Tire speed rating chart and check

Speed rating chart

Speeds in km/h come from Continental's chart [Continental speed chart]. Miles per hour are km/h ÷ 1.609344, rounded to the nearest whole number, which gives every mph figure in Continental's chart except Z's (see below) and every figure in Bridgestone's list [Bridgestone tire size].

Z, (W) and (Y) are open-ended: they say a tire is rated above a speed, not up to it. Z and (W) are rows of Continental's chart (it rounds Z to above 150 mph; 240 km/h is 149.1 mph). (Y) comes from Continental's text:

“UHP tires usually carry W, Y, or (Y) symbols (168 mph / 270 km/h to 186 mph / 300 km/h or more).” [Continental speed chart]

“(Y) or similar indications can imply even higher capabilities, but these are special cases requiring manufacturer testing.” [Continental speed chart]

So for a tire marked (Y), or with the whole service description in parentheses such as (97Y), only the tire maker can give its top speed.

The letters mostly run in alphabetical order. The exception is H:

“Instead of appearing after “G,” it falls between “U” and “V” as does the speed to which it corresponds.” [Bridgestone speed rating]

Replacing a tire: the same rating or higher

Two tire makers state the rule for replacement tires:

“Replacement tires must have the same or higher speed rating to maintain vehicle speed capability. If a vehicle has tires with different speed ratings, the speed rating of the "slowest" tire dictates the vehicle’s top speed.” [Bridgestone tire size]

“Replacement tires should always meet or exceed the speed rating specified by the vehicle manufacturer.” [Michelin load and speed]

Michelin allows one exception, for tires built for snow:

“Using tires with a lower speed rating is not recommended unless the tires are winter-capable, such as Winter or All-Season tires marked with the 3-Peak Mountain Snowflake (3PMSF) symbol. In these cases, drivers must ensure the vehicle is not operated above the tire’s maximum rated speed.” [Michelin load and speed]

Worked example

Your vehicle came on 225/65R17 102H, and a shop offers a used 225/65R17 102T. The sizes and load indexes match, but the speed ratings do not: T is up to 118 mph (190 km/h) and H up to 130 mph (210 km/h), so the used tire is rated 12 mph (20 km/h) lower. By Bridgestone's rule it is not a like-for-like replacement; Michelin allows it only on a winter-capable tire, and then the vehicle must not be driven faster than the tire's own rated speed. Either way, on a vehicle with mixed ratings the T tire sets the top speed.

Mixed ratings: the slowest tire sets the top speed

Buying one or two used tires often leaves a vehicle with tires of different ratings. Bridgestone's rule, quoted above, is that the “slowest” tire then dictates the vehicle's top speed. Type the letters of the tires staying on the vehicle in the check (for example H H T) and it names the slowest rating on the vehicle and compares it with the original. An open-ended symbol counts at the speed it is rated above, so the answer is never faster than the slowest tire can be.

Z and ZR in the size

“Some manufacturers will insert a “Z” in the middle of the tire size description (right after the aspect ratio) when the tire is rated at “W” or “Y.”” [Bridgestone speed rating]

“Historically, the letter Z was introduced to show that a tire could safely handle speeds above approximately 240 km/h (149 mph), but it did not specify a precise top limit on its own.” [Continental speed chart]

So for a size such as 225/45ZR17 94W, read the rating from the letter after the load index (W, up to 168 mph). A ZR size with no service description is rated above 240 km/h (149 mph), and one marked in parentheses, such as 255/35ZR20 (97Y), is rated above the letter's speed: for both, ask the tire maker for the top speed.

What a speed rating does not promise

“Speed ratings do not apply to tires that have been damaged, altered, under-inflated, overloaded or repaired.” [Bridgestone speed rating]

“Speed ratings are based on laboratory tests that relate to performance on the road, but are not applicable if tires are underinflated, overloaded, worn out, damaged, or altered.” [Mastercraft]

“It is risky to assume a tire rated for 210 km/h or 130 mph (H) is always safe at that speed regardless of other factors.” [Continental speed chart]

On a used tire, that makes the other checks part of the speed question too: the date code, the tread depth, any repairs, and the load index against what your vehicle needs.