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 InspectionTie-Rod Removal
Squeeze the brake lever slowly and hold it with a band
[A].
Remove the front footpeg bracket bolts [A].
Raise the rear wheel off the ground with the jack (see
Rear Shock Absorber Removal).
Special Tools - Jack: 57001-1238
Jack Attachment: 57001-1608
Remove:
Upper ...
Crankshaft Sensor Peak Voltage Inspection
Refer to the Crankshaft Sensor Peak Voltage Inspection
in the Electrical System chapter.
If the reading is within the standard, remove the ECU and
check the wiring for continuity between harness connectors.
Special Tool - Hand Tester: 57001-1394
Disconnect the ECU and sensor connector ...
Stick Coil Primary Peak Voltage Inspection
NOTE
Be sure the battery is fully charged.
Remove the stick coils (see Stick Coil Removal).
Do not remove the spark plugs.
Connect the ECU to the harness.
Measure the primary peak voltage as follows.
Install the new spark plug [A] into each stick coil [B], and
ground them onto ...