ST vs LT tires

[Phil&Sher]

I read somewhere that ST trailer tires are rated for 65 MPH and LT truck tires are rated for 95 MPH. I also read a post on another forum from a guy who was having lots of tire problems on a heavy fifth-wheel, even though he was cautious about his weight and speed. He switched to from 15" ST's to 16" LT's and his problems disappeared.

[Whirlaway]

Originally Posted by Phil&Sher

I read somewhere that ST trailer tires are rated for 65 MPH and LT truck tires are rated for 95 MPH. I also read a post on another forum from a guy who was having lots of tire problems on a heavy fifth-wheel, even though he was cautious about his weight and speed. He switched to from 15" ST's to 16" LT's and his problems disappeared.

I have to tell you this forum is the greatest thing, next to being on the road and looking in your mirror and seeing your Airstream behind you!!!

I have been reading all the Tire posts the past few days and have decided to go from my factory ST's to the LT's as they seem to stand up better.

What is the advantage of changing from a 15" tire to 16" tire?

Many thanks,

[Phil&Sher]

Well, I'm certainly no tire expert, but I presume that since wheel RPM would be less for a given speed, the tire temps would be lower (sidewalls flexing less). Of course, you'd have to buy 16" wheels and be sure that they'd fit your trailer.

We've only had our (used) trailer for a few months, but the dealer replaced a couple of the Goodyear Marathons prior to delivery due to sidewall bulges on tires that were only a couple of years old.

I keep my towing speed about 60MPH and check the tire pressures daily. No problems so far in about 1k miles, but if any crop up, I'll be switching to 16" LT's.

[Silver Goose]

Originally Posted by Phil&Sher

... you'd have to buy 16" wheels and be sure that they'd fit your trailer...

Don't forget the spare... A less expensive steel wheel with the proper bolt pattern and offset would suffice for spare duty.

[Phil&Sher]

Oops! I forgot about that. Also, my 15" spare fits pretty snugly as it is. I might have to consider the profile of the 16-inch spare if I don't want to carry the spare on the roof

[dznf0g]

Originally Posted by Whirlaway

I have to tell you this forum is the greatest thing, next to being on the road and looking in your mirror and seeing your Airstream behind you!!!

I have been reading all the Tire posts the past few days and have decided to go from my factory ST's to the LT's as they seem to stand up better.

What is the advantage of changing from a 15" tire to 16" tire?

Many thanks,

There are no 15" LTs out there. Gotta go 16".

[dznf0g]

Let me ask this....I've been trying to figure out what to do for a spare. Space in the carrier is a concern, cost is a concern since I don't want to do a 5tire rotation. I have found an inexpensive steel wheel of the proper specs but no inexpensive LT or other high load rated tire at 29.5" diameter.
Then I asked myself, if it's ok to drive to the next tire store on 3 wheels (4th, flat, removed), then why can't you use the stock 15" spare to get to the next tire store? I understand why you wouldn't travel long distances this way, but it is an EMERGENCY spare only for my use.

[UAPachyderm]

I changed to Michelin LT 16" ... best upgrade decision ever! Spare fits fine. Search threads there is a lot of information on this subject here, especially during 2010-2011.

[moosetags]

Generally speaking, ST tires are junk. In Lucy's first 54,000 miles, we went through three sets of these garbage tires. Lucy's original tires were the Goodyear Marathons. These provided us with three catastrophic failures in the first 12,000 miles. We then went to the Maxxis E's. The first set went 28,000 miles before tread separation took them out. We went with another set Maxxis. These only went 14,000 miles before tread separation got them.

I finally wised up and got Lucy a set of Michelin LT's on 16" wheels. Lucy has now gone almost 30,000 miles on these without incident. So far, so good.

Brian

[RTurnConn]

Originally Posted by dznf0g

There are no 15" LTs out there. Gotta go 16".

I just bought four Michelin LT 15 inch tires yesterday. LTX M/S2 235 75 15 108T. There are a number of 15 inch LT tires available.

[Olie]

Originally Posted by moosetags

Generally speaking, ST tires are junk. In Lucy's first 54,000 miles, we went through three sets of these garbage tires. Lucy's original tires were the Goodyear Marathons. These provided us with three catastrophic failures in the first 12,000 miles. We then went to the Maxxis E's. The first set went 28,000 miles before tread separation took them out. We went with another set Maxxis. These only went 14,000 miles before tread separation got them.

I finally wised up and got Lucy a set of Michelin LT's on 16" wheels. Lucy has now gone almost 30,000 miles on these without incident. So far, so good.

Brian

Moosetags,
Nice looking wheels, hub cover and all. Are they Al. or steel? Who makes them?

[dznf0g]

Originally Posted by RTurnConn

I just bought four Michelin LT 15 inch tires yesterday. LTX M/S2 235 75 15 108T. There are a number of 15 inch LT tires available.

