LT tires on TT
I was telling a buddy of mine how I upgraded my TT tires from ST's to LT's (Michelin RIBS) and he would like to upgrade to LT's also. He asked if he could go to any LT tire as long as they had the cor...
Forum Discussion
There is a significant difference between the DOT testing requirements as covered in FMVSS 571 and the SAE high Speed rating (if a tire has one)
DOT does not speed rate tires. There are a number of different tests used by DOT. Some are "step speed" ie the load is held constant and the speed increases to some specified level for a tire to be considered as having "passed" that requirement. There are also "step load" ie the speed is constant but the load increases to some specified level for a tire to be considered as having "passed" that requirement. Most testing has some "warm-up" steps at different speed, time and loads.
The different speeds and different loads used during certification testing are not an absolute predictor of a tire's ultimate performance capability. Since the regulations require 100% compliance it is necessary for each tire company to decide how far above the minimum test requirements they need to test their tires. This "margin" is statistically developed and is intended to account for normal product variation. Sometimes it is even possible for this margin to be different for different types tires or possibly even different tire plants.
Having said this there is one bit of information that would help people select tires with possibly slightly better performance capabilities. This would be the "Service Description". Look on THIS page at the numbers after what you should recognize as the tire size nomenclature.
Most modern P type tires and many LT type tires have a Service Description as part of the size. The number is based on a table of the load capacity of the tire. The Letter is a "Speed Symbol"
you can read more about the service description HERE.
Quite frankly I see no reason to get wrapped up in the different regulatory test requirements as I would not consider them a meaningful tool to try and compare tires as you do not have access to the individual tire companies statistical methods.
DOT does not speed rate tires. There are a number of different tests used by DOT. Some are "step speed" ie the load is held constant and the speed increases to some specified level for a tire to be considered as having "passed" that requirement. There are also "step load" ie the speed is constant but the load increases to some specified level for a tire to be considered as having "passed" that requirement. Most testing has some "warm-up" steps at different speed, time and loads.
The different speeds and different loads used during certification testing are not an absolute predictor of a tire's ultimate performance capability. Since the regulations require 100% compliance it is necessary for each tire company to decide how far above the minimum test requirements they need to test their tires. This "margin" is statistically developed and is intended to account for normal product variation. Sometimes it is even possible for this margin to be different for different types tires or possibly even different tire plants.
Having said this there is one bit of information that would help people select tires with possibly slightly better performance capabilities. This would be the "Service Description". Look on THIS page at the numbers after what you should recognize as the tire size nomenclature.
Most modern P type tires and many LT type tires have a Service Description as part of the size. The number is based on a table of the load capacity of the tire. The Letter is a "Speed Symbol"
you can read more about the service description HERE.
Quite frankly I see no reason to get wrapped up in the different regulatory test requirements as I would not consider them a meaningful tool to try and compare tires as you do not have access to the individual tire companies statistical methods.
