why whine about tire rating?
08-09-2005, 03:09 PM
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why whine about tire rating? I did a search on the Pirelli p zero nero m+s tire, from the ratings on tire rack and everything, its a great tire. i got the W rated. in the search, regrading tires in general i would read, "yea but its w rated". did i screw myself? becuase i was thinking about how W rated tired are good for heat till 168 miles per hour....ok so who the hell goes abour 170 miles per hour in their car?? ....if youre running that at the track, its not on street tires, Z rated -149+ - anyways.
08-09-2005, 03:53 PM
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btw, the speed rating is based on tire temps over a period of 1 hour.
W rated are good for straight running at 168 for 1 hour.
You can do 200mph on a W rated tire for a short period but you risk blowing out the tire due to excessive heat.
W rated are good for straight running at 168 for 1 hour.
You can do 200mph on a W rated tire for a short period but you risk blowing out the tire due to excessive heat.
08-09-2005, 09:44 PM
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so why do people spend money on Z rated tires if theyre not at the speedways running laps for an hour? I mean like i asked, did i screw myself. since i owned the car ive had 2 or 3 sets all z rated, my dad said eh save some money buy the pirellis i just got, but theyre W rated even though they're great. im kinda thinkin like man i got a worse tire, but then im say wait, im not going over 149 miles an hour. the fastest ive had it since i owned it was 135 for like 10 second
08-09-2005, 10:07 PM
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From, Tire Racks tech section
http://www.tirerack.com/tires/tirete....jsp?techid=35
When Z-speed rated tires were first introduced, they were thought to reflect the highest tire speed rating that would ever be required, in excess of 240 km/h or 149 mph. While Z-speed rated tires are capable of speeds in excess of 149 mph, how far above 149 mph was not identified. That ultimately caused the automotive industry to add W- and Y-speed ratings to identify the tires that meet the needs of new vehicles that have extremely high top-speed capabilities.
W 168 mph 270 km/h Exotic Sports Cars
Y 186 mph 300 km/h Exotic Sports Cars
While a Z-speed rating still often appears in the tire size designation of these tires, such as 225/50ZR16 91W, the Z in the size signifies a maximum speed capability in excess of 149 mph, 240 km/h; the W in the service description indicates the tire's 168 mph, 270 km/h maximum speed.
225/50ZR16 in excess of 149 mph, 240 km/h
205/45ZR17 88W 168 mph, 270 km/h
285/35ZR19 99Y 186 mph, 300 km/h
Most recently, when the Y-speed rating indicated in a service description is enclosed in parentheses, such as 285/35ZR19 (99Y), the top speed of the tire has been tested in excess of 186 mph, 300 km/h indicated by the service description as shown below:
285/35ZR19 99Y 186 mph, 300 km/h
285/35ZR19 (99Y) in excess of 186 mph, 300 km/h
As vehicles have increased their top speeds into Autobahn-only ranges, the tire speed ratings have evolved to better identify the tires capability, allowing drivers to match the speed of their tires with the top speed of their vehicle.
http://www.tirerack.com/tires/tirete....jsp?techid=35
When Z-speed rated tires were first introduced, they were thought to reflect the highest tire speed rating that would ever be required, in excess of 240 km/h or 149 mph. While Z-speed rated tires are capable of speeds in excess of 149 mph, how far above 149 mph was not identified. That ultimately caused the automotive industry to add W- and Y-speed ratings to identify the tires that meet the needs of new vehicles that have extremely high top-speed capabilities.
W 168 mph 270 km/h Exotic Sports Cars
Y 186 mph 300 km/h Exotic Sports Cars
While a Z-speed rating still often appears in the tire size designation of these tires, such as 225/50ZR16 91W, the Z in the size signifies a maximum speed capability in excess of 149 mph, 240 km/h; the W in the service description indicates the tire's 168 mph, 270 km/h maximum speed.
225/50ZR16 in excess of 149 mph, 240 km/h
205/45ZR17 88W 168 mph, 270 km/h
285/35ZR19 99Y 186 mph, 300 km/h
Most recently, when the Y-speed rating indicated in a service description is enclosed in parentheses, such as 285/35ZR19 (99Y), the top speed of the tire has been tested in excess of 186 mph, 300 km/h indicated by the service description as shown below:
285/35ZR19 99Y 186 mph, 300 km/h
285/35ZR19 (99Y) in excess of 186 mph, 300 km/h
As vehicles have increased their top speeds into Autobahn-only ranges, the tire speed ratings have evolved to better identify the tires capability, allowing drivers to match the speed of their tires with the top speed of their vehicle.
