Are pedals universally interchangeable?
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Yes, depending on your crankset. A 1-piece crankset uses 1/2″ pedals, while 2 and 3 piece cranksets use 9/6″ pedals.
Is a bike pedal left or right?
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Bike pedals come in left and right pairs. Each one should have an R or L mark somewhere on it. The pedal should thread in straight on its proper side.