Those aren't really true LT tires. They are extra load tires in the range of load range D's. They are rated for 2183 pounds and are not enough for 30'er and IMHO a 28'er. They are probably the best choice for smaller ASes.
Perhaps I should've been more clear and said there are no LRE LT tires in 15".
I have close to 8000 lbs on the axles, hitched and ready to go. 2183 pounds max just isn't enough.

[dznf0g]

This is the explanation. About 2/3 of the way down is the explanation of XL p metrics vs LTs. Also tells of reduced load maximums if used on trucks vs. Cars. How does that relate to trailers.......we'll never know, since neither XLs nor LTs are intended for trailers. What's the difference? Don't know, they both have 3 steel belts. I believe the carcass and sidewalls are much more robust in LTs vs XLs.

Tire Specs Explained: Maximum Load

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Maximum Load

A tire's maximum load is the most weight the tire is designed to carry. Since a tire's load carrying capacity is related to the tire's size and how much inflation pressure is actually used, maximum loads are rated with the tire inflated to an industry assigned inflation pressure.

Additionally, load ranges are used to separate tires that share the same physical size, but differ in strength due to their internal construction. "Higher" load ranges are used to identify tires that have a stronger internal construction, and therefore can hold more air pressure and carry more weight.

Each load range has a assigned air pressure identified in pounds per square inch (psi) at which the tire's maximum load is rated. Listed below are the air pressures at which maximum load is rated for popular P-metric and LT tires:

P-Metric Passenger Vehicle Tires
Load Ranges Abbreviated Max Load Pressure
Light Load (LL) 35 psi (240 kPa)*
Standard Load (SL) 35 psi (240 kPa)*
Extra Load (XL) 41 psi (280 kPa)*
*In an effort to internationally harmonize load ratings and ranges, recently introduced and future LL, SL and XL P-Metric sizes will use ISO/Euro-metric maximum load pressures of 36 or 42 psi
Euro-Metric Passenger Vehicle Tires
Load Ranges Abbreviated Max Load Pressure
Standard Load (SL) 36 psi (250 kPa)
Extra Load** (RF) or (XL) 42 psi (290 kPa)
**Reinforced and Extra Load nomenclature may be used interchangeably to designate heavy-duty tires
LT-Metric and Flotation Light Truck Tires
Load Range Abbreviated Max Load Pressure
Load Range B (LRB) 35 psi (240 kPa)***
Load Range C (LRC) 50 psi (350 kPa)***
Load Range D (LRD) 65 psi (450 kPa)***
Load Range E (LRE) 80 psi (550 kPa)***
Load Range F (LRF) 95 psi (650 kPa)***
***Industry standards specify selected large LT tire sizes be designed with reduced maximum load pressures
P-metric tires used on passenger cars and station wagons are rated to carry 100% of the load indicated on the tire's sidewall (or listed for the tire in industry load/inflation charts). However, if the same P-metric tires are used on light trucks, (pickup trucks and sport utility vehicles for example), their carrying capacity is reduced to 91% of the load indicated on the tire's sidewall. This reduction in load results in causing light truck vehicle manufacturers to select proportionately larger P-metric sized tires for their vehicles to help offset the forces and loads resulting from a light truck's higher center of gravity and increased possibility of being occasionally "overloaded."

For example, P235/75R15 P-metric sized, standard load tires used on cars and light trucks would be rated to carry the following maximum loads at 35 psi:

Cars Full Value 2028 lbs.
Light Trucks 9% Reduced Value 1845 lbs.

Additionally, while a tire's maximum load is the most weight the tire is designed to carry, its load carrying capacity at lower inflation pressures is proportional to how much inflation pressure is used. For example, P235/75R15 P-metric sized, standard load (SL) and extra load (XL) tires used on cars would be rated to carry the following loads at the inflation pressures indicated:

Air Pressure (psi) 20 23 26 29 32 35 38 41
P235/75R15 SL 1543 1635 1753 1852 1940 2028
P235/75R15 XL 1543 1635 1753 1852 1940 2028 2105 2183

Note: 35 psi is the assigned "maximum load" pressure for standard load tires and 41 psi is the assigned "maximum load" pressure for extra load tires.

The above chart correctly shows that an extra load tire is not rated to carry any more load than a standard load tire when both are inflated to the same pressure (up to the standard load tire's "maximum load" pressure of 35 psi). This is because a tire's load capacity is a function of its size (which determines the size of the "air chamber"), its construction (which determines how much pressure can be held) and the actual air pressure used (which determines how many air molecules are forced inside the chamber). All tires with equivalent physical dimensions carry equivalent loads (until they reach their maximum load pressure).

The tire's maximum load is indicated in relatively small sized print branded near the tire's bead (adjacent to the wheel) indicating the appropriate value. Because tires are global products, their maximum load capacity is branded on the tire in kilograms (kg) and pounds (lb). These values can also be found in the industry's tire load & inflation charts.

NOTE: P-metric and Euro-metric sized tires' "maximum load" inflation pressure may be, and often are, different that the tire's "maximum inflation pressure."