08-09-2005, 10:13 PM
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Here is some good info as well,
The speed rating of an automobile tire, sometimes referred to as the speed rating index, is an alphabetic indicator of the maximum vehicle speed for which the tire manufacturer has designed a tire. The overall speed rating system for all vehicles sets forth speed ratings from B (31 mph) to Z (over 150 mph). Passenger car tire speed ratings generally range from S to Z within that system and are set forth in the accompanying speed symbol chart. The speed rating usually appears at the end of the letters and numbers indicating the tire size on the tire sidewall. For example, P275/40R17 93H denotes a tire rated for speeds up to 130 mph, and P275/40ZR17 93V signifies a tire rated for up to 150 mph. There are some intermediate and secondary speed notations in use by some manufacturers, but they are beyond the scope of this article.
Speed ratings are developed using standardized indoor wheel tests similar to those used by NHTSA for temperature ratings. In the case of speed ratings, the tire is subjected to an indoor wheel test prescribed by the Procedure for Load/Speed Performance Tests of the Economic Commission for Europe (ECE-30). The properly inflated tire is subjected to the load for which it is rated (see below) and run on a 1.7 meter wheel. (See the accompanying picture, which shows a tire being tested.) A tire must survive at least 30 minutes at speed to earn the commensurate speed rating.
Remember that a speed rating is the speed at which a tire design has been rated for thirty minutes of running at that speed. Good tire design does not repeal the Law of Physics—running a set of tires at or above its rated speed for a long time courts tire failure and invites a fatal accident. You are more likely to stay out of trouble if you buy tires that have speed ratings that exceed the demands of your driving habits. Replacement tires should have the same or higher load and speed ratings as the original equipment tires specified by the vehicle’s manufacturer.
Maintaining the correct tire pressure is important, since a tire’s speed rating is valid only when it is properly inflated. Underinflation causes heat buildup, the enemy of tires. Repairs affect a tire’s speed rating since any tire’s stated speed rating is invalidated by any repair. According to tire manufacturers, the maximum speed for an otherwise speed-rated tire after it has been repaired is no more than an unrated tire, that is, 85 miles per hour.
Now let’s look at what is meant by the load rating of a tire, later known as its load index. You will recall from my previous article that the Alpha-Numeric tire sizing system uses an alphabetic "load rating" scheme. The use of load ratings on Alpha-Numeric tires replaces the previous Numeric method where the number of plys a tire has is an indicator of how much weight it can handle. In the Alpha-Numeric load index system, the load for an alpha size is the same regardless of rim diameter or aspect ratio. For example, sizes F70-15, F78-14, and FR60-13 all have a maximum load of 1500 pounds when inflated to 32 psi. Generally the manufacturer of an automobile will specify a tire load rating for the tires to be used on the car.
The load index for tires using the later Metric tire sizing system is a numeric indicator, which can be found on a tire’s sidewall following the size description and just in front of the speed rating of the tire. Though the overall system contemplates load indices from 65 (639 pounds) to 104 (1984 pounds), passenger car load ratings range generally from 75 (852 pounds) to 100 (1764 pounds). Therefore a tire marked 205/60R15 89H is rated to carry 1279 pounds (denoted by the 89) and speed rated at 130 mph (denoted by the H). Remember that all tire load ratings are valid only when the tire is fully inflated to the recommended pressure. As we have seen, underinflated tires generate destructive heat that leads to tire failure.
Factors other than those discussed above have a detrimental effect on a tire’s originally specified speed and load ratings. Exposure to sunlight and ozone breaks down the chemical composition of tires, as does grease and gasoline. Tires exposed to these materials during driving and storage may be weakened and subject to sudden failure, regardless of their original speed and load designation. When tires are stored, they should be stored in a cool, dry place away from these materials. Be sure to allow air to circulate around all side of the tires, including underneath, to prevent moisture damage. Don’t store tires on black asphalt, other heat-absorbing surfaces, snow-covered ground, or sand.
