chain plates 2 and the sleeve 3 together accordingly by connecting multiple inner chain plates 1 outer chain plates 2 and sleeves 3 in series a loop of chain is formed now referred to fig3 the shape of the protruding portion 23 of the outer chain plate 2 is significantly indicated the protruding portion 23 improves the tensile strength and flexibility of the drive chain so as to promote its impact withstanding strength in conjunction with a nine speed variable flywheel for upgrading its safety fig4 shows the combination of the drive chain and a smallest flywheel plate 51 and fig5 is a sectional view showing a local part of the combination illustrated in fig4 whereas the clearance between each tooth root of the smallest flywheel plate 51 provided on its outer peripheral a total of eleven teeth and the smallest flywheel plate 51 is very small at approximately 0 5 mm as designated by size a in fig5 the protruding portion 23 provided on the single side of the outer chain plate 2 is capable of increasing the tensile strength of the drive chain without hitting the root of the tooth the protruding wall 24 provided on the first side 25 of the outer chain plate 2 that contacts the bottom of the gear disk 5 as illustrated in fig5 helps faster and more reliable achievement of positioning for the speed varying function as illustrated in fig6 the drive chain in the course of varying speed while moving is found mild deformation the protruding wall 24 disposed on single side of the outer chain plate 2 prevents the drive chain from hitting its neighboring.