Need tire education

[Hideout17]

I am new to TT tires. Where do i find speed ratings on them?. I have no plans to go 70 or 80 mph but would like to know. If i looked at my tire pressure decal right my pressure says 50 psi. My dry wieght is 6200. I will get brand and tire size and post it here tomorrow.

[bsmith0404]

In the sidewall there will be a letter typically J, K, or L for trailer tires, 62, 68, 75 mph respectively. It is usually after the load range numbers such as 112/114K load range D. The example I gave is not accurate/actual numbers from a tire. The 112/114 are load indexes of weight for dual and single wheel application, the K would be speed rating of 68 mph and D is the load range.

[cathcartww]

ST tires are manufactured to a different standard than most other tires. The only way to see what the speed rating is to go to the manufacturers website or literature. The default speed at which ST tires are rated is 65 mph, but some manufactures claim their tires can be run at higher speeds - in some cases if air pressure is increased, and in other cases if the load range is downgraded.

If you are lucky enough to have 16" wheels, there are some LT tires that are rated by their manufacturer for "all position" or trailer service, and those tires will most likely be labeled with the rating system described above.

The best general advice I have seen is to buy the highest load range tire you can get in a size that fits your wheel, then inflate it to the maximum pressure that the wheel is rated for - and have the tires balanced when they are installed.

[bsmith0404]

From the Carlisle website. Additionally, the Rainier tires that Jayco uses are also labeled with an L speed rating with 75 mph right next to it. It appears many, if not all, ST tire manufacturers are now using speed ratings, unlike in the past when all ST tires were just 62 or 65.

How fast can I travel on Carlisle trailer tires?

In the past, most trailer tires were rated at 62 or 65 mph. Today, some of our tires are "rated" (speed symbols) at 87 mph (N), some at 75 mph (L), some at 65 mph (J: ST tires) and some at 62 mph (J: non-metric tires).

Please remember that speed ratings are test speeds and not recommended driving speeds. The ratings apply only to the tire itself, and not a particular vehicle. The speed rating does not mean that the vehicle can be safely operated at the tire's rated speed.

We recommend driving no more than 60 mph when towing a trailer. Please always drive at a safe speed and abide by the posted speed limit.

[Hideout17]

Thank you all for the info. I have no intention of going 75 plus just looking to see what I have.

[cathcartww]

That is great information. Maybe some of the manufacturers are admitting the ST standard is inadequate, and offering a more robust product to the marketplace!

[bsmith0404]

That is great information. Maybe some of the manufacturers are admitting the ST standard is inadequate, and offering a more robust product to the marketplace!

Personal opinion, it's a marketing scheme. To many people are ignoring safe towing speeds and speed ratings with the increased speed limits on the highways. They are experiencing blow outs and blaming the more craftsmanship of the tires. They are then buying LT tires instead of ST. If an ST manufacturer wants to stay competitive they need to produce a tire that will bridge that gap. Any company that puts their tires through actual testing in order to obtain the standard alpha speed ratings higher than the standard 65 is going to appeal to many consumers thinking they are now safe to tow at 75. Of course, if they're good for 75 then they can most likely handle 80 right?

On a more positive note, it could also be an attempt to create a safer tire knowing that many people are going to ignore the 65 mph rating when the speed limit is 75 or 80.

[cathcartww]

My personal opinion is that the industry standard “ST” tire standard is inadequate for the service the ST tires are exposed to. My opinion is based only on my own personal experience, and anecdotal experience of others.
Back in the late 1970’s through the early 1980’s, I was a boat dealer, and we towed all kinds of boats – from 19 footers weighing 2500 lb on a single axle trailer, up to 15,000 lb 30 footers on triple axle trailers - up and down I95 between New Jersey and Florida. We always used the bias ply trailer tires that were available at the time. We would carry plenty of spares, but seldom, if ever, had a problem that could not be traced to a road hazard or axle-bearing-wheel-suspension problem.
Back in the day of cotton tire cords, tires were rated by how many plies they had – the more plies, the stronger the tire, and higher load range. If I remember correctly, 2 ply was A, 4 ply was B, 6 ply was C etc. When nylon and polyester came along to replace cotton, it was twice as strong, so a fewer number of plies was needed to make a tire of the same strength. We saw labels such as 2 ply/4 ply rating, 4 ply/8 ply rating, etc.
Still later, Michelin figured out how to make radial ply tires using steel belts, and that really changed things, but the industry stuck to the “ply rated” terminology even though bias plies were no longer used.
Somewhere during this, the overall quality of trailer tires seemed to deteriorate – I personally do not think a modern day load range “D” ST radial tire holds up anywhere as well as the 4 ply/8 ply rated bias trailer tires we used 40 years ago.
On the other hand, we do seem to ask more of our ST trailer tires as we do our car and truck tires. For instance, here are my three personal vehicles, using the maximum axle rating for each – I know none of them are really running at the maximum most of the time, but I bet the Ford and trailer are close when we are towing:
1995 Chevy G20 Van, front 3400lb, rear 3406lb, running 31x10.5R15LT LR C Tires rated 2270lb @ 50psi – they are loaded at about 75% capacity.
2002 VW Beetle, front 2183lb, rear 1588lb, running 205/55R16 91H tires rated 1356lb @ 44psi – they are loaded to about 80% capacity.
Ford E350 Van, front 4600lb, rear 5360lb, running LT285/75R16 LR E tires rated at 3750lbs @ 80psi – they are loaded to about 71% capacity.
2015 Outback 277RL, 4400 lb axles, came with ST225/75R15 LR D tires Chinese tires rated at 2540lbs @ 65psi – they were loaded to 86% capacity
We blew on of the LR D tires last winter – no obvious hazard, and pressures were OK 150 miles earlier – go figure. We replace them with Maaxis LR E rated at 2830lb @ 80psi, so they are loaded at about 77%, which is more in line with the other vehicles.
Hoping for the best, but sure wish there were more commercial trailer tires available in 15” !!

