Racing bike type mens geometry sloping comfort frame sizes xl l s m bike frame sizes cm 47 50 53 56 59 62 cm colour white model 2017 series bergamont prime frame material aluminium frame characteristics double butted hydroforming frame alloy 6066 aluminium fork material carbon aluminium gear system with derailleur number of gears 20 groupset shimano rear derailleur shimano tiagra front derailleur shimano tiagra gear shift brake lev