changing gear

i have a subrosa malum and it comes with gear 16t - 48t and i want to change rear freewheel to 13t and what could be the best size of sprocket to use on a front?!

thanks

cheaper to keep the 48t chainring and just get an appropriate rear sprocket

size depends on what kind of ratio you wish to have. if you are comfortable with 48/16 on a freewheel I would consider a 17 tooth sprocket for riding fixed as it will be fairly easy to resist for slowing down the bike

i wanna set on bmx 3 piece cranks with bmx sprocket and 48/16 is too heavy for me, i'm looking for a lighter gear

so go to 49 17 or 48 19

i run 48 19 and it is great as I can spin down hills at 38 miles an hour but also get up steep inclines too

39 13 is about the same as you have now so I guess you want a 38 or 37 chainring if you want to make it a bit easier.

so go to 49 17 or 48 19

i run 48 19 and it is great as I can spin down hills at 38 miles an hour but also get up steep inclines too

Swoon

39 13 is about the same as you have now so I guess you want a 38 or 37 chainring if you want to make it a bit easier.

What about 13t/36t?

According to the app on my phone:

48 / 16 = 79.1 GI
48 / 17 = 74.5 GI (the gear I ride at the mo)
48 / 19 = 66.6 GI (the gear DJ likes)

39 / 13 = 79.1 GI
38 / 13 = 77.1 GI
37 / 13 = 75.1 GI
36 / 13 = 73 GI
34 / 13 = 69 GI
32 / 13 = 64.9 GI
30 / 13 = 60.9 GI

Higher GI = tougher to pedal. Take your pick.

butters repped for giving the op the answer he needed.