The Citezen Bike has a 48T front chainring and a 6 speed freewheel. What are the ratios is it 13- 28 or 14-28 . The specifications are incomplete .If the rear freewheel craps out you can always remove it and replace it with a fixed gear cog .I recommend a shimano dura ace cog from loose screws bicycle small parts. (Look it up this is not a link) or you can replace it with a 16T bmx freewheel . Do not forget to adjust the chainline though or you can have problems.