question on tire research

GrumpyandGrandma wrote:

Me Again wrote:

GrumpyandGrandma wrote:
Most RV tire issues are not due to where the tire came from, but from improper loading, under inflation and speed. 99% of all ST tires (US made included) are speed rated at 65. As to using LT on a tandem axle set-up, it is not recommended due to the side wall flex in hard turns. LT's have been known to pop off the rim in a hard turn due to the stiffer sidewall. The other big issue with ST tires is how long the unit has sat on a dealers lot (usually gravel) without moving before it is sold.

What a crock! ST tires fail at a high rate because they are a bottom tier cheaply made product, that we designed for utility trailers and local service. Some brainyact decided that one could see America with them on large heavy tall trailers.

Chris

You have your oppinon which if fine, but all you have to do is "research the facts". I camp with two very large clubs that are composed of 95% trailers and fw and the members do not have a large tire failure rate. Those that do are usually at the 5 to 6 year age range.

Here is some of the info

Trailers will be more stable and pull better on tires designed specifically for trailer use. Since Special Trailer (ST) tires are constructed with heavier duty materials, they are tougher than typical passenger vehicle tires. This is a plus because trailer suspension systems are generally stiffer and less sophisticated than automotive suspension systems.

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.

This is the first I have seen anyone claim that overinflating a ST tire will increase its speed rating. Please give a link to the *manufacturer's* site that says this. Sorry, that's a bit hard to believe.

Of course heavier trailers will have more failures. Look at the math:

My trailer weighs 13,500 lbs. The weight on the trailer axles is 11,300 lbs (CAT scale weight). I have Towmax "E" tires, weight rating 3,500 lbs. Ok, 11,300 / 4 = 2,875 lbs. That is 82% of the rated capacity of each tire. If I inflate to 80psi (which I do), then I have close to a 20% margin between actual and rated weight. If you consider that all 4 wheels carry more or less than a quarter of the weight, it is unlikely the variance will be more than 630 lbs (the difference between tire rated load and computed weight). So, I feel fairly safe with the Towmax, ST's at least for now.

Many rigs are carrying too much weight. When you are over 90% of rated capacity and under inflate by even a few pounds, the tire is bearing more than its rated load. Driving over 65 generates heat and stress that will lead to failure at some point. The key is to get your rig weighed fully loaded and calculate the tire load. Also, we have a TPMS and watch temp and pressure throughout the trip. We never leave without assuring we are at 80 PSI.

Could we still have a failure? Yes, of course. But we are doing all we can to avoid it. Next year, if we can afford it, I plan to change to 17 1/2" wheels and Goodyear 114's. While technically LT's, they are rated for use on trailers. They are G rated so there are more ply's than on my "E" Towmax. Since they are technically LT's, they have a speed rating of 75 MPH. We will NOT be driving that fast. Currently we stay at 60 or less. If we upgrade, I can see doing 65 sometimes. It's unsafe, according to Ford, to tow any faster than that.