ST vs LT tires

The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.

flagstaff

Member
Joined
Mar 7, 2012
Posts
16
I have seen some tire threads that will sometimes refer to using LT tires on a trailer.

What's the difference and pros and cons?
 

donn

Well-known member
Joined
Nov 8, 2009
Posts
4,502
Man, this has been beat to death over the past six months.
Basically ST tires are all made off shore, typically China and have a very high rate of premature catastrophic failures.  LT tires generally are more readily available at decent prices, have a better speed rating, 99 vs 65MPH, do not have the high failure rates.  For more information use the search function above.
 

Gary RV_Wizard

Site Team
Joined
Feb 2, 2005
Posts
73,974
Location
At our Silver Springs FL home
ST tires are rated for trailers only. The side walls are stiff, making them unsuitable for use as steer axle tires but good for trailers. The shortcoming is that they are limited to 65 mph and many of them are of mediocre quality. There are a few good ones - Maxxis is one of te better brands.

LT can get a bit confusing because there are two conflicting uses of the LT designation. One is for High Flotation tires, which are very low pressure and used for offroad mud and sand. Never put those on any on-road vehicle.  The more common LT designation is Light Truck and is intended for pick-up trucks. They have relatively strong sidewalls but still suitable for steering. They also work fine for trailer axles and there are often a wider range of sizes and load ranges available - and at more competitive prices too. LT tires will have a minimum speed rating of 75 mph and some may be rated higher.
 

FastEagle

Well-known member
Joined
Jan 12, 2010
Posts
595
Other than the speed restriction that Gary has pointed out there is the wide difference in load capacity ratings between the ST and LT tire designs. For instance, the LT235/85R16E has a load capacity of 3042# at 80 psi whereas the ST235/85R16E has a load capacity of 3640# at 80 psi.

To stay within industry standards when using LT tires to replace ST tires becomes very difficult.

FastEagle 
 

donn

Well-known member
Joined
Nov 8, 2009
Posts
4,502
FastEagle said:
Other than the speed restriction that Gary has pointed out there is the wide difference in load capacity ratings between the ST and LT tire designs. For instance, the LT235/85R16E has a load capacity of 3042# at 80 psi whereas the ST235/85R16E has a load capacity of 3640# at 80 psi.

To stay within industry standards when using LT tires to replace ST tires becomes very difficult.

FastEagle

Whats your latest count on ST tire failures FE???
 

lavarock1210

Well-known member
Joined
Nov 7, 2010
Posts
446
donn said:
Whats your latest count on ST tire failures FE???
I have had many LT tire failures.  Close to 5 as far as I can remember.  I have never had a ST tire failure. 
As for trailer use I suspect there is close to a 100 to 1 ratio of ST tires being used to LT tires.  Thus with trailer tire failures I would say a 100 to 1 ratio would be expected.
 

COMer

Well-known member
Joined
Aug 25, 2009
Posts
1,663
What size are your tires?  When I replaced my 15" tires this year, I was not able to find any LT tires made in that size.  At least not where I was which was in FL.  I found some load range E tires in my size and am very happy with them.  I also found some dealers who said that their company policy would not allow them to put LT tires on a trailer.  That was Sam's and they were adamant.  Not sure if that was a nationwide policy or just in FL.
 

Foto-n-T

Well-known member
Joined
Jan 1, 2012
Posts
1,121
Location
Cody, Wyoming - Sometimes
I've used both LT & ST tires.  The main reason I purchased LT's was that the tread depth is slightly greater and since we travel a lot my reasoning was that they wouldn't wear out as soon, maybe I was right, maybe not.  I was quite happy with the LT's but as Fast Eagle stated, the load carrying capacity is vastly different.  If you find LT's that suit your price range make sure that they are well within the load carrying capability that you want.  For instance if you have D rated tires right now and find E rated LT's then you should be fine.  But if your present ST tires are right up against their load rating then the LT's are not going to be up to the job.

All the noise about Chinese tires being prone to failure isn't something that I pay a lot of attention to.  I'd rather purchase USA made tires mainly because I'd rather promote my own country and its workers.  Sadly that's not such an easy thing to do these days.  Currently we're running Goodyear Marathons (6 wheel positions) and I'm quite impressed with them.  They're ST tires and after running them just over 20k miles they appear to have at least 50% tread wear left on them.

As far as the arguement that ST's are designed to sit still longer and have higher UV protection that vehicle tires, I'm not convinced.  If Fast Eagle would chime back in on this I'd like to hear his opinion.
 

