Way too much B.S. in this thread. Speed rating has nothing to do with sidewall stiffens and everything to do with a nylon cap.
Ride quality difference in a H rated tire vs a V?
- Thread starter Blue_Goose
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Originally Posted By: friendly_jacek
Way too much B.S. in this thread. Speed rating has nothing to do with sidewall stiffens and everything to do with a nylon cap.
Can you explain further? Not being a smarty, just would like to know
Goose
Way too much B.S. in this thread. Speed rating has nothing to do with sidewall stiffens and everything to do with a nylon cap.
Can you explain further? Not being a smarty, just would like to know
Goose
Originally Posted By: friendly_jacek
Way too much B.S. in this thread. Speed rating has nothing to do with sidewall stiffens and everything to do with a nylon cap.
That's nice, but when you actually LOOK at the differences in tire models which come in several speed ranges you discover that the sidewall construction is often different as well.
Way too much B.S. in this thread. Speed rating has nothing to do with sidewall stiffens and everything to do with a nylon cap.
That's nice, but when you actually LOOK at the differences in tire models which come in several speed ranges you discover that the sidewall construction is often different as well.
Here's the problem:
When you compare tires WITHIN a given line, you'll find the sidewall construction might be different between speed ratings.
- BUT -
The difference between different tires (meaning brand / tire line) can be quite different in ride quality. Unfortunately there isn't a good rule of thumb - except to say that GENERALLY higher speed rated tires will have a stiffer ride. But there are enough exceptions to this rule to make it a non-rule.
When you compare tires WITHIN a given line, you'll find the sidewall construction might be different between speed ratings.
- BUT -
The difference between different tires (meaning brand / tire line) can be quite different in ride quality. Unfortunately there isn't a good rule of thumb - except to say that GENERALLY higher speed rated tires will have a stiffer ride. But there are enough exceptions to this rule to make it a non-rule.
Originally Posted By: Blue_Goose
Originally Posted By: friendly_jacek
Way too much B.S. in this thread. Speed rating has nothing to do with sidewall stiffens and everything to do with a nylon cap.
Can you explain further? Not being a smarty, just would like to know
Goose
To get a higher speed rating, the tire has to have more cap plies.
S and T rated tires don't need to have a cap ply.
H rated tires need to have one cap ply.
V and higher need to have 2 cap plies.
Notice this does NOT say anything about the sidewall construction.
Originally Posted By: friendly_jacek
Way too much B.S. in this thread. Speed rating has nothing to do with sidewall stiffens and everything to do with a nylon cap.
Can you explain further? Not being a smarty, just would like to know
Goose
To get a higher speed rating, the tire has to have more cap plies.
S and T rated tires don't need to have a cap ply.
H rated tires need to have one cap ply.
V and higher need to have 2 cap plies.
Notice this does NOT say anything about the sidewall construction.
Originally Posted By: CapriRacer
To get a higher speed rating, the tire has to have more cap plies.
S and T rated tires don't need to have a cap ply.
H rated tires need to have one cap ply.
V and higher need to have 2 cap plies.
Notice this does NOT say anything about the sidewall construction.
Slightly
Does this apply to all size tires? Would larger tires require more reinforcement than smaller tires for a given rating?
To get a higher speed rating, the tire has to have more cap plies.
S and T rated tires don't need to have a cap ply.
H rated tires need to have one cap ply.
V and higher need to have 2 cap plies.
Notice this does NOT say anything about the sidewall construction.
Slightly
Does this apply to all size tires? Would larger tires require more reinforcement than smaller tires for a given rating?
Goose, why not just take the rims in and get whatever tires you want put on them ?? .....
You know I thought of that but by the time all is said and done I think I will just get the V Primacy's The tire is an outstanding tire and I think it will give me a lot better ride than the GY's....V rated or not. The price is really a wash too with them meeting an internet price
You'll be surprised by the reduction in wheel weights required to balance the Mics too.
