When considering motorcycle tire replacement, it’s best not to take chances. If you want to use tires other than those recommended by your motorcycle manufacturer, there are many options available. But you must make sure that any deviation from what is recommended is suitable for your bike, safe and within the law. Understanding the information on the sidewall of a tire will help you make the right decision. A key part of that is the motorcycle tire code.
MOTORCYCLE TIRE CODE
190 / 50 ZR 17 (73W) TL
Shown above is a typical code for a larger capacity motorcycle rear tire. Below is an explanation of each item.
Tire Width – Measured at its widest point in millimeters
Aspect Ratio – The aspect ratio is the height of the tire’s sidewall relative to its width (displayed as a percentage). So, with this example, the sidewall height will be 50% of 190 millimeters = 95 millimeters.
Speed Rating – In this particular tire code, ‘Z’ is one of two speed ratings. Although the ‘Z’ indicates that the tire is suitable for speeds on 240 kph (149 mph), it doesn’t tell us the maximum allowed speed. An additional speed rating, shown in parentheses towards the end of the tire code, will provide this information. Both must be used in combination.
Other speed ratings:
R = 170 km/h (106 mph)
S = 180 km/h (112 mph)
T = 190km/h (118mph)
U = 200km/h (124mph)
H = 210km/h (130mph)
V = 240 km/h (149 mph)
Z = More than 240 km/h (149 mph)
W = 270km/h (168mph)
Y = 300 km/h (186 mph)
Type of construction – R = Radial construction. B = Bias-belted construction.
Note: If omitted, the tire will have a cross-ply construction.
Wheel Rim Diameter: This is the diameter of the wheel that fits the rim, measured in inches.
Load Index – To find the actual weight that the number represents, you will need to consult a tire ‘Load Index’ chart. With this example, 73 = 365 kg (805 lbs). Most manufacturers also list the maximum load in kilograms and pounds somewhere else on the sidewall of the tire, thus eliminating the need for a “Load Index” chart.
Speed Rating – Usually shown in parentheses with the load index number. The load applied to the tire has an effect on its top speed, which is why the two are shown together. With this example, the maximum speed for the tire will be 270 kph (168 mph) with its maximum load of 365 kg (805 lbs). When not under maximum load, the tire can be safely operated at higher speeds. In the unlikely event that you regularly drive at speeds higher than the speed rating of your own tyres, contact the tire manufacturer for advice or consult the ETRTO (European Tire and Rim Technical Organisation) guidelines.
TL = tubeless.
TT = Tubetype (an inner tube must be used).
OTHER BRANDS OF TIRES
Rotation direction arrow: the tire should rotate in the direction of the arrow when the motorcycle moves forward.
Date of Manufacture: Usually displayed as a 4-digit number. The first two digits represent the week of manufacture, the second two digits represent the year of manufacture. Example: 5107 will mean that the tire was manufactured in week 51 of 2007 (December 2007). Example: 0611 will mean that the tire was manufactured in the sixth week of 2011 (February 2011).
Note: Tire rubber will degrade over time, even when not installed on a vehicle. Although there is no hard and fast rule about how old is too old, it is generally accepted that tires should be replaced 5 or 6 years after their date of manufacture.
TWI (Tread Wear Indicator) – Most motorcycle tires have wear bars located within the tread grooves. The wear bars are raised about 2mm above the bottom of the tread groove and are placed in various places around the tire. When the tire has worn to the level of the wear bars, it should be replaced. A small triangle on the sidewall is often used to show its position.
M/C – Suitable for motorcycle use.
MAX PSI: The maximum pressure the tire can be inflated to in pounds per square inch.
MAX BAR – The maximum pressure to which the tire can be inflated in Bar. This is the standard unit of pressure in most European countries outside the UK (1 bar = 14.50 psi).
E marking. – Tires sold in Europe must comply with European standards and be marked with an ‘E’ code. The number following this letter will indicate the country that has approved the tire for road use. The US equivalent is the DOT (Department of Transportation) code.