mtb_addict Dude based on your posts in mechanics, you are in china with limited tools, hard to het parts, etc. Forget about an conversion. it is simple even poor calipers will brake better than rod brakes. if you have concern get the bike with caliper brakes and make you life simple
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Life is too short not to ride the best bike you have, as much as you can
(looking for Torpado Super light frame/fork or for Raleigh International frame fork 58cm)