There's no set length for all 16" bikes. It depends on the proportions of the frame and the gear ratio it's set up with.
When purchasing a bike pedal for a bike with a 9/16 inch thread size, look for a pedal that is compatible with a 9/16 inch thread size.
The standard wheel size of a Brompton bike is 16 inches.
The standard thread size for a bike pedal is 9/16 inch.
The thread size of the pedal on a Trek bike is typically 9/16 inches.
The standard threading size for bike pedal threading is 9/16 inch.
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16 inch
A 16-inch bike is typically suitable for children around 4 to 6 years old.
The standard bike pedal bolt size for most bicycles is 9/16 inch.
The standard bike pedal nut size for most bicycles is 9/16 inch.
The standard thread size for mountain bike pedal installation is 9/16 inch.
A 5'2 woman should ride a bike with a frame size of around 15-16 inches.