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Old 12-28-2019, 12:34 PM   #1
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Replace C load-rated with D?

I have a 2015 23FB International, and I experienced a blowout this week of one of the factory GY Marathon tires. 50 PSI maximum, C load-rated. I have the factory 14-inch wheels. Is there any safety issue replacing all the ties with D load-rated tires, with maximum 65 PSI inflation? Will the stock wheels and stems handle the additional tire pressure?
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Old 12-28-2019, 01:04 PM   #2
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No issues with D rated tires or the wheels at 65 psi. It will be safer IMO.

IMO you do not need 65psi. A harsh ride can do damage the trailer.

For my 25' I've always used higher psi than the tires load chart says is needed to carry the weight. Doing this decrease the tires' tendency for the sidewall to rollover sideways when twisting the trailer.

For a starting point, I would take the gross weight of the trailer, divide by four, multiply by 1.25. That is the maximum load I would assume would be on any one tire. Using that weight, I would use the tire manufacturers' tire load chart and inflate to their recommended pressure. Then experiment with using higher pressure above that point.
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Old 12-28-2019, 01:24 PM   #3
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I replaced the 14 inch with 15 inch Sendel T03 wheels on my 2014 23RB. Mounted Michelin 15 inch "D" rated tires. This has been a common retrofit of the 14 inch 23FB/RB trailers.
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Old 12-28-2019, 01:37 PM   #4
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D-rated tires

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Originally Posted by SilverWind View Post
I replaced the 14 inch with 15 inch Sendel T03 wheels on my 2014 23RB. Mounted Michelin 15 inch "D" rated tires. This has been a common retrofit of the 14 inch 23FB/RB trailers.
Thanks. What tire pressure do you use?
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Old 12-28-2019, 01:51 PM   #5
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Adjusting tire pressure to match load rating with actual load for the range of expected temperatures is one key to avoid tire failure.

Summary: You can safely switch to D load rated tires so long as you adjust the pressure to match actual load for the temperatures you expect to experience.

Under inflation for actual load allows excessive sidewall flex causing the tire to overheat, separate and fail. Over inflation reduces flex, but if the ambient and road temperatures are high can cause tire pressure to exceed the tire's physical limit resulting in failure also.

Speed rating is another factor almost as important as load rating. It is a function of flex, heat generation and efficiency of transferring the heat build up to the road and air away from the tire. The faster the tire spins, the more it flexes and builds up heat. At some speed the heat build-up reaches what the industry standard for the safe operating limit of the tire material and design, this is the speed rating. I won't go into the testing and certification process but suffice to say that many tires have conservative speed ratings, though there is no good way to know which ones so follow the stated limit.

Okay here are some tire inflation tips:

Slightly over inflating tires to near or at the maximum rated cold temperature for the maximum ambient temperature you expect to experience during that trip or inflation period will always reduce heat build up and avoid risk of failure due to under inflation. The trade off is it will slightly reduce traction and increase uneven tire wear.

Inflating tires to the maximum rated cold temperature on a cool morning or cold location and then driving near the tire's maximum speed rating during a drive though a much warmer ambient air and road temperature (hot sunny day for example) must be avoided. This is likely the most common way to experience a blow out. Instead before making the trip, reduce the cold inflation temperature by 1 psi for every 7 degrees Fahrenheit higher ambient you expect to experience during the trip is a good physics based rule of thumb to use. You can also let out the same one psi for every 7 degrees from a hot tire as you transition to a warmer environment, but only do this if you know your cold tire pressure was too high. If you don't know your baseline, it's best not to let air out unless the actual hot pressure is well above the maximum rated cold tire pressure.

It probably goes without stating, but never run your tires below the cold pressure recommended for the actual load based on the load capacity vs. cold pressure table for the load range tire you have. You can google for tables online for your tire. Note though, the load ranges are specific to the tire type. Load ranges for Passenger tires, P, are often different than Light Truck, LT, and (Special) Trailer, ST. These are DOT designations. Other countries often have there own designations.

Multiple axles complicate load ratings as does dual tires on the same axle. Ask if you want that explained.
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Old 12-28-2019, 02:18 PM   #6
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Folks have reported they replaced the 14s with the new generation GY-Endurance tires. Have not seen any negative posts yet.

Lots of info out there on the 14-15in switch. It's an easy way to get a bit more ground clearance as well as more load capacity.

Enjoy that 23. Pat
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Old 12-28-2019, 02:27 PM   #7
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The stock wheels and stems will be fine for the higher pressure. If the stems are rubber it's good insurance to replace them unless you inspect them carefully for defects.

Many people suggest a switch to Light Truck tires for their trailers, but others don't. One advantage of most Special Trailer tires is they have extra sidewall protection against scuffing from hitting curbs. The tread design is also optimized for breaking traction as a passive towed wheel.
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Old 12-28-2019, 02:36 PM   #8
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The stock wheels and stems will be fine for the higher pressure. If the stems are rubber it's good insurance to replace them unless you inspect them carefully for defects.
IMO would replace all stems w/metal, plus vandals can slice rubber at rim then fun starts to find flat, then fix flat. When sliced you can not see cut.
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Old 12-28-2019, 02:50 PM   #9
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I would do what I always do.

