I have a Redline racing bike 20 inch i beleive that im converting into a bmx bike. the bike is basic. it has bad one piece cranks that i want to switch out and i want new pedals, also it has a fixed gear i want to take off. what i want to know, is since my bike is fairly small, how do i know what cranks will fit it? and is it possible to switch the fixed gear completely off and what parts do i need?