Tired of ST tire blow outs , going to all LT tires

[Degolyerent]

I have had nothing but problems with ST tires, I also have changed to LT and no problems since. ST tires are a waste of time and money and like others have said to risky with expensive equipment.
John

 

[wolfpack2]

I think the duty cycle has to do with speed vs. load. If you are at the max load, reduce you speed to 80% of max (52 MPH). If you are at max speed (65 MPH) reduce load capacity by 80%. Sidewall deflection generates heat which is what kills tires. The higher the speed, the more flex cycles = more heat. The higher the load, the more the sidewall flexes = more heat. So slow down or reduce your load if you want the cheap ST tires to last or drive really short distances and let them stay cool.

 

[3930dave]

Sidewall flex is a big issue. Under-inflation is a fast killer of tires.

Your 80% Rule is the best explanation I've seen so far of this ST mess wolfpack2. But, I'd consider that as a pure de-rating issue, not so much duty-cycle related.

This part of the thread reminded my of something I read on TireRack, concerning deliberately Over-Inflating ST Tires, for higher speed operation. The caveat seems to be - Watch the Max Pressure rating of the Wheel itself.

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Special Trailer (ST) Tire Speed Ratings

Industry standards dictate tires with the ST designation are speed rated to 65 MPH (104 km/h) under normal inflation and load conditions.

However Goodyear Marathon and Power King Towmax STR tires featuring the ST size designation may be used at speeds between 66 and 75 mph (106 and 121 km/h) by increasing their cold inflation pressure by 10 psi (69 kPa) above the recommended pressure for the rated maximum load.

Do not exceed the wheel's maximum rated pressure. If the maximum pressure for the wheel prohibits the increase of air pressure, then maximum speed must be restricted to 65 mph (104 km/h).

The cold inflation pressure must not exceed 10 psi (69 kPa) beyond the inflation specified for the maximum load of the tire.

Increasing the inflation pressure by 10 psi (69 kPa) does not provide any additional load carrying capacity.

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Tire Tech Information - Trailer Tires vs. Passenger Vehicle Tires

I'm still a bit surprised by what TireRack has posted, but they have had this info up for a while now. If nothing else, it reminds me to never run ST tires at less than Max Pressure.

When I sourced my Greenball ST tires, and various times later, I have done a ton of reading about ST Tires. Other than the TireRack info I just linked, and wolfpack2's summary of (for Purchase Only) Engineering Standards, there is very little information out there concerning these severe limitations of ST tires.

I really can't understand why there haven't been major successful lawsuits over ST blowouts. While I'm no fan of frivolous lawsuits, I don't consider multi-ton trailers regularily blowing almost-new ST tires at highway speeds to be frivolous.

Even if you don't consider the base ST specification to be negligent (I do), then it is pretty easy to argue that the tire manufacturers and the whole trailer industry has been negligent in communicating these very serious ST tire limitations to consumers.

Rgds, D.

 

[mjw357]

Being in the trailer business part time one of the biggest issues I see with trailer tires is the valve stems. Demand high pressure metal stems. The standard rubber stem is only good to 50 psi. Tire heats up pressure builds then is released by underrated stem causing an under inflation situation leading to tire failure.

Chris

Yup, when I replaced the tires on my horse trailer, I put in new metal HP stems. Cheap insurance, and they look nice!

 

[Eric_Phillips]

It sounds like most of the people in these tire threads are pulling big heavy trailers. I have a 5,000lb flat bed and a 7,000lb horse trailer both are dual axle. Are the same problems seen on these lighter trailers? The E rated tires seem to be high overkill for trailers this size. If I did want to go with the higher rated tires how do I determine the max pressure of the rim?

 

[mjw357]

It sounds like most of the people in these tire threads are pulling big heavy trailers. I have a 5,000lb flat bed and a 7,000lb horse trailer both are dual axle. Are the same problems seen on these lighter trailers? The E rated tires seem to be high overkill for trailers this size. If I did want to go with the higher rated tires how do I determine the max pressure of the rim?

Might be some information stamped on the rim.

 

[Sprinklerman]

It sounds like most of the people in these tire threads are pulling big heavy trailers. I have a 5,000lb flat bed and a 7,000lb horse trailer both are dual axle. Are the same problems seen on these lighter trailers? The E rated tires seem to be high overkill for trailers this size. If I did want to go with the higher rated tires how do I determine the max pressure of the rim?

A blow out is a blow out , you haul horses ? Even more reason to have more tire than what is recommended.

 

[3930dave]

It sounds like most of the people in these tire threads are pulling big heavy trailers. I have a 5,000lb flat bed and a 7,000lb horse trailer both are dual axle. Are the same problems seen on these lighter trailers? The E rated tires seem to be high overkill for trailers this size. If I did want to go with the higher rated tires how do I determine the max pressure of the rim?

I've seen major tire problems on 3,000# trailers.

You'd need to verify the rim rating with the manufacturer. As a few guys have posted about here, the rubber valve stem itself is a common weak link - plan on upgrading the valve stems, esp. if you are significantly upping the pressure.

If you want to go to LT tires, any decent tire shop should be able to get the right rims for you. Watch the clearances, today's LTs can be too much tire for some smaller trailers.

Rgds, D.

 

[Rotax]

How fast are you guys pulling your trailers to be blowing out ST tires? You do realize they have a max speed rating of 65 MPH right? I have had great luck with ST tires, but I always see people on the highways doing 70-90 MPH pulling trailers only to have tires blow out on them. Not only is that way to fast for the tires to handle, it is extremely unsafe! Makes me shake my head.

 

[3930dave]

How fast are you guys pulling your trailers to be blowing out ST tires? You do realize they have a max speed rating of 65 MPH right? I have had great luck with ST tires, but I always see people on the highways doing 70-90 MPH pulling trailers only to have tires blow out on them. Not only is that way to fast for the tires to handle, it is extremely unsafe! Makes me shake my head.

I agree that some people are driving way too fast with certain loads.

An issue in the USA is that plenty of interstates have a 75mph limit.

State Speed Limit Chart | Speed Limits

Allowing ST tires to be produced/sold with a 65mph limit is just asking for trouble.

I prefer the backroads, but at times Interstates are convenient/necessary. Driving at 62mph on a 75mph limit highway can create it's own safety issues.... and many who don't understand the ST limit will just drive 80mph with the rest of the traffic.

When even the cheapest P tire you can buy has a better speed rating than ST tires, this legislation needs to change. Until that happens, LTs are a more bulletproof solution, IMO.

Rgds, D.