Increase rim size to 15 and put on light truck tires. Those trailer tires are just not as strong.
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Old 12-28-2019, 02:54 PM   #10
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Originally Posted by A W Warn View Post
No issues with D rated tires or the wheels at 65 psi. It will be safer IMO.

IMO you do not need 65psi. A harsh ride can do damage the trailer.

For my 25' I've always used higher psi than the tires load chart says is needed to carry the weight. Doing this decrease the tires' tendency for the sidewall to rollover sideways when twisting the trailer.

For a starting point, I would take the gross weight of the trailer, divide by four, multiply by 1.25. That is the maximum load I would assume would be on any one tire. Using that weight, I would use the tire manufacturers' tire load chart and inflate to their recommended pressure. Then experiment with using higher pressure above that point.
This seems like sound advice gleaned from a lot of experience. I think I'll go with this plan in the future. I will adjust the cold pressures to account for specific trip ambient temperatures though. Thanks for the great guidelines.
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Old 12-28-2019, 04:09 PM   #11
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Thanks. What tire pressure do you use?
50psi
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Old 12-29-2019, 11:13 AM   #12
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In addition to the comments above, keep in mind that all tires have a life span of 4 - 5 years, regardless of tread depth. They deteriorate from the inside-out, so you cannot see it, and may have a false sense of security...
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Old 12-29-2019, 02:19 PM   #13
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The previous owner had Goodyear Marathon C rated 15" tires on the '86 Sovereign 25'. I replaced them with Maxxis D rated tires eleven years ago and they had been great. I will replace them before spring because they are past their prime. The fact they have done this well over the time period uncovered should tell you something.
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Old 12-29-2019, 04:31 PM   #14
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Older, lighter trailers can use lessor quality tires because the weight and turning forces are lighter. However, as the length and especially the weight increased through the years the tire demands have increased dramatically. The real reason for going to truck tires is the heavier duty specs including much thicker tread. As for tire pressure, unless you weigh each wheel and use that as a load vs. pressure basis you are just guessing at the ideal static cold inflation value. Therefor, it is best to air up to the maximum pressure stated on the sidewall. In the first eleven years with my three axle I went through twenty one tires. Marathons, Carlislea, Maxx, it did not matter. But now on the second set of Michelins zero tire problem. Be advised Airstream recommends changing the Mivhelins out every 5 years due to environmental exposure. Indoors storage does help tire life. I have nine years with B. F. Goodrichs on my garaged Nissan Extrra and they still have no weather cracks. Discount tire says they will not repair them when they become ten years old. Live and learn.
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Old 12-29-2019, 04:40 PM   #15
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Quote:
Originally Posted by hreniger View Post
keep in mind that all tires have a life span of 4 - 5 years, regardless of tread depth.

And you are basing that on what?
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Old 01-01-2020, 08:05 PM   #16
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Tires replaced - speed ?

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Originally Posted by DeanAir View Post
I have a 2015 23FB International, and I experienced a blowout this week of one of the factory GY Marathon tires. 50 PSI maximum, C load-rated. I have the factory 14-inch wheels. Is there any safety issue replacing all the ties with D load-rated tires, with maximum 65 PSI inflation? Will the stock wheels and stems handle the additional tire pressure?
I had the D load-rated tires installed. Any opinions as to whether they can be safely driven over 65 mph?
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Old 01-02-2020, 01:16 AM   #17
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And you are basing that on what?
Tire manufactures and tire engineers. A general consensus from various tire industry associations around the world is that tires have a useful service life of six to ten years.

My tire dealer will not touch, fix, rotate a tire older than 10 years old regardless of tread depth. I have had to replace 10 year old tires with only 10 or 12 thousand miles on them.

-Dennis
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Old 01-02-2020, 07:37 AM   #18
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Really?

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... They deteriorate from the inside-out, so you cannot see it, and may have a false sense of security...
I have never heard that before. The 25+ year-old tires pulled off my Overlander on Day 0 looked like a million bucks on the inside and definitely unsafe on the outside.

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Old 01-02-2020, 07:51 AM   #19
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I have never heard that before. The 25+ year-old tires pulled off my Overlander on Day 0 looked like a million bucks on the inside and definitely unsafe on the outside.

Tom
The problem with looking on the inside of a used tire is that you are looking at the innerliner and that is usually made from an air retaining rubber such as a halobutyl - and those don't crack like the types of rubber used throughout the rest of the tire. It's the rubber immediately under the ineerliner that is the one that is important and you can't see or detect a problem until it separates and causes a bulge. By then, it's too late.

The idea of looking at the outside, especially the sidewall, is to get an indication of what is going on deeper in the tire - and that is not reliable because some tire manufacturers use sidewall rubber that doesn't show it's age (and condition).

The best advice is to use the amount of time in service - and alternatively, how long it has been since the tire was manufactured.
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Old 01-02-2020, 07:55 AM   #20
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CapriRacer,

Thanks for taking the time to post an in-depth response. I hope the original poster reads it!

Tom
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