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 149+ 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 = 1,609 pounds
98 = 1,653 pounds
99 = 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.
Typically, the load indexes of the tires used on passenger cars and light trucks range from 70 to 110.
Frequently asked questions
BFGoodrich answers your most asked questions.
FAQ
S is rated to 112 mph, T to 118, H to 130, V to 149, W to 168, and Y to 186. Z was once the highest at 149 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, not a recommendation to drive there.
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 at one time, and it kept its position when the rest of the scale was standardized. This is why you cannot assume a later letter always means a higher rating.
You can, but it reduces your vehicle's safe top speed to that of the lower-rated tire. Fit a T-rated tire on a vehicle originally equipped with V-rated tires and your maximum safe speed becomes 118 mph, not 149. Many drivers accept this trade deliberately when fitting winter tires, which is fine as long as you know the limit.
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.
Load range E is a load capacity designation common on light truck tires, corresponding to a higher ply rating and higher maximum inflation pressure than load range C or D. It typically appears on tires for heavy-duty pickups, tow rigs, and off-road builds carrying significant weight. Confirm your vehicle placard requirement before choosing a load range.
Find the load index in your tire's service description, the number immediately before the speed rating letter. Look it up on a standard load index chart to get the maximum weight in pounds that single tire can carry. Confirm the result meets or exceeds what your vehicle placard requires.
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