http://www.boatus.com/trailerclub/trailer_tires.asp
BoatU.S. Trailering spoke with experts at two trailer tire manufacturers: Goodyear (maker of Marathon radials) and Kenda (maker of Karrier ST Radials and Load Star bias ply tires).
How fast?
Industry standards dictate that ST tires are restricted to a speed of 65 mph unless a different speed restriction is indicated on the tire sidewall. If speeds from 66 to 75 mph are used, the tire cold inflation pressure can be increased by 10 psi without any increase in load. -
Goodyear Tire Company
Like a passenger car tire, which has a speed rating, trailer tires are also designed with a certain speed rating. However, the trailer tire is used to sustain the higher loading weight and will generate higher heat than the tire going at the same speed on a car. Since heat build up will potentially degrade a tire's structure and cause either a blow out or separation, trailer tires are usually designed at lower speed rating. -
Kenda Tire Company
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Since my 14" TM factory rims are rated to 1870lbs max, the assumption is the max pressure is then limited to 50psi. Increasing to 60psi would exceed the max pressure of my rims by 20%. For those using 14" Goodyear Marathon tires - only non-factory rims rated to 65psi will benefit from PSB#2011-13. But that would beg the question: if one has 14" non-factory rims rated to 65psi (load range D), why are you using Goodyear Marathon (load range C) 14" tires? Especially considering their history!