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Old 11-24-2011, 05:12 PM   #71
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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.
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Old 11-24-2011, 05:31 PM   #72
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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
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Old 11-24-2011, 06:42 PM   #73
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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.
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Old 11-25-2011, 01:17 AM   #74
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Originally Posted by Kamiak View Post
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
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Old 11-25-2011, 06:15 PM   #75
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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.
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Old 11-25-2011, 07:00 PM   #76
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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!
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Old 11-26-2011, 08:06 PM   #77
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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
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Old 11-27-2011, 01:09 AM   #78
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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!
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Old 11-28-2011, 02:27 PM   #79
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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
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Old 11-28-2011, 03:40 PM   #80
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Andy, were these 15"?
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Old 11-28-2011, 05:40 PM   #81
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I expect they were 235/75-R15 XL tires he is talking about.

Tires temps, what do they mean? I have felt of tires after highway driving in the summer and they were just about too hot to touch. So how do we know how hot is too hot? The tire industry must have some established limits? We see temperature A, B, C etc on the tire. C being a higher temp rating than A, I expect. So does that mean the tire can stand higher temps or is it constructed to not get as hot? The faster you drive the hotter the tire gets. The lower the air pressure the hotter it gets. Speed ratings are mainly based on temperature and not RPM. Any tire can go fast for short periods of time but it takes a speed rated tire to go 100+ for hours at a time.

The rubber is going to melt and start separating from the cords and belts and start to blister and then boom. Most car tires fail because the yahoo driving ran the tires with almost no air in them and they got too hot and came apart. I see folks driving around with tires that have about 10psi in them. I gave up trying to warn these folks because they act like you are nuts. These are the same yahoo's I see driving 80 MPH down the interstate on the way to work with a temporary spare on the front axel.

Perry
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Old 11-28-2011, 05:47 PM   #82
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The Michelin P235/75R15 M/S 2 I have are speed rated T. Guess I will have to slow down to accommodate.
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Old 11-29-2011, 07:26 AM   #83
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Here is an interesting article I found on setting tire air pressures. It applies to race cars mainly. What I learned from it is that you want the tire temperature to be even from edge to center. If the center temps are higher than the edge temps then you have too much pressure. If you way over inflate the tire then all the heat is going into the center of the tread. So just because you have an E rated tire does not mean that you should automatically run it at 80psi when it is only at 60% of the rated load. So the knee jerk run the max pressure all the time is probably not correct. On my cars and trucks I NEVER run at max psi unless I am at severe loads. On my Ranger truck I run about 20-25 psi in the rear and 35psi in the front. If I ran 35psi in the rear I would not be able to get any traction.

Tires - Tech, Guide - Temperature Readings - Popular Hot Rodding

Perry
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Old 11-29-2011, 07:33 AM   #84
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I was wrong on the temperature ratings. An A temperature rating is the highest.

Perry

Quote:
Originally Posted by perryg114 View Post
I expect they were 235/75-R15 XL tires he is talking about.

Tires temps, what do they mean? I have felt of tires after highway driving in the summer and they were just about too hot to touch. So how do we know how hot is too hot? The tire industry must have some established limits? We see temperature A, B, C etc on the tire. C being a higher temp rating than A, I expect. So does that mean the tire can stand higher temps or is it constructed to not get as hot? The faster you drive the hotter the tire gets. The lower the air pressure the hotter it gets. Speed ratings are mainly based on temperature and not RPM. Any tire can go fast for short periods of time but it takes a speed rated tire to go 100+ for hours at a time.

The rubber is going to melt and start separating from the cords and belts and start to blister and then boom. Most car tires fail because the yahoo driving ran the tires with almost no air in them and they got too hot and came apart. I see folks driving around with tires that have about 10psi in them. I gave up trying to warn these folks because they act like you are nuts. These are the same yahoo's I see driving 80 MPH down the interstate on the way to work with a temporary spare on the front axel.

Perry
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