Sometimes letters “ZR” are written in size of tire, is usually mentioned on its sidewall. It is a designation of tire shape and its speed rating.
ZR on a tire basically means that tire has ability to provide good traction at speeds higher than 149 mph or 240 kph.
Table of Contents
What is speed rating?
The speed rating of tire is the code used to define the maximum speeds at which that tire can perform well.
This code consists of one or two letters and there are speed ratings from A to Z, defining different speed ranges for tires.
It is a universal system and all manufacturers use the same codes for the same speed ability.
What is ZR?
ZR is the speed rating for highest speeds as it is used for any tire which has the ability to move with speeds above 149 mph.
Z here actually refers to the speed and R simply indicates that tire is radial.
This speed designation was widely used before 90’s but it is now pretty old-school as speeds higher than 149 mph are now symbolized with V, W and Y. However, you may still find this on some tires.
If a tire size is written as 235/65ZR18, it means this tire can be used for fast driving even above the speed of 149 miles per hour.
But if it is 235/65ZR18 88W, it means that you can drive up to the maximum speed of 168 miles per hour.
As the speed rating shows, ZR tires are high performance tires usually meant of sport purposes.
Usually these tires are built for rims of 17 inch or higher, that is why most are low-profile and have a small sidewall width.
Similarly, the tread rubber of these tires is often softer than tires with lower speed ratings.
This is because softer rubber offers more grip which is necessary to maintain traction at high speed.
| Speed | Miles per hour (mph) | Kilometers per hour (km/h) |
| ZR | 149+ | 240+ |
| V | 149 | 240 |
| W | 168 | 270 |
| Y | 186 | 300 |
Difference between ZR tires and R tires
R in the tire size represents that the tire is radial (its tread has been constructed with radial ply arrangement).
All modern tires are constructed radially except a few ones that are made for antique cars.
Z in ZR specifies higher speed permittivity and R is for radial. So, as ZR actually represents radial tires that allow high speed driving, there is no difference between ZR tires and high speed R tires.
Can I use ZR tires instead of R
Yes, ZR simply means high speed radial tires.
So, these are equivalent to R tires having V, W or Y speed ratings.
If you drive performance vehicles and want tires that provide optimum traction at high speeds, you can use ZR tires instead of R ones on your car without any concern.
Are ZR tires run-flat
Many run-flat tires are ZR rated which means these tires can roll proficiently at higher speeds and can travel to some distance after getting punctured.
As ZR tires are performance tires and run flat feature can prevent huge loss if the tire gets punctured when you are driving at very high speed.
But ZR designation and run-flat ability are not necessarily associated as there are many non-ZR run flat tires available in the market.
Likewise, many ZR tires do not have run flat feature.
Nonetheless, tires which are both ZR and run flat have “ZRF” designation on their sidewalls.
Speed rating chart
A universal speed rating chart is used in tire industry to represent upper speed limits for tires.
The ratings start at A (for lowest speeds) and go up to Y (for highest speeds).
The symbol Z or ZR are synonymous and are used for speed limits above 149.
| Miles per hour (mph) | Kilometers per hour (km/h) | |
| A1 | 3 | 5 |
| A2 | 6 | 10 |
| A3 | 9 | 15 |
| A4 | 12 | 20 |
| A5 | 16 | 25 |
| A6 | 19 | 30 |
| A8 | 25 | 40 |
| B | 31 | 50 |
| C | 37 | 60 |
| D | 40 | 65 |
| E | 43 | 70 |
| F | 50 | 80 |
| G | 56 | 90 |
| J | 62 | 100 |
| K | 68 | 110 |
| L | 75 | 120 |
| M | 81 | 130 |
| N | 87 | 140 |
| P | 94 | 150 |
| Q | 100 | 160 |
| R | 106 | 170 |
| S | 112 | 180 |
| T | 118 | 190 |
| U | 124 | 200 |
| H | 130 | 210 |
| V | 149 | 240 |
| W | 168 | 270 |
| Y | 186 | 300 |
