Originally Posted By: CapriRacer
Originally Posted By: GC4lunch
The European speed system is a rating that is the same as the Temperature rating in the American Uniform Tire Quality Grading mandated by the NHTSA. It is a measure of one thing, and one thing only: the maximum temperature to which a properly inflated tire, loaded within its load limitations can attain before it will explode.
I'm sorry, but that is not correct.
I am not going to disagree with you, because I think that we are saying the samee thing from different directions. After I had posted the above, I attempted to revise it -- but was outside the short revision time period -- to say "... the maximum rotations per minute that a properly inflated tire, loaded within its load limitations can sustain before it attains an internal temperature that will cause it to explode ..." It is the speed that causes the temperture rise, and it is the temperature that causes the catastrophiic failure, but the causal chain is seamless.
Originally Posted By: CapriRacer
Both the speed rating and the UTQG Temperature ratings are not tied to temperature.
I diasgree; you are incorrect. The reason that the UTQG criterion is called the "Temperature rating" is because it is tied to temperature. The test procedures of both ratings systems are the same: running a tire against a rotating steel drum of specified diameter at a specified number of rotations per minute for a specified time period. If the tire fails before the end of the time period, the speed rating is not achieved.
Now, to design a tire that will pass the test, the tire manufacture can follow either or both of two strategies: it can design the tire to dissipate the heat that is generated more efficiently, or it can design the tire to withstand greater temperatures before the tire fails. Both strategies are directly related to temperature.
Originally Posted By: CapriRacer
Both tests are about the maximum speed a tire can attain before failure - and failure doesn't mean a loss of inflation pressure. It means loss of casing integrity. Typically, the failure is a "belt-leaving-belt" separation - and the air chamber is still intact.
In real-world conditions -- on the road, rather than in the testing chamber -- delamination is followed almost instantaneously by a loss of integrity of the air chamber: delamination on the road is followed so closely by explosion of the tire that they effectively are a single event.
Originally Posted By: CapriRacer
Originally Posted By: GC4lunch
..... The S, T, H, V, Z speed ratings simply indicate how many rotations per time period the properly inflated, not overloaded, tire can sustain before it will explode; the speed ratings mean nothing more or less than that......
In some repects that is correct, but more accurately, the speed rating is the speed that the tire can attain before failure. The tests are step speed tests, where the tire is subjected to increasing speed in a series of steps. You could look at that as either time or revolutions, but that's because the test has that defined, but the way this is always reported is a speed.
The way it is reported is as a grade: C, B, or A for the UTQG, or S T, H, V... for the ECE speed ratings. The ECE speed ratings provide a table for the maximum vehicle speed associated with each letter, but that table is a translation of revolutions per minute when the tire is run against the steel drum in the lab, using a mathematical formula. The tire under test in the lab is applied to an axle that is stationary; no actual speed is involved.
Originally Posted By: CapriRacer
Temperature is NOT the criteria used to determine the speed rating.
I am sorry, but that is nonsensical: the tire fails when it attains a temperature that exceeds its design parameters to dissipate heat or when the heat reaches a temperature where it exceeds the tire's design parameters to retain integrity. The temperature need not be measured in degrees, because the temperature is more directly measured by the tire's failure, but temperature ultimately is the only criterion used to determine the speed rating.
Originally Posted By: CapriRacer
Originally Posted By: GC4lunch
.... Obviously a stiffer sidewall will flex less than a more flexible sidewall, for instance, and rayon carcass plies will generally perform batter than polyester carcass plies........
I disagree. There are a number of different materials that could be used for the plies, but they don't impact that speed rating. The casing is the same for an S rated tire and an H rated tires. The difference is the cap plies.
Here we have a direct disagreement. Rayon is superior to polyester as a material for tires because of its linear characteristics over a wider range of temperatures than polyester. Again, temperature is the crucial factor. The number of cap plies is not specified in either the European or the NHTSA speed rating rules or testing procedures, and there is an implication in the ECE-30 language that (theoretically, at least), a bias ply tire with no cap plies could achieve any speed rating.
Originally Posted By: CapriRacer
Originally Posted By: GC4lunch
....... But there are no hard and fast rules. For example: the Continental ExtremeContact DW tire has a single polyester ply carcass construction, and has a relatively flexible sidewall therefore, and a relatively soft ride; but the 'DW is a Z-rated tire, albeit a tire that never, ever, should be driven underinflated, because it heats up very rapidly when driven at high speed when underinflated......
I think you will find that the larger tires will have 2 plies regardless of the tire line - and by larger, I mean load carrying capacity - and Load Index is a short cut to that value.
Actually, the tire I used as an illustrative example, the Continental ExtremeContact DW, has high specified load levels compared to other tires of similar sizes. It has a single sidewall ply.
Originally Posted By: CapriRacer
... in order to pass the higher speed ratings, the tire has to have more cap plies. You could call it a "Rule of Thumb", but it's a generalization about how things are currently done.
