what size wrench is needed to change bike pedals
A quality pedal wrench will be long enough (and preferably with angled openings) to provide significant leverage, and durable enough to allow repeated application of such force. Pedal wrench flats are typically 15mm in size. 9/16 (~14.3mm) is somewhat common on older pedals. 17mm and other sizes have been used, but you aren't very likely to encounter them. (A cone wrench is thinner and shorter than a pedal wrench, and unable to provide appropriate durability or leverage for use on pedals.