Someone had a good suggestion which is to clean the brake rotors with alcohol to remove any oils before first riding.

500 Watt (1000 Watt Peak)
48V 15.6 amp hour Battery
Good Torque
7 Speed Shimano Gear Shifter
Dual Front and Rear Suspension
Projector Headlight and LED Brake Light
20 x 4.0 Fat Tires
Front and Rear Disc Brakes
Motorcycle Style Controls
Multi Color Display
Electric Horn
Removable, lockable battery
2 Amp Charger UL certified

$849 + Tax , Free Shipping while using $50 off coupon

Also known as the Z8 , RidingTimes

JOYWAY Electric Bicycle for Adults Commuting Electric Mountain Bike https://a.co/d/cuG7Keu