Honda PIONEER SXS500M 2020 Owner's Manual page 164

Brakes
Brake Pad Wear
Refer to Safety Precautions on page 91.
Brake pad wear will depend upon the severity of usage and driving
conditions. The pads will wear faster in wet, sandy, or muddy
conditions.Inspect the pads during all regular service intervals to
determine the pad wear.
Note that the pads are designed to make a metallic noise during
braking when they reach the wear limit.
Front:
If you hear a continuous metallic friction sound when applying the
brakes, the brake pads need to be replaced. Have the vehicle
checked by a dealer.
Rear:
Check the wear indicator. If the wear indicator aligns with the
reference mark, replace both pads as a set, see your dealer for this
service.
RIGHT REAR
reference mark
brake caliper
wear indicator
Servicing Your Honda 157