How to decode motorcycle tyre’s sidewall markings?

There must have been many times when you have wondered about what does the numbers written on your bike’s tyres mean? Well good news is that this is the information that differentiates a tyre from another and it’s no rocket science to decode the same. Do not be embarrassed if you’ve been riding bikes from a long time now but still had no idea about these tyre sidewall markings, because in the article below we share the information which will allow you to read the tyres of your motorbike.

Basically all the tyres come along with the standard information which appears in this format as example 120/70 ZR17 M/C (58W), apart from this information some tyres are tagged with the specific ‘XYZ’ tyre model name and the company name which has manufactured the tyre.

tyre sidewall

Tyre width

The number which appears first in the code denominates the tyre width. For example in the code ‘120/70 ZR17 M/C (58W)’, 120 is the tyre width and it is always measured in millimeters or ‘mm’ from sidewall to sidewall. The width of the tyre is a major factor in determining the handling and turning characteristics of a bike. The bigger the width of the tyre is, the more surface area it will cover, hence greater grip. At the same time a fatter tyre makes for a motorcycle which is comparatively harder to turn in and this is one of the reasons why cruisers with fat rear tyres are lazy to turn into a corner.  

Aspect Ration or Height-

The following numbers in the code ‘70’ denote the aspect ratio of a tyre, or it is sometimes also referred as height. The number which is present in the code, unlike width is not expressed in ‘mm’ but as a percentage figure of its width. In simple details, in this case the aspect ratio is 70% of the 120mm width, making it 84mm.

tyre sidewall

Wheel diameter-

Usually on a sports bike the next code digits are ‘ZR’. The Z denotes the speed rating of the tyre while the R simply means that is a radial type tyre. In the above code, Z denotes that this tyre is rated above 240kmph or 149mph. The following number ‘17’ signifies the diameter of the tyre in inches, and in this case the tyre is of 17inch diameter. ‘M/C’ in the code says that this is a motorcycle tyre.

Load index and speed rating-

The last bit of information on the code is ‘58W’ but you will need the chart below to decode the same. This code is very critical when buying a new tyre and it is called load and speed index of the tyre. In the present case, the number ‘58’ signifies that the motorcycle tyre can carry a maximum weight of 236kgs at maximum pressure. And the ‘W’ rating says that the tyre can do a maximum top speed of 270kmph when properly inflated and loaded. This is called as the load index & speed rating of a tyre which should always be matched when ever making a new tyre purchase.

tyre sidewall

Note – Always recommended that your tyre rating should match up with the performance of your motorcycle as it is very risky to run a low performance tyre on a high performance bike.

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