[Hideout17]

The tires on my TT are karrier towmaster 205 70r14.....anythi2to worry about or are these a ticking time bomb.

[bsmith0404]

Towmaster has had a history similar to the tow max that many people complain about. They COULD be a ticking time bomb, but could also last thousands of miles.

My advice, if you're asking the question you are already concerned. You don't need the stress of worrying about your tires every time you set out on a trip. If it were me, I'd spend the $400 for peace of mind. Just because you replace the tires obviously doesn't mean you will never have a problem, but your chances are less likely with a good, reputable brand and you will worry less.

For me, I have a slide out with hydraulic lines above each set of tires, the amount of damage that can occur with a blowout is extensive.

[notanlines]

Hideout, what Brent said is on the money. Our blowout on our Raptor last fall cost Geico $8800 and Brenda and I a world of grief. Even took out one of our fuel tanks and the fuel pump. Watch your tire pressures very, very closely. I probably don't need to tell you to pay the same attention to your TV also. There is a world of info on this site about tires. Your job is to glean what info can be had and act accordingly. By the way, are you headed to Florida for the winter or just for a little trip? Pa winters suck right out loud......:D

[CWtheMan]

The tires on my TT are karrier towmaster 205 70r14.....anythi2to worry about or are these a ticking time bomb.

Is the real size designation ST205/75R14C (LRC)?

[Hideout17]

Hideout, what Brent said is on the money. Our blowout on our Raptor last fall cost Geico $8800 and Brenda and I a world of grief. Even took out one of our fuel tanks and the fuel pump. Watch your tire pressures very, very closely. I probably don't need to tell you to pay the same attention to your TV also. There is a world of info on this site about tires. Your job is to glean what info can be had and act accordingly. By the way, are you headed to Florida for the winter or just for a little trip? Pa winters suck right out loud......:D

Going to florida for november, then to savanna for decemeber.

[Hideout17]

Is the real size designation ST205/75R14C (LRC)?

Im typing this as i am looking at them. ST 205 75 R14. Dot number 7YT8. Karrier loadstar

[CWtheMan]

Im typing this as i am looking at them. ST 205 75 R14. Dot number 7YT8. Kinda Karrier loadstar

Somewhere on that tire there has to be a load range letter. Probably like this LRC or printed out Load Range C.

[Hideout17]

Somewhere on that tire there has to be a load range letter. Probably like this LRC or printed out Load Range C.

Load range c

[CWtheMan]

Load range c

ST tires that do not have a speed restriction letter somewhere on their sidewall default to 65 MPH unless in place of a speed letter there is a printed speed restriction in MPH.

Regardless of what Carlisle says the only speed restriction for the letter J is 62 MPH.

All new ST imports must have speed letters on them or pay steeply increased tariffs. So it's happening. The TRA has approved the ST tires up to 81 MPH. Some (Carlisle again) are using letter N=87 MPH.

[Hideout17]

Well i have no plans of going 85mph. 60 to 65 is just fine. When traveling on my harley my thought was ill get there when i get there. I want to enjoy myself and actually get there in one piece. So with my TT it will be the same...

[CWtheMan]

When a tire manufacturer puts a speed restriction on their tires they are saying that the tires will carry their full load capacity up to and including that speed restriction.

In the past, Keystone RV trailers have been equipped with tires that equal the trailer’s established GAWR. In other words, 2540# tires on GAWR 5080# axles or 3000# tires on 6000# GAWR axles. When an owner of one of those trailers puts enough cargo into the trailer to equal its maximum cargo capacity the tires are going to be stressed and will degrade. Once they degrade a few percentage points they are severely overloaded at their maximum speed restriction.

