Honda GOLDWING GL1800/A 2015 Owner's Manual page 202

Brakes
Brake Pad Wear
Refer to Safety Precautions on page 154.
Brake pad wear depends upon the severity of usage, the type of riding, and road
conditions. Generally, the pads will wear faster on wet and dirty roads. Inspect
the pads at each regular maintenance interval (page 159).
Front Brake
LEFT FRONT (right side similar)
grooves
Always inspect both pads in both the right and left front brake calipers.
Check the grooves in each pad. If either pad is worn to the bottom of the
grooves, replace both pads as a set. See your dealer for this service.
Rear Brake
RIGHT REAR
cutouts
Check the cutouts in each pad. If either pad is worn to the cutout, replace both
pads as a set. See your dealer for this service.
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Servicing Your Honda