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TIRE SPEED RATING & TREAD LIFE

Speed ratings are not just about speed. They correlate directly with ride comfort, treadwear, and cornering ability. Typically the higher the speed rating, the better the grip and stopping power, but the shorter the tread life. Ratings run from A at the lowest to Y at the highest, and the chart is not strictly alphabetical: H sits between U and V, a holdover from when H stood for high performance.
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THE ORIGIN OF SPEED RATINGS

We can thank Germany’s famous Autobahn for tire speed ratings. Tire speed ratings range from A (the lowest) to Y (the highest). But the chart is not completely in alphabetical order. For example, H is between U and V, with the common perception that H stood for “high performance” at one time.

As manufacturers continue to add speed to their vehicles, tire speed ratings evolve to match the speeds. For example, Z was the highest rated speed at 240 kph + until W & Y were used to match the higher speeds of exotic sports cars.

SPEED RATINGS REFER TO MORE THAN JUST SPEED

Contrary to the name, speed ratings aren’t just about speed. They’re also about ride comfort, wear and cornering ability. Typically, the higher the speed rating, the better the grip and stopping power, but the lower the tread life. You can always increase the speed rating of the tires on your vehicle for improved performance, but can never decrease it without reducing the vehicle top speed to that of the lower speed rating selected.

MIXING SPEED RATINGS

We certainly don’t recommend it, but if tires of different speed ratings are mounted on a vehicle, the lower speed-rated tires should be placed on the front axle regardless of which axle is driven. This is to prevent a potential oversteer condition. Vehicle handling may be affected, and the vehicle’s speed capacity is now limited to the lowest speed-rated tire. For best performance, it is recommended that the same size and type of tire be used on all four wheel positions.

LOAD INDEX

235/55R17 99H- The load index (99) is the tire size's assigned numerical value used to compare relative load carrying capabilities. The higher the tire's load index number, the greater its load carrying capacity.

  • 97 = 730 kg (1,609 pounds)

  • 98 = 750 kg (1,653 pounds)

  • 99 = 775 kg (1,709 pounds)

A tire with a higher load index than that of the Original Equipment tire indicates an increase in load capacity. A tire with a load index equal to that of the Original Equipment tire indicates an equivalent load capacity. A tire with a lower load index than the Original Equipment tire indicates the tire does not equal the load capacity of the original and should not be considered for installation on the vehicle.

Typically, the load indexes of the tires used on passenger cars and light trucks range from 70 to 130.

Frequently asked questions

BFGoodrich answers your most asked questions.

FAQ

S is rated to 180 km/h, T to 190, H to 210, V to 240, W to 270, and Y to 300. Z was once the top of the scale at 240 and above, until W and Y were introduced to match the speeds of exotic sports cars. The rating certifies the maximum speed the tire can carry its rated load under specified conditions.

S is rated to 180 km/h. It is common on winter tires, touring tires, and many light truck and SUV fitments where outright speed capability is less important than tread life and ride comfort. If your vehicle came with a higher rating, fitting S-rated tires reduces your vehicle's rated top speed accordingly.

The chart is not in strict alphabetical order because of how it developed historically. H was introduced separately with the common perception that it stood for high performance, and it kept that position when the rest of the scale was standardized. This is why you cannot assume a later letter always means a higher rating.

Yes, and many Canadian drivers do. Winter tires are often available in lower speed ratings than the summer set. Doing so is acceptable, but it reduces your vehicle's safe top speed to that of the winter tire for as long as they are fitted. Know the number and drive within it.

Usually yes. Higher speed ratings typically use softer compounds and stiffer construction to deliver better grip and shorter stopping distances, and those same properties reduce tread life. A touring tire rated T or H will generally outlast a W or Y rated performance tire on the same vehicle and driving pattern.

Find the load index in your tire's service description, the number just before the speed rating letter. Look it up on a standard load index chart to get the maximum weight that single tire can carry, expressed in kilograms or pounds. Confirm the result meets or exceeds what your vehicle placard requires.

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