If you have a vehicle with a high-speed capability, you’re more likely to see ZR at the tire size instead of R. Well, ZR indicates the high-speed capability of your tire. ZR basically means your tire is adapted for above 149 mph/h speed.
Normally, tire size(how to read it?) contains the R letter to indicate tire structure. Well, seeing ZR instead of R might make you feel ZR means another construction type. Well, this is totally wrong. ZR tires also have radial construction.
So, where did this ZR come from? Let’s dig into it!
Where did ZR Come From?
Before the ’90s, the tire speed index wasn’t invented. So, the manufacturer was using the ZR letters to define the tires with high-speed capability. For these times, there were no tire catalogs. So, ZR was the indicator of high-performance tires.
Since speed index charts have been released, the ZR letters aren’t relevant to speed rating anymore. However, some manufacturers are still using it due to satisfy the old habits of customers.
What is a Speed Index?
The speed index indicates the maximum velocity capability of the tire. It’s generally equal to the maximum speed of your vehicle.
Since the maximum speed capability of the vehicles mostly isn’t reachable, you may use the tires with a lower speed index. However, in this case, if you’ll pass over the speed index of the tire, your tire will overheat and that might cause lethal accidents. Hence, I recommend buying tires to match the maximum speed capability of your vehicle.
The speed index is indicated with a letter. This letter corresponds to the maximum speed that your tire can make. You can find the conversion table above.
What Speed Indexes do ZR Tires Can Have?
Since ZR tires state the high-speed capability, they can only have the last 4 rows of the speed index chart.
So, basically, ZR tires are subdivided into 4 different labels.
Z – Maximum Speed of 149+ mph/h
W – Maximum Speed of 168 mph/h
Y – Maximum Speed of 186 mph/h
(Y) – Maximum Speed of 186+ mph/h
Note: You should put the speed index into consideration instead of ZR while choosing the tire.
What is the Difference Between ZR and R Tires?
While R indicates the radial construction, ZR is used for remarking high-speed capability.
Since ZR and R tires both have radial construction, there is no difference for the same speed rating.
For instance, 245/45ZR17 91(Y) and 245/45R91(Y) tires have same capabilities for a same pattern.
ZR is the old-school way to indicate performance tires. There is no difference between ZR and R. In this case, you should check the load and speed index instead of R or ZR which indicates the same internal structures.
If you’re struggling to choose the best fit for your vehicle,
TireRack’s Tire Decision Tool:
I hope the article was helpful. If you have any further questions, please leave them in the below section. Have a safe ride folks!
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