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The motorcycle tyre size is indicated on its sidewall. But how do you figure out this sequence of numbers and letters? Find out in this article.
Contents of the article:
There are a number of elements that determine the size of a tyre. As you will see, it is not just the ratio of height to width. The size of a tyre also contains other important information that defines its type of construction and the limits of its capabilities.
Let's take a concrete example with the MICHELIN Road 6:
As you can see, the sidewall of the tyre shows the following dimensions:
180/55 ZR 17 then: M/C (73W)
Here is what these codes mean:
A radial tyre is identified by the letter R on the tyre
Radial tyres provide greater comfort at high speeds as a result of their soft sidewalls which absorb the impact of imperfections on the road surface. Radial tyres are needed for powerful vehicles with very rigid chassis and sporty purposes. A radial tyre is identified by the letter R on the tyre. (e.g: 120/70 R 15)
A bias tyre is identified by a dash
Bias tyres are able to carry a greater weight because their sidewalls are more rigid. They are suitable for vehicles travelling at moderate speeds, with small to medium-sized engines and flexible chassis.
A bias tyre is identified by a dash (e.g: 120/70 - 12).
A bias belted tyre is identified by the letter B on the tyre
Bias-belted tyres are so called because a "belt" strengthens the tyre section. This reinforced version of the bias is more suitable for heavy motorcycles.
A bias belted tyre is identified by the letter B on the tyre (e.g: 180/65 B 16).
Now that you know the generalities, let's review the motorcycle tyre sizes for specific uses.
If you ride on the road, you are legally committed to the dimensions recommended by the manufacturer of your motorbike. These dimensions are the ones that are marked on your original tyres if you have never changed them.
But as we shall see, these obligations do not apply if you ride exclusively on other types of terrain.
If you only ride off-road, you are not bound by the legal requirements for road use. Therefore, it is possible to choose tyre sizes according to criteria that are important for your use.
For Enduro and motocross, some riders may opt for a narrower tyre for better handling. Others choose a wider tyre for more grip with studs.
Note that the dimensions are not the same for these two off-road disciplines. The width of motocross tyres is measured at the base of the studs, whereas the width of enduro tyres is measured at the widest point, i.e. the top of the studs.
To make sure you choose the right dimensions, refer to this enduro / motocross tyre sizes correspondence table:
For the track, some riders mount a wider tyre at the rear in order to get more grip. The disadvantage is that this reduces the handling of the bike.
Competition tyres usually carry the acronym NHS (Not for Highway Service). This indicates that these tyres are not approved for road use.
If you have an older motorbike, you may be having difficulty finding the right dimensions to replace your tyre, as the nomenclature has changed over time. Originally in inches, the tyre dimensions have now become standardised in millimetres (with the exception of the rim diameter which has remained in inches).
Fortunately, you can find compatible dimensions.
You can find the correspondence between the dimensions in inches and the dimensions in millimetres in this table:
DIMENSIONS IN MM
DIMENSIONS IN INCHES
2.75 - 3.00
3.00 - 3.25 - 3.60
3.50 - 4.10
4.00 - 4.10 - 4.60
4.25 - 4.50 - 4.60
4.25 - 4.50
4.50 - 4.60 - 5.10
4.50 - 5.10 - 5.50
5.10 - 5.50
Also note that the alphanumeric system is still used on certain Harley Davidson and other American custom bike tyres.
If you have one, you will find the corresponding dimensions in this table:
ALPHANUMERIC SIZE MARKINGS
METRIC SIZE MARKINGS
You now have the essential information on motorcycle tyre sizes.
With our tool below you can easily find the best motorcycle tyre for your needs.