235/75R15XL vs 225/75-15 trailer tire

[Xenomorph]

Originally Posted by Kosm1o

Ultimately, you have to feel comfortable and safe with your choice. I would read Andrew T's post on this thread again or send him a PM. The load rating on that tire is 2185 not 1985. Besides that, what is a margin of safety on a ST tire at any load rating? The failures reported on this forum and many other RV forums were most likely not from overload. Read them yourself. I chos e the Michelins because I would feel more comfortable with them even if I was closer to the max rating.
Kos

I think the sidewall says 1985lbs at 50 psi and then also rates it at a 108 which comes to 2200lbs. Not sure which one is more correct. I will take a pic of mine tomorrow and post it to make sure.

[perryg114]

There is no margin of safety on ST trailer tires. They take a crappy made tire and overrate and over pressure the tire. That is probably one reason that they explode with such force.

Perry

Originally Posted by Kosm1o

Ultimately, you have to feel comfortable and safe with your choice. I would read Andrew T's post on this thread again or send him a PM. The load rating on that tire is 2185 not 1985. Besides that, what is a margin of safety on a ST tire at any load rating? The failures reported on this forum and many other RV forums were most likely not from overload. Read them yourself. I chos e the Michelins because I would feel more comfortable with them even if I was closer to the max rating.
Kos

[r carl]

Originally Posted by perryg114

There is no margin of safety on ST trailer tires. They take a crappy made tire and overrate and over pressure the tire. That is probably one reason that they explode with such force.

Perry

And if you want the loudest explosion get a china E rated tire.

[Scott J-24]

Originally Posted by r carl

And if you want the loudest explosion get a china E rated tire.

can you say BOOM

[Whirlaway]

Happy Thanksgiving to ALL!

First off thank you for starting this thread since I need new tires on my
AS 27. I have some beginnings of dry rot on one side wall.

However after reading all these posts with great interest, I just went outside and looked at the factory ST tires. The first set of numbers:
ST 225.

I have been clicking on all the links and no where does it explain how
a ST 225; can become a LT 235? Does this number designate model or a of tire size?

Could someone kindly explain the difference between these two major points through out this post. I would like to pick the most correct tire for my AS 27. After reading the posts I am very confused trying to pick up on the "little" differences.

1. ST 225 vs. LT 235 does this designate a size or model?
2. LT 235/75R 15 vs. LT235/75R15 XL

Many thanks,
Lin.

[RLS]

Originally Posted by Whirlaway

Happy Thanksgiving to ALL!

First off thank you for starting this thread since I need new tires on my
AS 27. I have some beginnings of dry rot on one side wall.

However after reading all these posts with great interest, I just went outside and looked at the factory ST tires. The first set of numbers:
ST 225.

I have been clicking on all the links and no where does it explain how
a ST 225; can become a LT 235? Does this number designate model or a of tire size?

1. ST 225 vs. LT 235 does this designate a size or model?
2. LT 235/75R 15 vs. LT235/75R15 XL

Many thanks,
Lin.

ST stands for trailer tire (speed rating of 65 MPH), LT means light truck. 225 is the width to height ratio of the tire. A 225 is narrower than the 235. XL means extra load capacity of the tire. JMHO

[Whirlaway]

Originally Posted by RLS

ST stands for trailer tire (speed rating of 65 MPH), LT means light truck. 225 is the width to height ratio of the tire. A 225 is narrower than the 235. XL means extra load capacity of the tire. JMHO

Thanks!

[azflycaster]

I believe that 225 (or 235) is the width of the tire in millimeters and 75 is the aspect ratio or the percent of the width that equals the sidewall height.

[RLS]

Originally Posted by azflycaster

I believe that 225 (or 235) is the width of the tire in millimeters and 75 is the aspect ratio or the percent of the width that equals the sidewall height.

That does make more sense. Thanks for the input

[Xenomorph]

Originally Posted by Whirlaway

Happy Thanksgiving to ALL!

First off thank you for starting this thread since I need new tires on my
AS 27. I have some beginnings of dry rot on one side wall.

However after reading all these posts with great interest, I just went outside and looked at the factory ST tires. The first set of numbers:
ST 225.

I have been clicking on all the links and no where does it explain how
a ST 225; can become a LT 235? Does this number designate model or a of tire size?

Could someone kindly explain the difference between these two major points through out this post. I would like to pick the most correct tire for my AS 27. After reading the posts I am very confused trying to pick up on the "little" differences.

1. ST 225 vs. LT 235 does this designate a size or model?
2. LT 235/75R 15 vs. LT235/75R15 XL

Many thanks,
Lin.

Unfortunately there aren't a lot of options in the 225 size. 235 is 10mm or .4 inches wider on the tread size. Good luck!

[Xenomorph]

I checked my sidewalls on my Michelin P235/75R15 M/S 2 and they are rated 2183lbs at 50 psi like Kosm1o mentioned. Michelin website incorrectly says 1985lbs.

[perryg114]

My BF Goodrich tires say the same thing. 2185 lb but the specs say 1985lb. As mentioned above P metric tires used on light truck have to me derated by 9%. If you do the math that is where the 1985lb number comes from. Trailer tires have an easy life sorta like the back tires on a front wheel drive car.