Congrats, Jim
Congrats, Jim
The V rated tire has a reinforcement that goes from the bead area of the tire up into the sidewall further than the H rated tire, increasing the steering response and allowing less sidewall flex. Also most V rated tires will have a wider belt edge strip (strip of rubber that goes around the tire at the edges of the steel belts) that gives more support to prevent belt edge lift. Also the V rated tire has a heaver nylon cap ply or plies (nylon belts that cover the steel belts). .
Originally Posted By: Tempest
Originally Posted By: CapriRacer
To get a higher speed rating, the tire has to have more cap plies.
S and T rated tires don't need to have a cap ply.
H rated tires need to have one cap ply.
V and higher need to have 2 cap plies.
Notice this does NOT say anything about the sidewall construction.
Slightly
Does this apply to all size tires? Would larger tires require more reinforcement than smaller tires for a given rating?
Yes, it turns out that very large tires - meaning SUV sized - need more reinforcement than smaller (car sized) tires. However, I think you'll find that SUV sized tires come only in S and T ratings, so the point is moot.
Originally Posted By: CapriRacer
To get a higher speed rating, the tire has to have more cap plies.
S and T rated tires don't need to have a cap ply.
H rated tires need to have one cap ply.
V and higher need to have 2 cap plies.
Notice this does NOT say anything about the sidewall construction.
Slightly
Does this apply to all size tires? Would larger tires require more reinforcement than smaller tires for a given rating?
Yes, it turns out that very large tires - meaning SUV sized - need more reinforcement than smaller (car sized) tires. However, I think you'll find that SUV sized tires come only in S and T ratings, so the point is moot.
Originally Posted By: Colt
The V rated tire has a reinforcement that goes from the bead area of the tire up into the sidewall further than the H rated tire, increasing the steering response and allowing less sidewall flex......
Not necessarily. This is the whole point of the discussion. Some higher speed rated tires aren't designed for quick response - they are designed for a better ride. That's the trade-off.
Originally Posted By: Colt
...... Also most V rated tires will have a wider belt edge strip (strip of rubber that goes around the tire at the edges of the steel belts) that gives more support to prevent belt edge lift......
Actually, V rated tires have a pair of cap plies in order to pass the speed rating test.
Having said that, there are some variations on the theme, but 2 cap plies for a V rated tire is a good rule of thumb.
Originally Posted By: Colt
..... Also the V rated tire has a heaver nylon cap ply or plies (nylon belts that cover the steel belts). .
Don't get confused about strips at the edge of the belts and cap plies. In some respects they are the same thing.
The V rated tire has a reinforcement that goes from the bead area of the tire up into the sidewall further than the H rated tire, increasing the steering response and allowing less sidewall flex......
Not necessarily. This is the whole point of the discussion. Some higher speed rated tires aren't designed for quick response - they are designed for a better ride. That's the trade-off.
Originally Posted By: Colt
...... Also most V rated tires will have a wider belt edge strip (strip of rubber that goes around the tire at the edges of the steel belts) that gives more support to prevent belt edge lift......
Actually, V rated tires have a pair of cap plies in order to pass the speed rating test.
Having said that, there are some variations on the theme, but 2 cap plies for a V rated tire is a good rule of thumb.
Originally Posted By: Colt
..... Also the V rated tire has a heaver nylon cap ply or plies (nylon belts that cover the steel belts). .
Don't get confused about strips at the edge of the belts and cap plies. In some respects they are the same thing.
All of the very good tech aside, I have 2 sets of V rated PrimacyMXV4's and both are very good riding tires. One set replaced a set of older Good Year Assurance H rated and the other a set of T rated hydroedge. Both cars ride better than they did on the prior sets.
As an aside the Acura is turning in some of the highest fuel mileage numbers it ever has by a couple of MPG on highway trips.
I think you will be fine on the V rated Primacy's.
As an aside the Acura is turning in some of the highest fuel mileage numbers it ever has by a couple of MPG on highway trips.
I think you will be fine on the V rated Primacy's.
Thanks for the info everyone, having them put on in a couple of hours
Goose
Goose
Originally Posted By: CapriRacer
Originally Posted By: Blue_Goose
Originally Posted By: friendly_jacek
Way too much B.S. in this thread. Speed rating has nothing to do with sidewall stiffens and everything to do with a nylon cap.
