Tire Speed Rating Question
I'm posting this here because the speed rating of a tire seems to me to cross all lines/types of vehicles. Reading up on warranty issues/questions just now, I came across the following language ...
Forum Discussion
A couple of thoughts:
First, I am of the opinion that trailer manufacturers don't do a good job of sizing the tires on their trailers. I think they need to use tires that have at least a 15% unused capacity (in other words, no more than 85% of the tire's rated load).
So I don't think the vehicle tire placard for trailers is such a good stand alone value. I certainly wouldn't use anything less than what is there.
Second, the tables showing load vs inflation pressures are MINIMUMS!! You can NOT take that value by itself and use it. You SHOULD increase the inflation pressure ABOVE the value indicated - I think 15% more load carrying capacity - and I think that is 10 psi.
Third, I do not know of any vehicle tire placard that indicates a speed restriction for the vehicle. I think that is a good idea. I also think that speed restrictions should be plain and obvious - and they are usually just the opposite. Another shortcoming of trailer manufacturers.
And lastly, the 10 psi more to increase the speed restriction from 65 mph to 75 mph is on top of the load carrying capacity. So if you take my 15% and add 10 psi, you get 20 psi.
PS: One more thought: The burst pressure of tires is many times the maximum indicated on the sidewall of the tire. Put another way, tires do NOT fail because of the increased pressure (or at least the 10 psi values we are discussing. Please note, I am NOT advocating grossly over inflating tires, but within the limitations published by the tire manufacturers and tire standardizing organizations (which is what we are discussing), there are no failure issues involved.
First, I am of the opinion that trailer manufacturers don't do a good job of sizing the tires on their trailers. I think they need to use tires that have at least a 15% unused capacity (in other words, no more than 85% of the tire's rated load).
So I don't think the vehicle tire placard for trailers is such a good stand alone value. I certainly wouldn't use anything less than what is there.
Second, the tables showing load vs inflation pressures are MINIMUMS!! You can NOT take that value by itself and use it. You SHOULD increase the inflation pressure ABOVE the value indicated - I think 15% more load carrying capacity - and I think that is 10 psi.
Third, I do not know of any vehicle tire placard that indicates a speed restriction for the vehicle. I think that is a good idea. I also think that speed restrictions should be plain and obvious - and they are usually just the opposite. Another shortcoming of trailer manufacturers.
And lastly, the 10 psi more to increase the speed restriction from 65 mph to 75 mph is on top of the load carrying capacity. So if you take my 15% and add 10 psi, you get 20 psi.
PS: One more thought: The burst pressure of tires is many times the maximum indicated on the sidewall of the tire. Put another way, tires do NOT fail because of the increased pressure (or at least the 10 psi values we are discussing. Please note, I am NOT advocating grossly over inflating tires, but within the limitations published by the tire manufacturers and tire standardizing organizations (which is what we are discussing), there are no failure issues involved.
