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Desert_Captain's avatar
Desert_Captain
Explorer III
Aug 22, 2015

ST tire speed ratings

On our last trip near the end I checked the (bias ply), tires on the utility/motorcycle trailer while fueling and discovered one had suddenly developed serious cupping issue and the other now sported a bald section. No idea as to how many miles were on them beyond the 2,500 I had recently added but they had both looked OK the day before. :h (definitely time to check the axles alignment).



It was Saturday afternoon In Socorro NM and none of the three local tire shops had my size. The spare that came with the trailer was brand new but unfortunately the wrong size for the allegedly upgraded tires that were now failing {my bad for not being aware of that} :S

I remembered that some Wal Marts have a tire department or least sell trailer tires mounted on a rim so off to Truth Or Consequences, 60 miles down the road we went. The Walmart did have a tire shop but it was completely backed up late on Saturday afternoon so I bought two on rims off the shelf for $97 a piece. No doubt they are China bombs but were fairly new according to the DOT dates.

I carry all of the requisite tools so changing them out in our site at Elephant Butte SP was no problem. I torqued them to 70# each which a later re torque confirmed was holding just fine. Now I have two extra rims, albeit with crappy tires on them and a worthless spare. Decided to carry two spares from now on and the Wally World off the shelf tires will fill that niche... once I have them properly balanced.

I am buying a pair of Maxis' for the original wheels and I've ben shopping on line and then this morning at a couple of tire stores and got a bit of an education. It seems the old rule that ST tires are speed rated to a max of 65 mph is no longer necessarily true. Carlisle RH Radials and a few others I checked are rated for 87 mph. The Maxis' are still rated for 65 but since I never tow that fast and given their history of reliable performance (put a set on our 22' TT several years ago with great results), I elected to stay with the Maxis'.

My trailer takes a 175 80 (D), 13" which is well above the mere 960# the Cat Scale showed for the loaded trailer weight and trailer capacity is 1,600#. Thought about replacing with LT's but they don't make them that small. My local tire shop (Fletcher Tires), will be putting them on onTuesday and as a courtesy balancing the two from Wal Mart. The OTD price was $189 ($43 less than Discount Tire).

:C
  • trail-explorer wrote:
    I saw some ST tires with an "I" speed rating designation - 75mph. Regardless of speed rating, I'd never tow that fast. Fuel MPG goes down exponentiually as I get over 65 mph.


    It actually goes down by the inverse square rule when you begin moving forward :D
  • I'll still go to LT's on my trailers and wait'n see how these new speed limits
    play out

    Might be a better design now for cruising at 60-65 MPH...
  • JIMNLIN wrote:
    My trailer takes a 175 80 (D), 13" which is well above the mere 960# the Cat Scale showed for the loaded trailer weight and trailer capacity is 1,600#. Thought about replacing with LT's but they don't make them that small.

    Another top grade option I use on all of my single axle trailers and even light weight tandem axle trailers that come with 13" tires/wheels is sell the 13" and buy 14" wheels and a mount P205/75-14 or similar size and load capacity tire .
    Tires on a single axle don't side scrub as a tandem axle trailer so the P metric with 44 psi works out great.


    +1 on this. I've used P tires on dual axle many times with no issues. Tire scrubbing has never been a problem.

    Cue the ST fans. ;)
  • I saw some ST tires with an "I" speed rating designation - 75mph. Regardless of speed rating, I'd never tow that fast. Fuel MPG goes down exponentiually as I get over 65 mph.
  • My trailer takes a 175 80 (D), 13" which is well above the mere 960# the Cat Scale showed for the loaded trailer weight and trailer capacity is 1,600#. Thought about replacing with LT's but they don't make them that small.

    Another top grade option I use on all of my single axle trailers and even light weight tandem axle trailers that come with 13" tires/wheels is sell the 13" and buy 14" wheels and a mount P205/75-14 or similar size and load capacity tire .
    Tires on a single axle don't side scrub as a tandem axle trailer so the P metric with 44 psi works out great.
  • I actually just talked to Carlisle this past Fri, and as I had posted in a different thread (maybe you missed it), the RH tires, 15" are now rated at 81mph due to a govt tarriff placed on imported 15" tires with an 87mph. So they changed the rating of the 15". The 16" are rated at 75mph, and if I remember right, the 14" are 87mph, but not sure if they were changed due to the tarriff like the 15".

    Great catch on the tires! That could have been bad.

    Hope the Maxis work well for you. I have considered them myself in the past, just have never pulled the trigger on a set yet.
  • The cupping may have come from a Balancing problem.
    Bald spot probably alignment like you said.

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