>>1437063to keep the (almost) same gear ratio whist having better durability (due to more teeth being in contact with the chain)
you add one tooth to the rear sprocket for every three added to the front chain ring
48x14 (3.43) a
51x15 (3.40) b
54x16 (3.38) c
57x17 (3.35) d
60x18 (3.33) e
26x1.75 wheel
170 mm crank arms at 100 rpm to give km/h of
41.89 a
41.52 b
41.28 c
40.91 d
40.67 e
unfortunately such large chain rings tend towards a 130 mm Pitch Circle Diameter (five arm)
54 tooth with 110 mm pcd (four arm)
http://www.stronglight.com/stronglight/index.php/welcome/afficher_Produit?id=704so depending on what is available you can get a double chain ring with
54 tooth outer ring for speed
34 tooth inner ring for climbing of hills
and assemble a Freehub cassette from 16 to 28 teeth
6 to 8 speed chains are 7mm thick
9 speed chains for MTB use are 7 mm thick
but 9 speed chains for road bikes may be 6.5 mm thick
last problem being Derailleurs
front Derailleurs there is needed Max Ring Difference of something like 26
54-26=28
60-26=34
rear Derailleurs are more complex
they can tolerate a front difference of around 20 (depends on model)
and can have a Chain wrap / Capacity of around 40 teeth (depends on model -SGS?)
so 54-34=20 (Maximum Chain ring Difference)
and 28-16=12 (Maximum Cassette Cog Difference)
20+12=32 (Total Drive train Capacity use)
only just within the total capacity limit for a medium cage (GS) MTB Derailleur
ymmv
