Motorcycle Tyre Sizes Explained, Bike Tyre Size Guide
Bike Tyre sizes explained
Bike Tire Sizes Explained ('Tyre' or 'Tire' in US English)
Bike Tyre sizes explained as follows with the use of the above picture. The tyre Size is written on the sidewall of the tyre as 120/70 ZR 17. Here the 120 is the section width in millimeters (mm) as detailed in the diagram on the right. The second figure 70 is the 'Aspect Ratio', which is the value of the section height in millimeters divided by the section width in millimeters and then multiplied by 100 to give a percent value. Here it means that the height of the tyre is 70% of the width of the tyre. A low figure means a wider tyre aspect ratio.
This is followed by the letters 'ZR'. The 'R' stands for a 'Radial Tyre' (to know more about radial tyres visit our site www.BestCarsinIndia.Com). The 'Z' is the speed rating and the speed rating symbols are given below in a table. This is followed by '17' which is the diameter of the rim in inches on which the tyre is to be fitted. It may be noted that the tyre width and height are in metric system in millimeters, but the rim size is in inch. This is because rim sizes are specified in inches universally almost all over the world.
In India motorcycle tyre sizes are written as shown on the right - 90/80-17. As above 90 is the section width in millimeters and 80 is the Aspect Ratio - that is the tyre height is 80% of the width of 90mm or 0.8x90=72mm. This is followed by a dash because it is not a radial tyre and also since the speed rating is marked after the rim diameter of 17 inches.
Tyre sizes in inches are also commonly specified in the case of motorcycle tyres, for example 3.5"x17 . In these cases the width of the tyre is given in inches and no aspect ratio is mentioned. When no Aspect Ratio is included in the tyre size, it means a 100% Aspect Ratio, that is the section width of the tyre is equal to the section height. This same tyre in the normal metric system would be written as 90/100-17. The 90 is obtained by multiplying the 3.5 inch width by 25.4, since one inch is equal to 25.4mm, that is 3.5x25.4=88.9 rounded off as 90mm. 100 is the aspect ratio and Rim diameter of 17 inches remains the same.
The advantages of having tubeless tyres are
- Since tubeless tyres have no tubes, the tyre assembly is lighter and thus helps in better control of the bike while cornering and during braking. Also improves petrol milage of the bike.
- In a tubeless tyre, in case of a puncture by a nail for example, the air leakage is very slow and there is no loss of control of the bike. You can continue to use the bike for some time, topping up tyre air pressure at petrol pumps whenever you go to fill petrol. In a tubed tyre, all the air escapes out of the tube and the tyre is blown out of the rim causing a blowout with a loud bang. You will lose control of the bike if you are travelling at a speed and is thus is very dangerous.
- A tubeless tyre runs much cooler than a tubed tyre because there is is no heat generated due to the friction between the tube and tyre when the tyre is rolling over the road. Thus cool tubless tyres last much longer than the hot running tubed tyres.
- Tubless tyres have less rolling resistance on the road, so you get more mileage or more kilometers per liter of petrol.
Cross or Bias Ply Radial Ply
The main difference between ordinary tyres and radial tyres is in the way the reinforcing tyre cords are wound during the tyre construction process. In the figure above you can see how the reinforcing cords are arranged in the Cross or Bias Ply Tyre and the Radial Tyre.
The pictures on the right gives a front view for better understanding the difference between ordinary Cross bias ply and radial tyres. The radial tyres are a much stronger construction since the reinforcing cords of the tyres are in the same direction as the forces acting on the tyre. In the case of the cross ply or bias ply tyre the cords are at an angle of 45 degrees to the forces acting on a tyre and thus does not offer the same reinforcement strength.
Radial tyres are always tubeless tyres with all the advantages of tubeless tyres. In addition Radial Tyres have great many other advantages as explained in our website www.BestCarsinIndia.Com