Tire Speed Rating Decoder
Decode tire speed rating letters from L to Y, plus ZR and (Y). Get the maximum speed for each rating in km/h, mph and m/s.
Explain speed rating designations.
Tire Speed Rating Decoder: Tire Size Inputs
Compare two tire sizes here. Use the formulas and reference tables below for this tool's specific calculation.
How Tire Speed Rating Decoder Works?
The Tire Speed Rating Decoder works by matching the speed rating letter in the service description to the standard speed category table. The tool uses 3 steps.
Find the letter
Read the letter after the load index, for example W in 94W.
Look up the speed
The decoder returns 270 km/h (168 mph) for W.
Check ZR markings
The decoder explains that ZR inside the size means a rating above 240 km/h (149 mph) and that the service description gives the exact category.
Tire Speed Rating Decoder Formula
The Tire Speed Rating Decoder uses a lookup table with one conversion: mph = km/h ÷ 1.609344.
V_max = Table[letter] (km/h)V_mph = V_kmh ÷ 1.609344V_ms = V_kmh ÷ 3.6- letter
- Speed symbol from L to Y
- V_max
- Maximum sustained speed at rated load
Worked example
A tire marked 98Y is rated for 300 km/h (186 mph). A tire marked 113T is rated for 190 km/h (118 mph).
Tire Speed Rating Decoder Conversion Table
The Tire Speed Rating Decoder conversion table lists 15 speed rating symbols with maximum speed in 3 units.
| Rating | km/h | mph | m/s |
|---|---|---|---|
| L | 120 km/h | 75 mph | 33.3 m/s |
| M | 130 km/h | 81 mph | 36.1 m/s |
| N | 140 km/h | 87 mph | 38.9 m/s |
| P | 150 km/h | 93 mph | 41.7 m/s |
| Q | 160 km/h | 99 mph | 44.4 m/s |
| R | 170 km/h | 106 mph | 47.2 m/s |
| S | 180 km/h | 112 mph | 50.0 m/s |
| T | 190 km/h | 118 mph | 52.8 m/s |
| U | 200 km/h | 124 mph | 55.6 m/s |
| H | 210 km/h | 130 mph | 58.3 m/s |
| V | 240 km/h | 149 mph | 66.7 m/s |
| W | 270 km/h | 168 mph | 75.0 m/s |
| Y | 300 km/h | 186 mph | 83.3 m/s |
| ZR | > 240 km/h | > 149 mph | > 66.7 m/s |
| (Y) | > 300 km/h | > 186 mph | > 83.3 m/s |
What is Tire Speed Rating Decoder?
A Tire Speed Rating Decoder is a tool that translates the speed rating letter on a tire into the maximum speed the tire sustains under rated load. Tire makers test ratings on a laboratory drum in speed steps.
The letters run alphabetically from L to Y, with one exception. H (210 km/h, 130 mph) sits between U and V.
The rating assumes correct pressure, rated load and an undamaged tire. Underinflation, overload, wear and repairs lower the safe speed.
What are the uses of Tire Speed Rating Decoder?
There are 4 main uses of the Tire Speed Rating Decoder, including replacement matching and winter tire rules.
Replacement matching
Match or exceed the original speed rating.
Winter tire rules
Check the lower rating of a winter tire against regional rules.
Track day prep
Confirm the rating suits the speeds reached on track.
Import checks
Read ratings on tires bought from another market.
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