To get the best use out of your car, it is crucial that you understand its functions and mechanisms. Therefore, in today’s guidelines, let’s have a look at tire speed rating and the impact it exerts on the vehicle. Learn more about the definition of this concept and how to read tire speed rating right away!
What Is Tire Speed Rating?
The tire speed rating refers to the tire’s capability to go at the highest speed for an extended amount of time, given favorable circumstances. Simply put, it indicates the optimal performance of a tire before it becomes rundown. Having a high tire speed rating is what all drivers aim at. It would provide them with the power to control acceleration effectively.
In an attempt to measure the tire in standardized terms, the speed rating system was introduced. By certifying each tire’s speed rating based on a series of letters and numbers, car manufacturers allow customers to examine the car’s prowess before making the final decision. For example, the lowest rating is 3mph, illustrated as A1. On the other hand, the highest one can reach above 186mph and comes in (Y).
However, you should not be mistaken about the actual ability of a tire and its certification. Even if a tire is labeled as A1, it can still exceed the limit. The only difference is that once it surpasses that threshold, the drive quality and safety would be compromised. The approved rating merely shows the ideal speed for the best ride comfort that drivers should comply with.
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How To Read Tire Speed Rating
How is tire speed rating established?
The tire is subject to a testing machine before the final verdict is out. They may go through two procedures: the ECE (Economic Commission for Europe) and SAE (Society of Automotive Engineers) standardized tests.
Regarding ECE, a tire is blown into its full shape, effectively covering a wheel heated to 77 degrees Fahrenheit or 25 degrees Celsius. A metal drum will mimic the road pressure, simulating how the tire is expected to perform. Then, engineers would give out an ideal rating and lower it by 40km/h (the test is tailored based on the European scale). Next, the tire starts spinning for 10 minutes straight and gradually picks up its speed until it reaches the goal.
While at the suggested rating, the tire continues to spin for another 10 minutes before being taken down for inspection. If the tire remains intact and there are no signs of wear and tear, or broken tread components, it passes the test. For extra cautions, a step-up speed test is sometimes included in the process. Here, the tire keeps on spinning at increased speeds until it falls. This way, manufacturers can advise customers to stay under a certain speed limit for total safety.
Regarding SAE, all the steps are pretty much the same. But the conditions required are different. Instead of spinning for 10 minutes once reaching the target speed, the tire has to spin for an hour. As far as the temperature is concerned, the room is heated at 100 degrees Fahrenheit or 37.77 degrees Celsius.
Why is tire speed rating developed?
The history of tire speed rating goes back to the 1960s when there was no framework to evaluate tire performance at different speeds. As a result, manufacturers introduced a system that collects data regarding the maximal speed of tires in ideal conditions. The system soon became widely popular and was adopted globally. Adjustments and modifications to include all speed classes were made gradually until the final rating chart was publicized.
What are the different speed ratings?
Speed ratings vary significantly from one car type to another. In most cases, the higher the speed rating is, the later it sits in the chart. By that logic, tires labeled as P definitely work better than those labeled as E.
As the speed limits are usually 75mp (an equivalent of L-rated tires), most drivers would choose to stay within the safe lane. For cars used for commuting or family purposes, S-rated or T-rated tires would suffice. These include light trucks, minivans, or sedans. Sports car enthusiasts driving coupes may enjoy H-rated tires, and so do medium vans drivers. If you happen to own a high-performance car, be on the outlook for tires rated at least V and above. Finally, there are winter tires labeled as Q, S, and T for the best grip on the road, especially when the surface is unstable and slippery.
What is the tire load index?
If tire speed rating is all about how fast your tires can move, then tire load index measures the weight your tires can carry. The higher it is, the heavier the tire can support for a sustained period in its top conditions. For example, 52 means the tire is capable of moving even while there are 441 lbs on top. At the same time, tires bearing at most 2679 lbs would have a 115 load index. Multiplying this number by four (or more, depending on how many tires your vehicle has), and you know how much your car can load. Typically, a sedan’s tire has a load index anywhere from 70 to 100.
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Tire Speed Rating Chart
A standard speed rating chart is used for cars universally to better understand the previously mentioned theoretical knowledge. Most of the letters are arranged alphabetically, except for H. H, S, and V were the only three letters first used in European tire speed ratings back in the 20th century. As time went by, tire performance was significantly improved, and the original ratings were expanded further. As a result, other letters started to fill in the chart, but H still remains where it was intended in the first place. Thus, it now sits between U and V instead of G and J.
Another detail to pay attention to when looking at the tire speed rating chart is the ZR combination. Sometimes, it may appear on tires capable of hitting above 149mph, alongside letters W and Y. If the tire is marked as (Y), indicating at least 186mph in the driving ability, then ZR must be included.
| Letters | Speed (mph) | Speed (km/h) |
| A1 | 5 | 3 |
| A2 | 10 | 6 |
| A3 | 15 | 9 |
| A4 | 20 | 12 |
| A5 | 25 | 16 |
| A6 | 30 | 19 |
| A8 | 40 | 25 |
| B | 50 | 31 |
| C | 60 | 37 |
| D | 65 | 40 |
| E | 70 | 43 |
| F | 80 | 50 |
| G | 90 | 56 |
| J | 100 | 62 |
| K | 110 | 68 |
| L | 120 | 75 |
| M | 130 | 81 |
| N | 140 | 87 |
| P | 150 | 94 |
| Q | 160 | 100 |
| R | 170 | 106 |
| S | 180 | 112 |
| T | 190 | 118 |
| U | 200 | 124 |
| H | 210 | 130 |
| V | 240 | 149 |
| W | 270 | 168 |
| Y | 300 | 186 |
| (Y) | >300 | >186 |
Conclusion
After reading this detailed article, you definitely know how to read tire speed ratings and understand their implications. So make sure to check out this number next time you want to examine your car so that you can always enjoy the best ride comfort!