[RTurnConn]

Originally Posted by dznf0g

Those aren't really true LT tires. They are extra load tires in the range of load range D's. They are rated for 2183 pounds and are not enough for 30'er and IMHO a 28'er. They are probably the best choice for smaller ASes.
Perhaps I should've been more clear and said there are no LRE LT tires in 15".
I have close to 8000 lbs on the axles, hitched and ready to go. 2183 pounds max just isn't enough.

I feel comfortable with the pseudo LT tires. Yes they are XL. My 31 has a dry wt of 5500 & I will never get close to 8000lbs. I leave a lot of my house at home. If I thought I had 8000 lbs I might agree with you.

[dznf0g]

Originally Posted by RTurnConn

I feel comfortable with the pseudo LT tires. Yes they are XL. My 31 has a dry wt of 5500 & I will never get close to 8000lbs. I leave a lot of my house at home. If I thought I had 8000 lbs I might agree with you.

Yeah, I'm on my IPad and the app doesn't let me see what AS you have unless it is in your text, so I don't know if we're talking Bambis or 34s. I assume you have an older 31. I still bet you'd be surprised if you ran over the scales. Dry weight may not mean much. You're probably still fine with your p metric XLs. Some would still argue that a p- metric doesn't have the sidewalls to stand up to trailer use (they might say the same thing about LTs), but on my old 5500 lb SOB, I used some P225 75 r15 takeoffs and they were fine for 4 years and probably 10,000 miles.

[Phil&Sher]

Originally Posted by UAPachyderm

I changed to Michelin LT 16" ... best upgrade decision ever! Spare fits fine. Search threads there is a lot of information on this subject here, especially during 2010-2011.

Thanks.......Great to know.

[handn]

Originally Posted by RTurnConn

I just bought four Michelin LT 15 inch tires yesterday. LTX M/S2 235 75 15 108T. There are a number of 15 inch LT tires available.

Me too, I didn't want to pop for 4 new 16 wheels. My tires each carry about 2100 pounds, plenty of capacity for my 6300 gvw Safari. There is lots of room in the wheel wells of my 2004 Safari for the slightly bigger tires.
These tires ride much smoother than my E rated ST 225's (I had to switch to E's because I had serial tire failures with D rated 225 GYM's). I can run 70 mph all day in 100 degree plus temps and not have a problem.
There about 4 or 5 threads with hundreds of posts on this forum about upgrading to "P" and "LT" tires. No reason not to other than a slight increase in cost per tire and tight wheel well clearance in some model AS's. Some heavy, double axle Airstreams may have to go with 16 inch wheels to get a D or E loan range LT tire. In the 235 15 inch size, any load range higher than C is hard to come by.

[RTurnConn]

I am a newbie to AS but if we all listened to, and believed every comment posted we would have an AS with no tires or batteries or convertors for that matter. You just take it all in, use your own intellect, and make what you believe is the best decision. The input fom others is invaluable however.
My AS is a 1985 31 ft. limited. My owners manual lists the dry wt as 5500 lbs. I think as the years went on the general weight increased.

[Gene]

We changed to 16" Michelin LTX tires a couple of years ago and are very happy with them. We now have something like 24,000 miles on them and they are wearing much better than the Marathons did. I have been running 68 lbs. in them, but have increased it to 72 as the edges were wearing slightly faster than the centers. The Marathons lost air despite changing valve stems. The Michelins do not lose air.

We got the same wheels Moosetags did. They come from Tredit, a tire and wheel company in Indiana that Airstream gets supplies from. They are not the only company that has similar wheels. Just make sure they are rated for Load Range E tires and have 0˚ offset.

It is difficult to find a good LT tire in 15" for the size tire Airstream has been using in recent years, so we went to 16" wheels after measuring the space available about 100 times. We wanted Michelins because we have always had good experiences with them and they ride smoother than many other tires.

We got 5 new wheels, all the same, and rotate the spare around and will thus get more miles out of the set of 5 wheels and tires. The tire carrier has steel holders around it that can be bent outward to fit the 16" tire, but we carry it in the truck bed as it is easier to get in and out and easier to check air pressure.

Some people use the Michelin Rib tire. This is a tire designed for commercial trucks and the carcass will last a very long time as the tire is meant to be retreaded. It has steel cord in the sidewalls and appears to be a very firm tire, perhaps too much so. I expect the carcass will last well over 100,000 miles and seems like overkill to me. The firmness of the sidewalls may make it harder to back up at extreme angles because of the inability of the tire to bend sideways until it skips. The LTX looked like the best deal—it should last 50,000 miles or more and we will probably get to that in 5 years of use when it is time to get new tires anyway.

ST tires are not speed rated. It is suggested not to go more than 65 mph with them, and if you go faster to increase air pressure. Most speed rating is done because of gov't regs on passenger cars. I don't believe LT tires have to be speed rated, but many are and the ratings are in the 90's or higher. It's rough not to be able to tow at 120 mph, but you have to accept certain limits to have an Airstream.

Gene

[r carl]

Originally Posted by dznf0g

There are no 15" LTs out there. Gotta go 16".

I put these 15" LT tires on my trailer and my worries about tires disappeared.

Yokohama RY215