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Old 08-19-2015, 11:36 PM   #21
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Pirelli, Goodyear and Toyo all attempted to make a fabric sidewall medium truck radial tires. All were 6-10 ply sidewalls with 3-5 radial belts over the tread, all were 12-16 ply rated load range. None worked and were discontinued. The sidewall should tell you how many body plies and belts are there.
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Old 08-20-2015, 07:27 PM   #22
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If you read the fine print none of the tires have actual 10 or 12 or 14 ply sidewalls. They have 10 ply or more EQUIVALENT side walls which I believe is about three actual plies. A well designed trailer tire has thinner tire walls to allow flexing from carrying a heavy load with less heat build up from the flexing as I understand it.
I am wrong about the sidewall stiffness of trailer tires so pls accept my apology for misleading. Here is an excerpt from the Carlisle manual about trailer tires:

From a highway blowout to a construction trailer flat on the work site,trailer tire failure is an inconvenience that can be avoided. Use thecorrect tires, calculate the correct load and maintain the right inflationto avoid problems.
Use the Right Tire
Trailer tire requirements differ greatly from automotive or light truck tires. Trailer tires are designated “ST” for Special Trailer tires. Automotive tires are designated “P” for Passenger or “LT” for LightTruck and are not designed for trailer use. Passenger or truck tires,with their more flexible sidewalls, can result in trailer sway problems.The stiffer, heavy duty sidewalls of ST tires are designed to controland reduce sway problems. Trailer sway is dangerous at higherspeeds, with top heavy loads or on vehicles with inadequatetongue weight.– Trailer tires are designed for use on trailer axle positions only.– Do not use P Passenger or LT Light Truck automotive tireson trailers.– Do not use ST trailer tires on passenger cars or light trucks.– An "LT" designation, when shown on a trailer tire size specifies loadrange only, it is not designed for use on light trucks.
The ST Difference
The construction, design, materials and testing used in ST SpecialTrailer tires meet the higher load requirements, duty cycles andspecial demands of trailering.– Polyester cords in an ST tire are bigger than in a comparable P orLT tire.– Steel cords used in ST tires have a larger diameter and greatertensile strength to meet additional load requirements.– ST tire rubber compounds contain chemicals to resist weather andozone cracking, particularly conditions resulting from extendedstorage and the unusual duty cycles of trailer tires.– The slightly shallower tread depth of a trailer tire reduces sway andrides cooler, which adds to tire longevity.– ST tires feature stiffer sidewalls, especially in the lowersection which:– Reduces sidewall flexing causing the trailer to track straighter.– Diminishes the risk of trailer sway.– Lessens the risk of sidewall puncture and blowout.– ST tires generally offer approximately 10% percent more loadcapacity than a similar LT tire and nearly 40% more than a Ppassenger tire.
Bias vs. Radial
Some ST trailer tires are bias-ply tires, which have crisscrossing cordsof polyester and/or nylon. Trailer tires are also offered in radialconstruction. Radial trailer tires feature plies that run perpendicularlyacross the tire, with belts (some made of steel) running underthe tread.
92
PRICES AND PRODUCT SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE. PRODUCT AVAILABILITY SUBJECT TO INVENTORY.
– Bias-ply trailer tires are recommended for tough, ruggedperformance and sidewall puncture resistance such as trailers usedfor construction, agriculture and some marine applications.– Radial tires are recommended when smooth ride, tread wear, heatand extended tire life are important considerations. Depending uponthe trailer duty cycle (storage time vs. actual time in use under load)the mileage expectation of radial trailer tire can be from 5,000 to12,000 miles. However, under well maintained conditions, properinflation and correct loads, considerably higher miles havebeen reported.
Load Limits
Trailers are used for one purpose, transporting loads. A major causeof trailer tire failure is overloading. It's important to know the weightof the actual load of the payload under tow, including all the toys,equipment, gas, gear, water and the trailer itself. An over-loaded tirewill produce excessive heat in the sidewall and tread which canquickly cause tire degradation or blowout. Excessive heat is thenumber one cause of trailer tire failure. The problem increases insunbelt areas where roadway surface temperatures are well abovenormal conditions. All tires are manufactured to handle specific load limits, but in towingtrailers, loads are the single greatest concern. Review the tiresidewall information and the vehicle owner's manual for vehicle loadlimits and proper tire inflation. Never exceed the maximum load ratingstamped on the tire sidewall or the maximum vehicle load rating,whichever is less. If possible, try to distribute the load evenly acrossall tires so that no single tire is overloaded. Tongue weight, tongueheight and especially load leveling hitches must be set properly toavoid overloading the trailer tires.ST tires are branded with a load range (LRB, LRC, LRD, LRE and LRF)on the sidewall, listing load range letters in the sidewall description.For example, ST205/75R15LRD.Discuss specific trailer uses to select the ST tire that is load rated forthe situation.– All tires must be identical in size for the tires to properly manage theweight of the trailer.– The combined capacity of the tires must equal or exceed the Gross Vehicle Weight (GVW) of the axle.– The combined capacity of all of the tires should exceed the loadedtrailer weight by 20 percent.– If a tire fails on a tandem axle trailer, replace both tires on that side.– If the tires are replaced with tires of a larger diameter, the tongueheight may need to be adjusted to maintain properweight distribution.
Inflation
Underinflation is the number one cause of trailer tire failure. Lowinflation pressure elevates tread temperature, especially as speedincreases. A tire can lose up to half of its air pressure and not appear


Radial Trail RH Trailer Tire

Refer to pages 92 and 93 for full story
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Old 08-21-2015, 11:23 AM   #23
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This makes it sound like ST tires are "special". That is BS!
While original designs made in the U.S. used heavier, different materials, today that is just not true. Today's ST tire is actually lighter than a "P" passenger tire made in the U.S. I did a seminar at the Airstream Rally where we had actual examples.