Can you explain further? Not being a smarty, just would like to know
Goose
To get a higher speed rating, the tire has to have more cap plies.
S and T rated tires don't need to have a cap ply.
H rated tires need to have one cap ply.
V and higher need to have 2 cap plies.
Notice this does NOT say anything about the sidewall construction.
The quantity of misinformation in this thread is mind-boggling. 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. The rating would be more descriptive if it were called the "guaranteed explosion temperature rating," but that terminology might hurt tire sales.
On each and every rotation of the tire, the sidewall flexes; the tire is "flatter" (smaller distance from the wheel rim to the road) at the bottom and "taller" (greater distance from the rim to the outside of the tread) at the top of the tire, and it goes from taller to flatter and back to taller once each rotation. If the tire is underinflated, or if the vehicle is heavily loaded, the difference between the taller and flatter dimensions is greater than if the tire is overinflated and the vehicle is lightly loaded.
When the tire sidewall flexes, internal friction generates heat; the faster the vehicle is driven, the more rotations the tire makes in a given time period (with less time within rotations to cool down), the faster the tire heats up and the hotter it gets. At some point it will attain its guaranteed explosion temperature. 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. Speed ratings have nothing whatsoever to do with handling. They also have nothing whatsoever to do with lawyers.
Certain methods of construction allow a tire to rotate faster while generating less heat than other methods of construction. 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. 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.
There is no rule -- none -- about the number of cap plies a tire must have for a specific speed rating. None.
Originally Posted By: Blue_Goose
Originally Posted By: friendly_jacek
Way too much B.S. in this thread. Speed rating has nothing to do with sidewall stiffens and everything to do with a nylon cap.
Can you explain further? Not being a smarty, just would like to know
Goose
To get a higher speed rating, the tire has to have more cap plies.
S and T rated tires don't need to have a cap ply.
H rated tires need to have one cap ply.
V and higher need to have 2 cap plies.
Notice this does NOT say anything about the sidewall construction.
The quantity of misinformation in this thread is mind-boggling. 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. The rating would be more descriptive if it were called the "guaranteed explosion temperature rating," but that terminology might hurt tire sales.
On each and every rotation of the tire, the sidewall flexes; the tire is "flatter" (smaller distance from the wheel rim to the road) at the bottom and "taller" (greater distance from the rim to the outside of the tread) at the top of the tire, and it goes from taller to flatter and back to taller once each rotation. If the tire is underinflated, or if the vehicle is heavily loaded, the difference between the taller and flatter dimensions is greater than if the tire is overinflated and the vehicle is lightly loaded.
When the tire sidewall flexes, internal friction generates heat; the faster the vehicle is driven, the more rotations the tire makes in a given time period (with less time within rotations to cool down), the faster the tire heats up and the hotter it gets. At some point it will attain its guaranteed explosion temperature. 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. Speed ratings have nothing whatsoever to do with handling. They also have nothing whatsoever to do with lawyers.
Certain methods of construction allow a tire to rotate faster while generating less heat than other methods of construction. 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. 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.
There is no rule -- none -- about the number of cap plies a tire must have for a specific speed rating. None.
Originally Posted By: GC4lunch
Originally Posted By: CapriRacer
Originally Posted By: Blue_Goose
Originally Posted By: friendly_jacek
Way too much B.S. in this thread. Speed rating has nothing to do with sidewall stiffens and everything to do with a nylon cap.
Can you explain further? Not being a smarty, just would like to know
Goose
To get a higher speed rating, the tire has to have more cap plies.
S and T rated tires don't need to have a cap ply.
H rated tires need to have one cap ply.
V and higher need to have 2 cap plies.
Notice this does NOT say anything about the sidewall construction.
The quantity of misinformation in this thread is mind-boggling. 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. The rating would be more descriptive if it were called the "guaranteed explosion temperature rating," but that terminology might hurt tire sales.