BruceinFL

Well-known member
Joined
Mar 12, 2005
Posts
3,205
Gary RV Roamer said:
ST tires are rated for trailers only. The side walls are stiff, making them unsuitable for use as steer axle tires but good for trailers. The shortcoming is that they are limited to 65 mph and many of them are of mediocre quality. There are a few good ones - Maxxis is one of te better brands.

Goodyear G614 tires are ST (trailer tires) and are rated for 75 mph. They only come in one size (LT235/85R16) and are Load Range G tires.
 

cva61

Well-known member
Joined
Nov 1, 2009
Posts
86
Location
Lenexa, KS
Looked at the Goodyear site and they list the G614 as an LT tire.  Even the designiation listed by BruceinFL says its a LT tire not a ST as indicated in the post.
 

Jammer

Well-known member
Joined
Dec 20, 2009
Posts
1,491
flagstaff said:
I have seen some tire threads that will sometimes refer to using LT tires on a trailer.

What's the difference and pros and cons?

It's a controversial topic.

The best information I have been able to find, based primarily on posts from an engineer who worked for several major tire manufacturers during a career spanning over 40 years, is that there are very few differences between LT and ST tires of the same size and ply rating.  The main physical difference is a slightly shallower tread to provide better cooling when new, and the tread patterns themselves differ slightly.

ST tires carry higher load ratings, and lower speed ratings, than LT tires of the same size.  This is supposed to be because of differences in intended use.  The load ratings haven't been updated since the early 1970s and are for the most part based on a short-distance, occasional-use model that hasn't really applied since the 1950s and maybe didn't even apply back then.  One of the few things that people on RV forums can agree upon regarding tires is that ST tires, run at their maximum load for extended periods, fail.

People trying to switch to LT tires find that they have trouble getting ones that have high enough load ratings, and so in most cases they switch to larger rims and larger tires.  Well, if you switch to larger rims and larger tires, you'll have better luck with your tires whether you use LT or ST tires, just because the tires have more inherent capacity, so the success people have with LT tire conversions doesn't have anything to do with the LT tire.  They could have switched to a larger ST tire and had the same results.

Broadly speaking, LT tires are made in larger quantities and therefore in newer production facilities while ST tires, being a specialty item, tend to be produced in smaller and older production facilities.  I suppose we could speculate that the quality might be a little more uneven with ST tires as a result.

But the thing to watch is that 16" LT tires aren't produced in the quantities they once were, and will become obsolete relatively soon, because new production trucks have all switched to 17" and larger rims.  So the usual 16" rim and LT tire conversion may, in the long term, require a specialty low-volume tire anyway.
 

Opontee

Active member
Joined
May 31, 2012
Posts
38
Location
League City, Texas
lavarock1210 said:
I have had many LT tire failures.  Close to 5 as far as I can remember.  I have never had a ST tire failure. 

Lucky you. I had 2 ST tires on my 48' Haulmark racecar trailer blowout in 1.5 years. Moved to LT and never had a problem. Of course the ST were cheap China tires.
 

Gary RV_Wizard

Site Team
Joined
Feb 2, 2005
Posts
73,974
Location
At our Silver Springs FL home
When I replaced my 15" tires this year, I was not able to find any LT tires made in that size.

You won't find much  choice of sizes and loads in LT tires unless you can use the 16" size.

You will have to choose a fairly high Load Range model to get equivalent carrying capacity to an ST.  Obviously, anytime you buy a tire you need to have the correct load range (carrying capacity) for your axle weights. All bets are off otherwise.

I also found some dealers who said that their company policy would not allow them to put LT tires on a trailer.  That was Sam's and they were adamant.

That's why I mentioned the confusion about "high flotation" vs Light Truck numeric in the LT designation. That's what's behind this issue. They are talking about the high floatation LTs but their policy just says "LT", without distinguishing.  On a high flotation tire, the LT will be at the trailing end rather than the beginning of the size, and the first number will typically be tire diameter (e.g. 33R16) rather than the tread width. Maybe the big companies can't afford the chance that a clerk or tire tech will mistake one for the other.
 

longhaul

Well-known member
Joined
Dec 21, 2008
Posts
542
flagstaff said:
I have seen some tire threads that will sometimes refer to using LT tires on a trailer.

What's the difference and pros and cons?
  Wow. Its a big subject.
In the beginning all we had to use on trailers were  various sizes of 12"/13"/14" passenger and 14"/15"/16" truck tires. The P or passenger tires back then had a 32 psi max which made them suspect to the tires bead breaking loose while going around corners.  Thats where the truck (todays LT) tires came in as they had more carcass plies and higher pressures.  Many folks didn't like the high cost of a truck tire at repacement time as in many cases the tire life expired before the tire wore out.