Now you're just making things up.
Originally Posted By: GC4lunch
The European speed system is a rating that is the same as the Temperature rating in the American Uniform Tire Quality Grading mandated by the NHTSA. It is a measure of one thing, and one thing only: the maximum temperature to which a properly inflated tire, loaded within its load limitations can attain before it will explode.
I'm sorry, but that is not correct.
I am not going to disagree with you, because I think that we are saying the samee thing from different directions. After I had posted the above, I attempted to revise it -- but was outside the short revision time period -- to say "... the maximum rotations per minute that a properly inflated tire, loaded within its load limitations can sustain before it attains an internal temperature that will cause it to explode ..." It is the speed that causes the temperture rise, and it is the temperature that causes the catastrophiic failure, but the causal chain is seamless.
Originally Posted By: CapriRacer
Both the speed rating and the UTQG Temperature ratings are not tied to temperature.
I diasgree; you are incorrect. The reason that the UTQG criterion is called the "Temperature rating" is because it is tied to temperature. The test procedures of both ratings systems are the same: running a tire against a rotating steel drum of specified diameter at a specified number of rotations per minute for a specified time period. If the tire fails before the end of the time period, the speed rating is not achieved.
Now, to design a tire that will pass the test, the tire manufacture can follow either or both of two strategies: it can design the tire to dissipate the heat that is generated more efficiently, or it can design the tire to withstand greater temperatures before the tire fails. Both strategies are directly related to temperature.
Originally Posted By: CapriRacer
Both tests are about the maximum speed a tire can attain before failure - and failure doesn't mean a loss of inflation pressure. It means loss of casing integrity. Typically, the failure is a "belt-leaving-belt" separation - and the air chamber is still intact.
In real-world conditions -- on the road, rather than in the testing chamber -- delamination is followed almost instantaneously by a loss of integrity of the air chamber: delamination on the road is followed so closely by explosion of the tire that they effectively are a single event.
Originally Posted By: CapriRacer
Originally Posted By: GC4lunch
..... The S, T, H, V, Z speed ratings simply indicate how many rotations per time period the properly inflated, not overloaded, tire can sustain before it will explode; the speed ratings mean nothing more or less than that......
In some repects that is correct, but more accurately, the speed rating is the speed that the tire can attain before failure. The tests are step speed tests, where the tire is subjected to increasing speed in a series of steps. You could look at that as either time or revolutions, but that's because the test has that defined, but the way this is always reported is a speed.
The way it is reported is as a grade: C, B, or A for the UTQG, or S T, H, V... for the ECE speed ratings. The ECE speed ratings provide a table for the maximum vehicle speed associated with each letter, but that table is a translation of revolutions per minute when the tire is run against the steel drum in the lab, using a mathematical formula. The tire under test in the lab is applied to an axle that is stationary; no actual speed is involved.
Originally Posted By: CapriRacer
Temperature is NOT the criteria used to determine the speed rating.
I am sorry, but that is nonsensical: the tire fails when it attains a temperature that exceeds its design parameters to dissipate heat or when the heat reaches a temperature where it exceeds the tire's design parameters to retain integrity. The temperature need not be measured in degrees, because the temperature is more directly measured by the tire's failure, but temperature ultimately is the only criterion used to determine the speed rating.
Originally Posted By: CapriRacer
Originally Posted By: GC4lunch
.... Obviously a stiffer sidewall will flex less than a more flexible sidewall, for instance, and rayon carcass plies will generally perform batter than polyester carcass plies........
I disagree. There are a number of different materials that could be used for the plies, but they don't impact that speed rating. The casing is the same for an S rated tire and an H rated tires. The difference is the cap plies.
Here we have a direct disagreement. Rayon is superior to polyester as a material for tires because of its linear characteristics over a wider range of temperatures than polyester. Again, temperature is the crucial factor. The number of cap plies is not specified in either the European or the NHTSA speed rating rules or testing procedures, and there is an implication in the ECE-30 language that (theoretically, at least), a bias ply tire with no cap plies could achieve any speed rating.
Originally Posted By: CapriRacer
Originally Posted By: GC4lunch
....... But there are no hard and fast rules. For example: the Continental ExtremeContact DW tire has a single polyester ply carcass construction, and has a relatively flexible sidewall therefore, and a relatively soft ride; but the 'DW is a Z-rated tire, albeit a tire that never, ever, should be driven underinflated, because it heats up very rapidly when driven at high speed when underinflated......
I think you will find that the larger tires will have 2 plies regardless of the tire line - and by larger, I mean load carrying capacity - and Load Index is a short cut to that value.
Actually, the tire I used as an illustrative example, the Continental ExtremeContact DW, has high specified load levels compared to other tires of similar sizes. It has a single sidewall ply.
Originally Posted By: CapriRacer
... in order to pass the higher speed ratings, the tire has to have more cap plies. You could call it a "Rule of Thumb", but it's a generalization about how things are currently done.
Now you're just making things up.