Understanding Speed Ratings

Wednesday, December 1, 2010 by Gary Stanley

Ever wonder what the letter in your tire size means?  For example, the "Z" in 245/45ZR17 or the  "H" in 205/55R16 89H.  This letter is the speed rating of the tire. 

Tires are tested in laboratory conditions under load by tire manufacturers to determine the maximum speed capability of the tire. 

Shown below is what the speed rating letter equates to in MPH. 
 

  L 75 mph 120 km/h Off-Road & Light Truck Tires
  M 81 mph 130 km/h  
  N 87 mph 140km/h Temporary Spare Tires
  P 93 mph 150 km/h  
  Q 99 mph 160 km/h Studless & Studdable Winter Tires
  R 106 mph 170 km/h H.D. Light Truck Tires
  S 112 mph 180 km/h Family Sedans & Vans
  T 118 mph 190 km/h Family Sedans & Vans
  U 124 mph 200 km/h  
  H 130 mph 210 km/h Sport Sedans & Coupes
  V 149 mph 240 km/h Sport Sedans, Coupes & Sports Cars
  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.

You can learn more about speed rating and the other letters and numbers on the sidewall of your tire in "How to Read Speed Rating, Load Index & Service Descriptions." 

Disclaimer: It is important to note that speed ratings only apply to tires that have not been damaged, altered, underinflated or overloaded. Additionally, most tire manufacturers maintain that a tire that has been cut or punctured no longer retains the tire manufacturer's original speed rating.

Comments on Understanding Speed Ratings

Tuesday, January 31, 2012 by Myron:
what tire is best for bonneville salt flats, 210 mph on a 2012 susuki hayabusa
Thursday, November 1, 2012 by jon:
can I ignore speed rating requirements for winter tires
Thursday, November 1, 2012 by Gary:
Jon,

Most vehicle manufacturers do not insist that you maintain the original tire speed rating when installing winter tires.
Monday, November 5, 2012 by Larry:
Hi, I am looking at purchasing a set of used 205/60/16 92Q Bridgestone Blizzak winter tires for a mazda 6s wagon. Are these tires acceptable for us on my car?
Thursday, November 15, 2012 by Shelley:
I have a speed rating of 93V on my car. Is it necessary to replace the tires with the same speed rating or can it be changed?
Thursday, November 15, 2012 by Gary:
Shelley,

What is the year and model of the vehicle?
Thursday, November 15, 2012 by Gary:
Larry,

Yes, for winter tires it is acceptable to use a lower than factory speed rating.
Monday, December 17, 2012 by George:
What is the difference between 89H vs 91H. What will happen if you have one of each on the front of a front wheel drive vehicle (2010 VW Jetta SE)
Monday, December 17, 2012 by Gary:
A 91H tire has a load capacity of 1356lbs per tire compared to 1279lbs per tire on an 89H. It is not recommended to mix different ratings on the same axle of a vehicle.
Tuesday, December 25, 2012 by bill:
i have a subaru BAJA wich i drive threw fields. i cant find a agressive tire for it. so some one recomended going up 1 size to a 235-60-16. but the speed tating ist the same. how important is that. some tire installers wont install on my car/truck but why do i need a V rated tire. i wont be going 118 mph. i wanted the BFG rugged terrain. do you think this would be ok?
Tuesday, June 18, 2013 by Dick:
Is it OK to go from a H rating to a T rating on my RAV-4 new tires?
Monday, June 24, 2013 by Gary:
Dick,

As long as all four tires are matching, highly rated, quality tires then the answer is generally yes. Keep in mind that the speed rating of a tire is not a measure of the tires grip or handling, but is a a rated result of a test for maximum sustained speed capability of the tire. Refer to the chart in my blog to be sure that you aren't exceeding the speed capability of the tire you are considering.

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