The ST increased load capacity does not come from construction but from reducing the speed rating. By reducing speed you increase load capacity. Example: look at the Goodyear LT235/85R16 G G614 which has a load capacity of 3,750 lbs. @ 75 mph and the Westlake ST235/85R16 G, load capacity of 4,075 @ 65 mph. Give me a tire with a higher speed rating with me running at a lower speed every time.

This is the case for all tires. Heavy equipment tires that are rated for 30 mph can have up to 5x the load capacity when used at creep speed(2.5 mph).

Having been in the tire business for 40 years, all the mis information out there really Pis&^#@* me off. I do not blame the consumer but companies like Carlisle are just plain full of it!
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Old 08-21-2015, 02:33 PM   #24
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Originally Posted by Titan Guy View Post
This makes it sound like ST tires are "special". That is BS!
While original designs made in the U.S. used heavier, different materials, today that is just not true. Today's ST tire is actually lighter than a "P" passenger tire made in the U.S. I did a seminar at the Airstream Rally where we had actual examples.

The ST increased load capacity does not come from construction but from reducing the speed rating. By reducing speed you increase load capacity. Example: look at the Goodyear LT235/85R16 G G614 which has a load capacity of 3,750 lbs. @ 75 mph and the Westlake ST235/85R16 G, load capacity of 4,075 @ 65 mph. Give me a tire with a higher speed rating with me running at a lower speed every time.

This is the case for all tires. Heavy equipment tires that are rated for 30 mph can have up to 5x the load capacity when used at creep speed(2.5 mph).

Having been in the tire business for 40 years, all the mis information out there really Pis&^#@* me off. I do not blame the consumer but companies like Carlisle are just plain full of it!
With all that said, I'm guessing that when you pull that heavy Redwood weight over 65 mph on a "E" Marathon that the load capacity is much lower? That might explain the bad rap the Marathons have gotten considering most RVs come with the Marathons and most toyhaulers and Rvers fly by me on the highway when I am doing 55 -60 mph.
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Old 08-21-2015, 02:42 PM   #25
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Rick you are correct. As speed increases from the approved speed rating the load capacity of the tire decreases.

One other thing that Carlisle states that I believe in but, have never seen it in print before is:
"The combined capacity of all of the tires should exceed the loaded trailer weight by 20 percent." Check out you passenger car tires, they all have a 20% or more margin for error. With the weights we are seeing out of the Rally Weigh In, the only tire that will give you that margin is the 215/75R17.5 H.
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Old 08-22-2015, 02:08 PM   #26
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Rick you are correct. As speed increases from the approved speed rating the load capacity of the tire decreases.

One other thing that Carlisle states that I believe in but, have never seen it in print before is:
"The combined capacity of all of the tires should exceed the loaded trailer weight by 20 percent." Check out you passenger car tires, they all have a 20% or more margin for error. With the weights we are seeing out of the Rally Weigh In, the only tire that will give you that margin is the 215/75R17.5 H.

Ron..............you just confirmed my suspicions. I have chosen to maintain my towing speed in the range of 55 to 65 mph except in a very rare circumstance. Right or center lane and let the rest of the traffic fly by at 80 mph.

Thanks for your comments.
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Old 08-22-2015, 03:55 PM   #27
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I always watch my tires in the rear view mirror, and it was always amazing how much bounce in the sidewall there was with an ST tire. Good or bad, they looked like my firestone airbags in the pin box going down the road. There were times they looked like they were going to bust!

The G614 just seems to run like a a regular tire. I'm sure pressure has some to do with it, but the sidewalls barely move.

Interesting letter from Goodyear (attached) about increasing air pressure 10 psi above tire inflation chart when running a Goodyear ST trailer tire (Marathon) at 75 mph which is beyond the 65 mph speed rating of the tire. That catch is, you still cannot exceed the maximum cold inflation pressure for the maximum load of the tire (i.e. 3,480 lb @ 80 psi) - many folks probably didn't read that far.

Technically, if a guy is only loaded to 3,000 lbs per tire or 6,000 lbs per axle and he is running ST235/80R16 LRE Marthons, he can run 75 mph according to Goodyear. Probably not possible in a Redwood because of weight, but I bet may of the lighter trailers out there meet this criteria, providing they are using the load range E Marathons and not load range D.
Attached Files
File Type: pdf Marathon ST trailer tire info 27 Mar 2006.pdf (64.1 KB, 18 views)
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Old 08-23-2015, 05:25 AM   #28
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I always watch my tires in the rear view mirror, and it was always amazing how much bounce in the sidewall there was with an ST tire. Good or bad, they looked like my firestone airbags in the pin box going down the road. There were times they looked like they were going to bust!