As the tires degrade the overloaded condition causes excessive heat to the carcass. As it heats, the adhesion between carcass and tread is lost and tread separation is going to happen.

Highly stressed tires need to be changed earlier than lower stressed tires. Its hard to talk someone into changing tires that look “like new” so we see the results on the highways where the separated treads are left for someone else to pick-up and dispose of.

[Dodgeman]

Question here is it OK to put car tires on a trailer? My trips are usually 300 miles and a couple 500 miles thats one way. I usually travel at normal highway speeds 70 to 80 mph. Trailer is not overloaded. 238ml passport.

[cathcartww]

Question here is it OK to put car tires on a trailer? My trips are usually 300 miles and a couple 500 miles thats one way. I usually travel at normal highway speeds 70 to 80 mph. Trailer is not overloaded. 238ml passport.

Generally speaking, no. ST tires are not designed to be towed at high speeds - and in my opinion, depending on your tow vehicle to trailer weight ratio - anything over 70 mph is nuts.

The only non-ST tire I know of is the Kuhmo 857, which is a euro-sized tire rated for trailer use. It also has much higher speed ratings ...

[bsmith0404]

Question here is it OK to put car tires on a trailer? My trips are usually 300 miles and a couple 500 miles thats one way. I usually travel at normal highway speeds 70 to 80 mph. Trailer is not overloaded. 238ml passport.

Car tires, NO. They re not made to handle the weight. Now if you are thinking LT tires, that's another issue that has been debated many, many times on this forum. You can go to the tires, tires, tires section of the forum or use the search function for more information.

[CWtheMan]

Question here is it OK to put car tires on a trailer? My trips are usually 300 miles and a couple 500 miles thats one way. I usually travel at normal highway speeds 70 to 80 mph. Trailer is not overloaded. 238ml passport.

Passenger tires are more commonly used on large dual axle bass boat trailers. They are not recommended for the taller RV trailers because of the sway forces. However, they do provide a softer ride for the trailer and are often reported as being used by Airstream owners in their forum.

In your case you would have to step up to a 15” tire such as the Michelin Defender P235/75R15 109T XL. For trailer service it would have to be derated to 2064# of load capacity at 50 psi. It’s about 1 & ½” wider and more than 2 & ½” taller then the OE tires. Your wheel wells and axle spacing would have to accommodate those larger dimensions.

IMO the Kumho tires previously mentioned are the best option.

[Dodgeman]

Thanks for the info.

[mfifield01]

I was curious about the stock tires on my Passport and looked at the speed rating. I assumed it was 65. On my boat trailer it was 65. What I noticed is that the Trailer King ST Radial speed is L, which is actually 75 MPH. I have been keeping the speed at 65 or below, it's good to know these are rated higher.

[JRTJH]

I was curious about the stock tires on my Passport and looked at the speed rating. I assumed it was 65. On my boat trailer it was 65. What I noticed is that the Trailer King ST Radial speed is L, which is actually 75 MPH. I have been keeping the speed at 65 or below, it's good to know these are rated higher.

We have a "resident expert" on tires that's a member of the forum, I'm sure he will "tune in" before long and give you some information. In the mean time, it's my understanding that the ST tire regulations are undergoing some changes in not only tire specifications but also in how they are regulated. A part of that is upgrading (for lack of a better term) the speed rating on ST tires. You're correct, in the past, the speed rating for most ST tires has been 62 or 65 MPH. In the future, many ST tire manufacturers are listing their tires at a 75 MPH rating, but not all manufacturers are "upping the speed rating", so your tires may or may not be upgraded.

Something that "confuses the current situation" is a comment on many ST tire manufacturer's websites that has "disappeared in the past year". That comment said something to the effect of this: "ST tires may be operated above 65MPH (maximum 75MPH) by increasing the cold inflation pressure by 10PSI." The comment went on to state not to exceed the maximum wheel pressure and the increased pressure did not increase the tire load rating. This, if one tends to "overanalyze" things, can be "twisted" to maybe interpret that "IF" tires back then could be operated at 75MPH with increased pressure, can current tires also be increased? and does that mean that current tires and older tires are actually the same tires with different speed rating or ???

Now, a question I have not seen any answers for is: Does this increased speed rating include any "change in the physical tire" or is this just a change in paperwork???? I can't tell you, but I do feel very confident in saying that the increased speed rating won't affect any tires that have already been produced, so unless you buy new tires that are marked with a speed rating of L or buy new tires that somehow are "designated for 75MPH" during the next few years, I'd be very suspicious of any ST tires that aren't physically marked with a speed rating. My "best guess" would be that they are rated at either 62 or 65 MPH unless specifically stamped with a higher speed rating.

