>>1407514its not really significant to the performance of the drive train
but the front chain ring should line up roughly with the middle of the rear cogset / freewheel / free hub
for a six speed cogset the space between each cog should be 5 mm and each cog roughly 2.5 mm thick
2.5x6=15 5x6=30
15+30=45
45/2=22.5
assume hub spacing of 126 mm
divide by 2 = 63
+ 22.5=85.5
126-85.5=40.5
>distance from lock nut to lock nut not accounted forso the front chain ring (might) be somewhere around 40.5 mm from the center line of the bottom bracket
of course every bike is slightly different
but I only really bought it up because of chain stay clearance
a larger chain ring may get quite close to the chain stay
and crank arms also have different offsets that affect how close the pedals will be to the chain stay
to have a guess at chain ring size
tooth count x chain pitch = circumference divided by π = diameter /2 = radius
.eg you current chain ring is 40x12.7=508 /3.14=161 /2=80mm radius
ways to alter this are
chaining spacers
Bottom Bracket spindle length to get the right off set (116.5?)
hollow tech bottom bracket (bb width becomes 90mm)(crank moved left or right with spacers)
putting dents in your chain stay with a broom handle and a hammer
what size are your wheels anyway ?
iirc in terms of gear ratio every three teeth added to the chain ring is the equivalent to removing one tooth at the rear
.eg 40x13 and 43x14 would be almost the same gear ratio
