INTRODUCTION
When considering motorcycle tire replacement, it is 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 need to 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 (73 W) TL
A typical code for the rear tire of a larger capacity motorcycle is shown above. Below is an explanation of each item.
190
Tire width: measured in millimeters at its widest point
fifty
Aspect Ratio – The aspect ratio is the height of the rim’s sidewall in relation to its width (displayed as a percentage). So with this example the height of the side wall will be 50% of 190 millimeters = 95 millimeters.
Z
Speed Rating – In this particular tire code, the ‘Z’ is one of two speed ratings. Although the ‘Z’ indicates that the tire is suitable for speeds upon 240 kph (149 mph), does not 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 kilometers per hour (106 mph)
S = 180 km / h (112 mph)
T = 190 kilometers per hour (118 mph)
U = 200 kilometers per hour (124 mph)
H = 210 km / h (130 mph)
V = 240 km / h (149 mph)
Z = More than 240 kph (149 mph)
W = 270 kilometers per hour (168 mph)
Y = 300 km / h (186 mph)
R
Construction type – R = Radial construction. B = Bias belt construction.
Note: If omitted, the tire will have a cross-ply construction.
17
Wheel Rim Diameter – This is the diameter of the wheel that fits the rim, measured in inches.
73
Load Index – To find the actual weight the number represents, you will need to refer to the ‘Load Index’ table for a tire. With this example, 73 = 365 kg (805 lbs). Most manufacturers also set the maximum load in kilograms and pounds elsewhere on the side of the tire, thus eliminating the need for a ‘Load Index’ table.
W
Speed Rating – Usually shown in parentheses with the load index number. The load applied to the tire influences its maximum speed, which is why the two are shown together. Using this example, the tire’s maximum speed will be 270 kph (168 mph) when its maximum load is 365 kg (805 lbs). When not under maximum load, the tire can be safely operated at higher speeds. In the unlikely event that you routinely drive at speeds that exceed the speed rating of your own tires, contact the tire manufacturer for advice or refer to the ETRTO (European Tire and Rim Technical Organization) guidelines.
TL
TL = tubeless.
TT = Tube type (an air chamber must be used).
OTHER TIRE BRANDS
Rotation Direction Arrow: The tire should rotate in the direction of the arrow when the motorcycle is moving forward.
Manufacture Date: Usually shown as a 4-digit number. The first two digits represent the week of manufacture, the second two 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: The rubber in tires will degrade over time, even when not installed on a vehicle. Although there is no hard and fast rule about how old it 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 rise 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 must be replaced. A small triangle is often used on the side wall to show its position.
M / C – Suitable for motorcycle use.
MAX. PSI – The maximum pressure the tire can inflate to in pounds per square inch.
MAX. BAR: the maximum pressure the tire can be inflated to in Bar. This is the standard pressure unit in most European countries outside the UK (1 bar = 14.50 psi).
E Mark. – Tires sold in Europe must meet 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 American equivalent is the DOT (Department of Transportation) code.
Dave roffe