As the tire tread wears down, the tire becomes more susceptible to puncture and failure. An accepted estimate is that 90% of all tire failures occur during the last 10% of tread life (90% worn). So it is false economy and unsafe to use the tires until they are bald.
If any measurement is less than the service limit, replace the tire (see Tire Removal/Installation in the Wheels/Tires chapter).

Tread Depth Standard:
Front 3.6 mm (0.14 in.)
Rear 5.3 mm (0.21 in.)
Service Limit:
Front 1 mm (0.04 in.) (AT, CH, DE) 1.6 mm (0.06 in.)
Rear 2 mm (0.08 in.) (Up to 130 km/h (80 mph)) 3 mm (0.12 in.) (Over 130 km/h (80 mph))
| WARNING Some replacement tires may adversely affect handling and cause an accident resulting in serious injury or death. To ensure proper handling and stability, use only the recommended standard tires for replacement, inflated to the standard pressure. |
NOTE
Wheel/Tire Damage Inspection
Wheel Bearing Damage InspectionAxle Inspection
Remove the front and rear axles (see Front/Rear Wheel
Removal).
Visually inspect the front and rear axle for damages.
If the axle is damaged or bent, replace it.
Place the axle in V blocks that are 100 mm (3.94 in.) [A]
apart, and set a dial gauge [B] on the axle at a point
halfway ...
Before Servicing
Before starting to perform an inspection service or carry out a disassembly
and reassembly operation
on a motorcycle, read the precautions given below. To facilitate actual
operations, notes, illustrations,
photographs, cautions, and detailed descriptions have been included in each
chapter w ...
Drive Chain
The drive chain slack and lubrication
must be checked each day before riding
the motorcycle and must be maintained
in accordance with the Periodic
Maintenance Chart for safety and to
prevent excessive wear. If the chain
becomes badly worn or maladjusted -
either too loose or too tight - the c ...