the curbing, twisting, grinding them in place why would they even make a ST tire. Yes I know some old people will say "been doing it for 20 years and nar a problem" but you have doing it wrong for 20 years, sport. But I know cost is always a good way to talk your self into something. Go read on how and of what a Sailun tire is made of, under what conditions and for what application and the construction details will be telling. Yeh, but I know don`t have the time the wife wants me to help her with the dishes so I`ll just buy these tires there rated for the same weight. The tire my dually came with are rated for the same weight as my trailer tire but I would never think they could go on the trailer. Just stand on the side wall of your special truck tire then stand on the side wall of a Sailun ST tire the truck tire will collapse the ST tire will hold your weight up. Or just weigh your LT tire then weigh the ST tire it will be 30lbs heavier. So you think they put extra weight in them for what?, consumer comparison or because of extreme construction to take a beating and keep on ticking ( remember that statement? ) You`ll see why this post is a bunch of whooey if you stop doing dishes and do some research.

[BSHGTO]

Originally Posted by FastEagle

The only ST tire I can find on todays market with a speed letter ("L") below 75 MPH is the Maxxis.

Many of the 17.5" low platform trailer tires with a European design have a speed letter "J" = 62 MPH.

Not so, miss in formation with a slant to what you want to believe. Mine are rated to 75 MPH (Sailun ST) You shoudn`t be driving that fast any way pulling a camper. Maxxis is an inferior tire with many many ruined weekends for people with blow outs and damage, but there cheap.