On each and every rotation of the tire, the sidewall flexes; the tire is "flatter" (smaller distance from the wheel rim to the road) at the bottom and "taller" (greater distance from the rim to the outside of the tread) at the top of the tire, and it goes from taller to flatter and back to taller once each rotation. If the tire is underinflated, or if the vehicle is heavily loaded, the difference between the taller and flatter dimensions is greater than if the tire is overinflated and the vehicle is lightly loaded.
When the tire sidewall flexes, internal friction generates heat; the faster the vehicle is driven, the more rotations the tire makes in a given time period (with less time within rotations to cool down), the faster the tire heats up and the hotter it gets. At some point it will attain its guaranteed explosion temperature. 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. Speed ratings have nothing whatsoever to do with handling. They also have nothing whatsoever to do with lawyers.
Certain methods of construction allow a tire to rotate faster while generating less heat than other methods of construction. 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. 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.
There is no rule -- none -- about the number of cap plies a tire must have for a specific speed rating. None.
This is the most "fantastic" explanation about tires. IE: full of fantasia. You better provide your sources!
Originally Posted By: CapriRacer
Originally Posted By: Blue_Goose
Originally Posted By: friendly_jacek
Way too much B.S. in this thread. Speed rating has nothing to do with sidewall stiffens and everything to do with a nylon cap.
Can you explain further? Not being a smarty, just would like to know
Goose
To get a higher speed rating, the tire has to have more cap plies.
S and T rated tires don't need to have a cap ply.
H rated tires need to have one cap ply.
V and higher need to have 2 cap plies.
Notice this does NOT say anything about the sidewall construction.
The quantity of misinformation in this thread is mind-boggling. 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. The rating would be more descriptive if it were called the "guaranteed explosion temperature rating," but that terminology might hurt tire sales.
On each and every rotation of the tire, the sidewall flexes; the tire is "flatter" (smaller distance from the wheel rim to the road) at the bottom and "taller" (greater distance from the rim to the outside of the tread) at the top of the tire, and it goes from taller to flatter and back to taller once each rotation. If the tire is underinflated, or if the vehicle is heavily loaded, the difference between the taller and flatter dimensions is greater than if the tire is overinflated and the vehicle is lightly loaded.
When the tire sidewall flexes, internal friction generates heat; the faster the vehicle is driven, the more rotations the tire makes in a given time period (with less time within rotations to cool down), the faster the tire heats up and the hotter it gets. At some point it will attain its guaranteed explosion temperature. 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. Speed ratings have nothing whatsoever to do with handling. They also have nothing whatsoever to do with lawyers.
Certain methods of construction allow a tire to rotate faster while generating less heat than other methods of construction. 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. 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.
There is no rule -- none -- about the number of cap plies a tire must have for a specific speed rating. None.
This is the most "fantastic" explanation about tires. IE: full of fantasia. You better provide your sources!
Originally Posted By: friendly_jacek
This is the most "fantastic" explanation about tires. IE: full of fantasia. You better provide your sources!
The explanation happens to be true. I have worked as a consultant to firms in the tire industry for four decades. If you want further verification, I suggest that you consult the technical sources to which the NHTSA (National Highway and Traffic Safety Administration of the United States Department of Transportation) adverted in its rulemaking to establish the Uniform Tire Quality Grading (UTQG) standards. For a "light" version, here is a short excerpt from the official comment that Consumers Union (publisher of Consumer Reports) submitted in January 2001 in connection with NHTSA rulemaking concerning proposed amendments to the UTQG: Consumers Union testimony:
Quote:
4) SPEED RATING INFORMATION:
· Speed rating information and UTQG Temperature rating are virtually redundant; both are assigned under a "high speed" test condition. UTQG Temperature grades could potentially be eliminated in lieu of the "speed capacity" information noted above.
This is the most "fantastic" explanation about tires. IE: full of fantasia. You better provide your sources!
