Copyright Goodheart-Willcox Co., Inc. 339 Chapter 16 ∣ Wheels and Tires Warning When replacing a tire, use the same size used by the original equipment manufacturer (OEM). Vehicle geometry is an important factor in motorcycle design, and changes in tire size can affect the machine’s handling and stabil- ity. For safety, never replace the original tire with a tire that is a different size. Speed, Load, and Compounds Letters in the tire size markings indicate the sustained speed at which the tire is safe. For example, a tire with an S marking has been tested at a sustained speed of 112 mph for six hours. Some modern motorcycles are capable of approximately 200 mph, requiring even higher rated tires. The following list shows the speed limits indicated by the letter markings: • S indicates 112 mph (180 km/h) maximum sustained speed. • H indicates 130 mph (208 km/h) maximum sustained speed. • V indicates 150 mph (240 km/h) maximum sustained speed. • Z indicates over 150 mph (240 km/h). Maximum load rating and maximum inflation pres- sure may also appear on the sidewall. A tire balancing mark may be provided and should be properly aligned with the valve stem. See Figure 16-33. Refer to the service man- ual for details. Different tire compounds and multi-compound tires are common today. With compounds, tires are made for specialized uses and for use in certain conditions. Off- road tires are able to perform on hard-packed terrain or in muddy conditions. On-road tires may use a soft compound for road racetracks. For touring, a multi-compound may be used to provide long-wearing center treads and a softer sidewall for flex. Tread Patterns Tread patterns and profiles vary depending on use and travel surface. For example, high-performance motorcycle tires are best for sport riding under extreme conditions. They may be heavily grooved with a deep tread pattern or different compounds. Universal tires are suitable for mul- tiple uses. They displace water when road surfaces are wet and provide good balance and grip on dry roads. Dual- purpose, or on- and off-road tires, are a type of universal tire. They work adequately all around but are not designed for high performance on any specific surface. Knobby designs are for off-road dirt riding, but there are some DOT-approved knobby designs available for specialized Tire code (Inch indication) 4.00 H-18 4PR Ply no.: 4-ply rating Rim diameter: 18 inch Tread width: 4 inch Speed limit code Tread width: 170 mm Aspect ratio = 60% Radial indication mark Speed limit code Max. load code Rim diameter: 18 inch 170/60 R 18 73 H Goodheart-Willcox Publisher Figure 16-31. Tire code inch indication. Goodheart-Willcox Publisher Figure 16-32. Tire code metric indication. Balancing mark Goodheart-Willcox Publisher Figure 16-33. A tire balancing mark should be properly aligned with the valve stem.