Scooter or Bike Tyre Marking Decoded: Know Complete Details Here

Scooter or Bike Tyre Marking Decoded: Know Complete Details Here

Featured Stories by Team Drivio | Jul 29, 2023

There are usually 4-5 readings on the tyres of every two-wheeler.

  • From checking tyre pressures to seeing if they’re radial units or not, there are a lot of things to consider. 
  • Radial tyres are usually a fair bit more grippy than non-radial/nylon ones. 
  • The last letter, meanwhile, signifies the tyre’s speed rating. 

You might have often seen people talk about maintaining tyres and being able to read them. And that would’ve made you consider the importance of the same. If it puzzles you too, here’s why being able to read your tyre is so important.

Why Is Two-wheeler Tyre Reading Important? 

The contact between your two-wheeler and the road while in motion is solely through the tyres. Therefore, it is crucial to ensure that the tyres on your two-wheeler are the correct specification to avoid undesirable consequences. If the tyres are not suitable for the vehicle, various issues can arise. 

To facilitate clear communication between manufacturers and consumers regarding tyre specifications, a well-defined nomenclature for tyres exists. Reputable manufacturers label all their tyres with specific codes that provide essential information about the tyre's capabilities. Here’s a quick guide to help you do the same: 

Tyre Size, Load & Speed Rating

Consider a tyre with 180 / 50 R17 71 W written on it as an example. Here’s what each engraved thing means: 

Tyre Width

The initial two or three digits in the marking indicate the section width of the tyre in millimetres (mm), measured from the widest points of the sidewalls (not the contact patch) when the tyre is properly inflated according to its correct specification. In the given example, the number 180 signifies a tyre width of 180mm. This is followed by a forward slash '/' to separate the next number in the marking.

Aspect Ratio / Profile

Following the section width marking, the subsequent digits in the tyre specification indicate the aspect ratio. This aspect ratio represents the height of the sidewall or the "profile" of the tyre. 

Usually expressed as a percentage of the tyre's section width, the aspect ratio in the provided example is 50. This means that the height of the tyre's sidewall is 50% or less of its nominal sectional width.

Tyre Construction

In certain cases (though not universally), the aspect ratio might be succeeded by a code denoting the construction type of the tyre. This code is represented by a letter from the alphabet, and its significance is as follows:

  • B - Represents bias belt or bias ply construction.
  • D - Indicates diagonal tyres, which are constructed using nylon cords positioned diagonally across each other in both the tread and sidewall.
  • R - Signifies radial tyres, which are constructed with layers of cords running radially from one bead to the other.

Wheel Diameter

Moving on to the next set of digits, they indicate the diameter of the wheel in inches. In the provided example, the number 17 denotes that the tyre is designed to fit 17-inch wheels.

Load Index

After the wheel diameter marking, the subsequent set of digits represents the load index. This load index indicates the maximum weight that the tyre is capable of carrying. Manufacturers provide a load index table for reference, which correlates the load index number to the corresponding maximum weight capacity. 

In some cases, tyre makers may also specify the maximum load capacity of the tyre separately, expressed in kilograms (kg). This information is crucial for ensuring that the tyre can safely support the weight of the vehicle and its occupants.

Speed Rating

Tyres cater to a wide range of two-wheelers, accommodating everything from slow-moving mopeds to high-performance superbikes capable of reaching incredibly high speeds. The maximum speed at which a tyre can safely travel is represented by its speed rating. This speed rating is conveyed through various formats, such as a single letter, a combination of a letter and a digit, or a letter enclosed in brackets. 

Just like load capacity, certain manufacturers may also specify the speed limit of the tyre, either in miles per hour (mph) or kilometres per hour (km/h), to ensure clarity for consumers.