The material for this series of tire articles was drawn from many sources, most of which are to be found on the World Wide Web. I particularly want to thank Joe Pacuit of the Tire and Rim Association for his assistance in obtaining some hard to get information.
The speed rating of an automobile tire, sometimes referred to as the speed rating index, is an alphabetic indicator of the maximum vehicle speed for which the tire manufacturer has designed a tire. The overall speed rating system for all vehicles sets forth speed ratings from B (31 mph) to Z (over 150 mph). Passenger car tire speed ratings generally range from S to Z within that system and are set forth in the accompanying speed symbol chart. The speed rating usually appears at the end of the letters and numbers indicating the tire size on the tire sidewall. For example, P275/40R17 93H denotes a tire rated for speeds up to 130 mph, and P275/40ZR17 93V signifies a tire rated for up to 150 mph. There are some intermediate and secondary speed notations in use by some manufacturers, but they are beyond the scope of this article.
Speed ratings are developed using standardized indoor wheel tests similar to those used by NHTSA for temperature ratings. In the case of speed ratings, the tire is subjected to an indoor wheel test prescribed by the Procedure for Load/Speed Performance Tests of the Economic Commission for Europe (ECE-30). The properly inflated tire is subjected to the load for which it is rated (see below) and run on a 1.7 meter wheel. (See the accompanying picture, which shows a tire being tested.) A tire must survive at least 30 minutes at speed to earn the commensurate speed rating.
Remember that a speed rating is the speed at which a tire design has been rated for thirty minutes of running at that speed. Good tire design does not repeal the Law of Physics—running a set of tires at or above its rated speed for a long time courts tire failure and invites a fatal accident. You are more likely to stay out of trouble if you buy tires that have speed ratings that exceed the demands of your driving habits. Replacement tires should have the same or higher load and speed ratings as the original equipment tires specified by the vehicle’s manufacturer.
Maintaining the correct tire pressure is important, since a tire’s speed rating is valid only when it is properly inflated. Underinflation causes heat buildup, the enemy of tires. Repairs affect a tire’s speed rating since any tire’s stated speed rating is invalidated by any repair. According to tire manufacturers, the maximum speed for an otherwise speed-rated tire after it has been repaired is no more than an unrated tire, that is, 85 miles per hour.
Now let’s look at what is meant by the load rating of a tire, later known as its load index. You will recall from my previous article that the Alpha-Numeric tire sizing system uses an alphabetic "load rating" scheme. The use of load ratings on Alpha-Numeric tires replaces the previous Numeric method where the number of plys a tire has is an indicator of how much weight it can handle. In the Alpha-Numeric load index system, the load for an alpha size is the same regardless of rim diameter or aspect ratio. For example, sizes F70-15, F78-14, and FR60-13 all have a maximum load of 1500 pounds when inflated to 32 psi. Generally the manufacturer of an automobile will specify a tire load rating for the tires to be used on the car.
The load index for tires using the later Metric tire sizing system is a numeric indicator, which can be found on a tire’s sidewall following the size description and just in front of the speed rating of the tire. Though the overall system contemplates load indices from 65 (639 pounds) to 104 (1984 pounds), passenger car load ratings range generally from 75 (852 pounds) to 100 (1764 pounds). Therefore a tire marked 205/60R15 89H is rated to carry 1279 pounds (denoted by the 89) and speed rated at 130 mph (denoted by the H). Remember that all tire load ratings are valid only when the tire is fully inflated to the recommended pressure. As we have seen, underinflated tires generate destructive heat that leads to tire failure.
Factors other than those discussed above have a detrimental effect on a tire’s originally specified speed and load ratings. Exposure to sunlight and ozone breaks down the chemical composition of tires, as does grease and gasoline. Tires exposed to these materials during driving and storage may be weakened and subject to sudden failure, regardless of their original speed and load designation. When tires are stored, they should be stored in a cool, dry place away from these materials. Be sure to allow air to circulate around all side of the tires, including underneath, to prevent moisture damage. Don’t store tires on black asphalt, other heat-absorbing surfaces, snow-covered ground, or sand.
The material for this series of tire articles was drawn from many sources, most of which are to be found on the World Wide Web. I particularly want to thank Joe Pacuit of the Tire and Rim Association for his assistance in obtaining some hard to get information.