CWtheman, what say you ????

[CWtheMan]

I have recently visited a large RV showing here in SC. All of the Keystone RV trailers (large & small) were fitted with new Trailer King tires serviced with 100% nitrogen. All of them were also marked with a speed letter "L" for 75 MPH.

Without an official modification in the ST tires testing I will have to assume the higher speed rated ST tires have been beefed up in some way so their maximum load capacity can be carried at higher speeds. It's very hard to get such information from tire manufacturers if they don't publish it. However, I have read that the TRA now approves ST tire manufacturers to go as high as 81 MPH with their speed ratings. The TRAs previous approval for all ST tires was 65 MPH unless otherwise marked.

I've only seen a single official publication from any ST tire manufacturer that approves their ST tires to be inflated 10 PSI beyond the PSI rating on the tire's sidewall, to increase the speed by 10 MPH. That's Goodyear, for their Marathon brand ST tires. Evidently GY has determined by making the tire stiffer with the additional 10 PSI it allows it to carry its maximum load capacity 10 MPH faster. I would not recommend that procedure to be used with other brands unless approved by their manufacturer.

I don't know where Goodyear stands legally with the TRA and FMVSS on that subject. But, personally, I don't think they would publish such a procedure without their approval.

On the subject of Passenger tires on RV trailers. FMVSS 571.110 clearly gives approval for their use up to 10,000# GVWR. However, they must be degraded by about 10%. It's done by dividing the tires load capacity by 1.1.

[mfifield01]

Do you know why the tires have two load ranges? Are they de-rated at the L speed designation. My tires show 100/96L.

[buzzcop63]

Reference Trailer Life, February edition, on page 8 in a discussion of tire failures. Having read and commented on tire problems on this Forum I would like to add one of the people commenting in Trailer Life. "Tires tended to fail when ever he was carrying more then about 70% of the recommended load rating for the trailer." "Since adhering to the 70 percent rule, we have had no more trailer tire incidents" The writer states that they have logged hundreds of thousands of trailer miles for vacation travel and with racecars. Myself I run Tire Minder, 55MPH is my speed limit and at each 1-hour of driving stop and check by feel each tire and axel to see if all match temperatures as well as look over the tire for any damage.

[bsmith0404]

Do you know why the tires have two load ranges? Are they de-rated at the L speed designation. My tires show 100/96L.

That is single/dual wheel configuration ratings.

[CWtheMan]

Do you know why the tires have two load ranges? Are they de-rated at the L speed designation. My tires show 100/96L.

The 100/96L is what is know as a tire's service description. The 100 is the load index for fitment as a single on the end of an axle. The 96 is the load index when two tires (dual) are on the end of each axle. The letter L is a speed symbol for the tires speed restriction (75 MPH).

Service descriptions are not the official indicator for a tires load capacity on ST or LT tires. For them it's the load range letter. However, tire manufacturers are allowed to put both methods on a tires sidewall. It is becoming more and more common to find service descriptions on ST tires. Especially now when all foreign ST and some LT tires must have a speed restriction on the sidewall to qualify for reduced tariff fees.

Any ST tires not marked with a speed letter are 65 MPH tires. Currently there is no speed letter for 65 MPH.

[cw3jason]

Just my 2 cents. 65mph is fast enough when hauling over 14,000lbs of trailer. I still need to be able to respond in an emergency. I could have 80mph tires and still only drive 65.

Sent from my SM-G900V using Tapatalk

[CWtheMan]

IMO the most important thing about speed codes for RV trailer tires is weight. On all tires the speed letter is telling us that the tire can travel at that speed and carry its maximum load capacity. Once over the limited speed the tire starts to degrade. As the speed goes above the tires limit it degrades faster. Pretty soon tread separation starts.

Lets say your tires are rated at 65 MPH and you’re in a hilly area. The tendency is to increase speed down hill to build momentum to climb the next one. Every time you exceed 65 MPH going down hill its possible you’re tires are degrading.


NOTE: The polyester cording found in most ST tires starts to melt at about 200 degrees C.

[Desert185]

IMO the most important thing about speed codes for RV trailer tires is weight. On all tires the speed letter is telling us that the tire can travel at that speed and carry its maximum load capacity. Once over the limited speed the tire starts to degrade. As the speed goes above the tires limit it degrades faster. Pretty soon tread separation starts.

Lets say your tires are rated at 65 MPH and you’re in a hilly area. The tendency is to increase speed down hill to build momentum to climb the next one. Every time you exceed 65 MPH going down hill its possible you’re tires are degrading.


NOTE: The polyester cording found in most ST tires starts to melt at about 200 degrees C.

That's 392F. A pretty good margin, I'd say.