The G614 just seems to run like a a regular tire. I'm sure pressure has some to do with it, but the sidewalls barely move.

Interesting letter from Goodyear (attached) about increasing air pressure 10 psi above tire inflation chart when running a Goodyear ST trailer tire (Marathon) at 75 mph which is beyond the 65 mph speed rating of the tire. That catch is, you still cannot exceed the maximum cold inflation pressure for the maximum load of the tire (i.e. 3,480 lb @ 80 psi) - many folks probably didn't read that far.

Technically, if a guy is only loaded to 3,000 lbs per tire or 6,000 lbs per axle and he is running ST235/80R16 LRE Marthons, he can run 75 mph according to Goodyear. Probably not possible in a Redwood because of weight, but I bet may of the lighter trailers out there meet this criteria, providing they are using the load range E Marathons and not load range D.
I think your misreading the letter. As long as you don't exceed the max load rating, you can inflate to 90psi and travel at 75mph. This has been mentioned in TL mag.

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Old 08-23-2015, 06:21 AM   #29
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Ya you're right. But the point is the same, you can run ST tires at 75 mph by over inflating. Kind of bizarre.
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Old 08-23-2015, 03:26 PM   #30
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This makes it sound like ST tires are "special". That is BS!
While original designs made in the U.S. used heavier, different materials, today that is just not true. Today's ST tire is actually lighter than a "P" passenger tire made in the U.S. I did a seminar at the Airstream Rally where we had actual examples.

The ST increased load capacity does not come from construction but from reducing the speed rating. By reducing speed you increase load capacity. Example: look at the Goodyear LT235/85R16 G G614 which has a load capacity of 3,750 lbs. @ 75 mph and the Westlake ST235/85R16 G, load capacity of 4,075 @ 65 mph. Give me a tire with a higher speed rating with me running at a lower speed every time.

This is the case for all tires. Heavy equipment tires that are rated for 30 mph can have up to 5x the load capacity when used at creep speed(2.5 mph).

Having been in the tire business for 40 years, all the mis information out there really Pis&^#@* me off. I do not blame the consumer but companies like Carlisle are just plain full of it!
Tire temperature appears to be a useful indicator of tire loading and material integrity. Through your experience, what maximum temperature and rise in temperature above ambient road temperature have you seen stated?

Some of the current tire monitoring systems only display pressure. I can not remember the correlation of pressure rise to temperature rise.

Other tire monitoring systems display pressure and temperature. Once again, what would be reasonable operations ranges?

I utilize touch and/or infrared thermal devices to look for any tire with a reading above the average of the other tires. Not very accurate, yet I have found tires beginning to deteriate prior to failure.

Thanks.
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Old 08-23-2015, 05:25 PM   #31
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Tough question as each mfg. uses different reversion chemicals. Tire vulcanization occurs at 250'-320'. Reversion (the reverting of rubber from a solid to a liquid occurs at 250'. Some rubbers will revert at as little as 180'.
The consensus is ambient temperature + 60' is not unrealistic.

The problem is how you measure the temperature. I do no believe TPMS are accurate enough to be of any value. Infrared is much more accurate and should be measured in the shoulder area of the tire. Opinion only is I would not be concerned with a 40' temperature increase measured with infrared. This allows a margin of error.
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Old 08-23-2015, 06:24 PM   #32
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I guess I'm from the old school of touch, look and smell. I stop about every 100 miles and inspect my tires (and hubs because you can smell hot grease or brakes). I replace my tires before their life is up and all the years with big trucks and RVs I've only had 2 blow outs (One on the steer axle of a baffle-less tanker and the other on a rear tire of a Suburban). I believe inflation and balance is the key to maintaining tires.

I do think RV tires are more at risk for failure due to the amount of time they sit unused and sidewall bruising from hitting curbs as well as the twisting caused by tight backing.

I drive my equipment hard but I maintain to a stricter set of standards than most. So far this has worked very well for me.
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Old 08-23-2015, 08:19 PM   #33
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I as well am old school. I don't own a TPMS system or infrared device. I do own a accurate air pressure gauge. I know this because I calibrate it regularly. I do stop regularly and touch the tires just to make sure there is nothing excessively hot. I have noticed the Westlake's on the new 38GK seem to be running hotter than the G614 on my last 36RE. I have no way to prove this.
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Old 08-24-2015, 03:30 AM   #34
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I have the TST 507 TPMS unit. The factory preset high temp alarm is 158F. According to them that is the maximum according to Michelin, above that temps start to become serious. On my 36RE with GY 614s and 100psi cold I've seen 118F at 88F ambient. Pressure increased to 121psi. My high pressure alarm was set at 120 so it alarmed. It's now at 122, but haven't seen above 118 since.

I might go to 110psi now that I have the Flex Air and am about ready to install the SRE 4000.

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