Enter the ST tire with its lower cost, than the LT tire, but its weight carrying performance was superior to the P tire.  The ST has a 3-5 year life recommendation vs seven for the LT.  Back then all ST tires were made in the USA and yes we had the same issues as we do many years later with the china made ST tires.

The  LT has a tread depth up to 16 or 17/32nd in some cases vs 9 to 11/32" for the ST. The thicker tread allows the tires carcass to sit farther away from the road surface = a cooler running carcass. One thing I found when running equipment trailers 24/7 making a living was a tire close to the tread wear indicators ran much hotter than the tires with the thicker threads. 

The LT235/85-16 E may weigh 46 lbs vs the ST235/80-16" E at 34-36 lbs. That says volumes to the savy trailer owner looking for the best long term reliable tire for a trailer.

The LT235/85-16 E XPS Ribs are recommended for commercial trailer service by Michelin (and weighs 56 lbs). No ST tire has ever had that kind of a recommendation.

Many RV trailers come OEM with LT tires or were a upgrade option.  LTs in a trailer position is nothing new. Just lots of new people to the trailering world.




 

BruceinFL

Well-known member
Joined
Mar 12, 2005
Posts
3,205
cva61 said:
Looked at the Goodyear site and they list the G614 as an LT tire.  Even the designiation listed by BruceinFL says its a LT tire not a ST as indicated in the post.

According to Goodyear, the G614 RST is a trailer tire even though it has a LT designation. This was confirmed by the Goodyear rep at the Daytona GS Rally. Check the website here: http://www.goodyear.com/cfmx/web/truck/line.cfm?prodline=160007
 

donn

Well-known member
Joined
Nov 8, 2009
Posts
4,502
BruceinFL said:
According to Goodyear, the G614 RST is a trailer tire even though it has a LT designation. This was confirmed by the Goodyear rep at the Daytona GS Rally. Check the website here: http://www.goodyear.com/cfmx/web/truck/line.cfm?prodline=160007

Is or can be used?  There is a hugh difference.  LT designation means they can also be used all position on a Light Truck!  Same for Michelin XPS Ribs.  ST tires are a low priced alternative designed for ONLY trailer service.  Lots of people claim stiffer side walls and all sorts of things attributed to ST tires.  Most of which are untrue.  Heat and speed are their biggest killers.  But since most interstate freeways have at least a 65 MPH and in some cases much higher speed limits people tent to drag their trailers at the speed limit as they are in a hurry to get camping.  Those ST tires once they,go over that 65 MPH speed limiter start to over heat.  May not be this trip, but sooner or later they,will be killed, often times with dramatic results.  So if the option is there, ie 16 inch wheels, then in the real world a LT tire with a 99 MPH speed rating is a much better choice.  There are a few people who claim the ST tire is superior or the only thing you can run citing some obscure or non existent regulations.  Sme of those people have if you can get,them to admit it, blown many many ST tires.  Your choice as always to do what you want but there is no way I will ever have a ST tire under any trailer I ever own again.
 

flagstaff

Member
Joined
Mar 7, 2012
Posts
16
Wow,thanks for all the posts.  That was a great primer on the subject.
Current tires are 225/75-15 and am not really interested in going to bigger wheels.

That info about the load carrying capacity was an issue I may not have considered - being one of those sorta newbies.

Again thanks. 
 

COMer

Well-known member
Joined
Aug 25, 2009
Posts
1,663
Sounds like you are going through about the same job I did.  I found no 15" LTs so it made the job easier.  I found STs with a load range E and am quite happy with them.  Plenty of weight capacity and not being able to run 99MPH on the interstates does not limit me that much.  I even have a sister to the Flagstaff (Rockwood) and enjoy it.  Except when tires blow.  But hopefully I am good for awhile now.  Good luck with your decision and your new tires.
 

Gary RV_Wizard

Site Team
Joined
Feb 2, 2005
Posts
73,974
Location
At our Silver Springs FL home
Maxxis makes an ST  225/75R15 and their track record is excellent. At least one of the Maxxis models in that size has an "R" speed rating (106 mph).

Be careful of the speed rating on ST tires - many are rated for only 65 mph. You want a speed index of at least "L" (75 mph) and preferably higher (alphabetically higher letters indicate greater speed). Here is a list of the speed rating codes on the tire sidewall:
http://www.discounttire.com/dtcs/infoSpeedRating.dos
 
Top Bottom