Perry

[Kamiak]

The 225 or 235 refers to the width of the tire in millimeters at its widest point, i.e., sidewall to sidewall, not across the tread. The larger number will likely produce a wider tread, but not necessarily 10mm. In any case, all else remaining the same, a 235 relative to a 225 also results in a slightly larger sidewall dimension. In this case, the sidewall height increases 75%*10mm=7.5mm, or about .3 inches. Thus, the overall height of the tire increases approximately .6 inches, and the width increases about .4 inches between the 225 and the 235 (assuming the same aspect ratio). Which means from the 225 to the 235, the additional encroachment into the wheel well is about .3 inches vertically, and about .4 inches horizontally.

[Xenomorph]

Originally Posted by Kamiak

The 225 or 235 refers to the width of the tire in millimeters at its widest point, i.e., sidewall to sidewall, not across the tread. The larger number will likely produce a wider tread, but not necessarily 10mm. In any case, all else remaining the same, a 235 relative to a 225 also results in a slightly larger sidewall dimension. In this case, the sidewall height increases 75%*10mm=7.5mm, or about .3 inches. Thus, the overall height of the tire increases approximately .6 inches, and the width increases about .4 inches between the 225 and the 235 (assuming the same aspect ratio). Which means from the 225 to the 235, the additional encroachment into the wheel well is about .3 inches vertically, and about .4 inches horizontally.

Thanks for the breakdown

[RTurnConn]

Originally Posted by Andrew T

Hi Everyone

It appears that what Michelin has done is rationalize two tires into one. Which makes sence considering how few 15" tires there are getting to be. Previously the P235/75R x 15XL tire carried 41 PSI. The LT 235 carried 50 PSI.

Now that the LT 235's are no longer available the 235 XL tire carries 50 PSI. I think this is the same tire as the old LT tire. The sidewalls feel the same, the old XL was softer.

We have a set of the new XL's running on a commercial unit that weighs 7800 lbs. on the axles. These tires have about 8000 miles on them now at high speeds with no problems. They appear to run the same temperature as the LT's.

I feel considerably more confident with the 50 PSI Michelin 235 XL's on an Airstream than any trailer tire, espessially heavier tandams such as 30 classics etc. One big benefit of these is that they stay in balance where as the TT tires tend to loose theirs after a while. Beyond that they do have considerably more traction in a panic stop, espessially if it happens to be wet.

I hope this helps.

Andy

Andy, you convinced me. Bought 4 LTX M/S2 tires today.load rating on the tire is 2183#(so we can start that debate again). Got them at a local independent for $630 out the door(mounting & balancing, tax etc.) Michelin now has a $70 "rebate" that took the price down to $140 per tire installed. Worked for me. Also got "fresh" tires mfg 4011 (40th week of 2011). I'll keep you posted after our Fla trip in Feb.

[JimGolden]

Just a bit of trivia here....Michelin OWNS BF Goodrich. I'd bet you good money that many of the tires come out of the same plant. I have run BF Goodrich for years and never had a bit of trouble.

Other than being pricey, Michelin has always been an excellent tire for me as well. I routinely get 50,000 miles out of a set of Michelins.

Here's how the math works: 235/75-15

The width of the tire is 235mm. There are 25.4 mm to the inch so that would be 9.25 inches.

The aspect ratio is 75, which equals 0.75, which means 3/4 of the tread width. So, the sidewall height is equal to 235mm * 0.75 = 176mm = 6.94 inch.

The wheel diameter is 15". So if you want to know the overall height, it would be 15" + 6.94" + 6.94" (height of the sidewall for both top and bottom) = 28.87".

This actually isn't 100% correct as the tire does squash a little bit under the weight of the trailer. But this is the theoretical height and is pretty darn close.

I switched to LT tires on my triple axle the day I bought it and have never looked back.

Best of luck and see you on the road!

[perryg114]

Well I just got back from my second trip to Florida in a month. This trip we put about 1400 miles round trip. The tires have about 2500 miles on them total and they run cooler than the truck tires. I was running 70 MPH for the last couple hrs and no problems.

Perry

[Xenomorph]

Originally Posted by perryg114

Well I just got back from my second trip to Florida in a month. This trip we put about 1400 miles round trip. The tires have about 2500 miles on them total and they run cooler than the truck tires. I was running 70 MPH for the last couple hrs and no problems.

Perry

Nice!

[Andrew T]

Just by chance I picked up a 2000 30' Limited in Florida yesterday and it has Michelin 235's on it. I ran it 75 MPH for an hour in 81 degree temperatures yesterday afternoon. The tires on the left side were in the sun the other side shaded.

Drivers front tire on the truck was 118 Degrees, Rear was 126. Front drivers trailer tire was 109 and the rear was 115. The tires on the shaded side were all 3 or 4 degrees cooler except the for the front tire truck tire which was only 1 degree cooler than the drivers side (maybe an alignment issue)

I am afraid I won't have similar temps to test Marathons for a few months now.

Andrew T

[LI Pets]

Andy, were these 15"?