The explanation happens to be true. I have worked as a consultant to firms in the tire industry for four decades. If you want further verification, I suggest that you consult the technical sources to which the NHTSA (National Highway and Traffic Safety Administration of the United States Department of Transportation) adverted in its rulemaking to establish the Uniform Tire Quality Grading (UTQG) standards. For a "light" version, here is a short excerpt from the official comment that Consumers Union (publisher of Consumer Reports) submitted in January 2001 in connection with NHTSA rulemaking concerning proposed amendments to the UTQG: Consumers Union testimony:
Quote:
4) SPEED RATING INFORMATION:
· Speed rating information and UTQG Temperature rating are virtually redundant; both are assigned under a "high speed" test condition. UTQG Temperature grades could potentially be eliminated in lieu of the "speed capacity" information noted above.
Lets see, a letter from CR proposing (rejected) changes to tire labeling to make tires easier to read for consumers. I can't see anything that supports your claims.
Can you do better than that? Especially as a tire consultant.
Can you do better than that? Especially as a tire consultant.
Originally Posted By: friendly_jacek
Lets see, a letter from CR proposing (rejected) changes to tire labeling to make tires easier to read for consumers.
Apparently, you did not read it. C'est dommage.
Quote:
I can't see anything that supports your claims.
In the section discussing the UTQG Temperature rating, CU also discusses the European speed rating system, but, then, you would have to have read CU's submission to know that. Try reading before posting.
Quote:
Can you do better than that? Especially as a tire consultant.
Can you cite anything to establish thet ECE-30 (the European speed rating criteria) have ever been about anything other than the ability of a tire to dissipate heat?
Here is a link for the English text of the test procedures that the Economic Commission for Europe (ECE) adopted for the speed rating system. Procedure for Load/Speed Performance Tests Read, mark, learn, and inwardly digest the regulations. [Warning: if you could not comprehend CU's submission to the NHTSA, then you will be thoroughly flummoxed by the ECE regulations. Please do not return, not having read the regs, to exhibit your ignorance.] Get back to us when you determine that there is any criterion to establish a speed rating other than how fast the tire under test can rotate under load before it reaches a critical temperature that leads to a catastrophic failure.
Lets see, a letter from CR proposing (rejected) changes to tire labeling to make tires easier to read for consumers.
Apparently, you did not read it. C'est dommage.
Quote:
I can't see anything that supports your claims.
In the section discussing the UTQG Temperature rating, CU also discusses the European speed rating system, but, then, you would have to have read CU's submission to know that. Try reading before posting.
Quote:
Can you do better than that? Especially as a tire consultant.
Can you cite anything to establish thet ECE-30 (the European speed rating criteria) have ever been about anything other than the ability of a tire to dissipate heat?
Here is a link for the English text of the test procedures that the Economic Commission for Europe (ECE) adopted for the speed rating system. Procedure for Load/Speed Performance Tests Read, mark, learn, and inwardly digest the regulations. [Warning: if you could not comprehend CU's submission to the NHTSA, then you will be thoroughly flummoxed by the ECE regulations. Please do not return, not having read the regs, to exhibit your ignorance.] Get back to us when you determine that there is any criterion to establish a speed rating other than how fast the tire under test can rotate under load before it reaches a critical temperature that leads to a catastrophic failure.
Originally Posted By: GC4lunch
The quantity of misinformation in this thread is mind-boggling. 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. The rating would be more descriptive if it were called the "guaranteed explosion temperature rating," but that terminology might hurt tire sales......
I'm sorry, but that is not correct.
Both the speed rating and the UTQG Temperature ratings are not tied to temperature. 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.
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. Temperature is NOT the criteria used to determine the speed rating.
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.
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.
Originally Posted By: GC4lunch
.......There is no rule -- none -- about the number of cap plies a tire must have for a specific speed rating. None.
You're right. There is no "rule", but 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.
The quantity of misinformation in this thread is mind-boggling. 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. The rating would be more descriptive if it were called the "guaranteed explosion temperature rating," but that terminology might hurt tire sales......
I'm sorry, but that is not correct.
Both the speed rating and the UTQG Temperature ratings are not tied to temperature. 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.
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. Temperature is NOT the criteria used to determine the speed rating.
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.
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.
Originally Posted By: GC4lunch
.......There is no rule -- none -- about the number of cap plies a tire must have for a specific speed rating. None.
You're right. There is no "rule", but 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.
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