After much faffing, swearing, sweating, and 3 different bottom bracket tools, I've finally completed the upgrade of my Brompton to a 16 speed configuration.
I found on my trips last year that the 33/20 1:1 bottom gear on the 16" wheel just wasn't low enough for any real hill climbing, meaning that I would spend too much time pushing her up the hills.
Because of the peculiarities of the Brompton rear frame I couldn't put a bigger gear on at the back, meaning I'd have to reduce the size of the gear at the front. Finding smaller single chainrings than 33 tooth proved next to impossible so it occurred to me (inspired by a friend), to put a dual chainring on the front with a small chainring. Long story short I ended up putting a triple crank on the front with a 28, 39 and a chain guard in the 3rd slot. Because there is no room for a derailure, changing between chainrings is a case of getting off and moving the chain manually. But it's sort of like the low range/high range on a land rover. When I know I'm about to go up a hill I can set it to low range, when I cross the border to the Netherlands, I can set it to high range...
All in all this has dropped the whole gear range by about 17% for low range, and increased it by 17% on the high range. If I've done my maths right, this gives me a tiny 1.85m bottom gear, and a nice big 8.18m top gear.
I'll post some photos when it's day light. I just took her out and cycled all the way to the top of the hill behind my flat without needing to get off and push, I'm considering that a success.
J
I found on my trips last year that the 33/20 1:1 bottom gear on the 16" wheel just wasn't low enough for any real hill climbing, meaning that I would spend too much time pushing her up the hills.
Because of the peculiarities of the Brompton rear frame I couldn't put a bigger gear on at the back, meaning I'd have to reduce the size of the gear at the front. Finding smaller single chainrings than 33 tooth proved next to impossible so it occurred to me (inspired by a friend), to put a dual chainring on the front with a small chainring. Long story short I ended up putting a triple crank on the front with a 28, 39 and a chain guard in the 3rd slot. Because there is no room for a derailure, changing between chainrings is a case of getting off and moving the chain manually. But it's sort of like the low range/high range on a land rover. When I know I'm about to go up a hill I can set it to low range, when I cross the border to the Netherlands, I can set it to high range...
All in all this has dropped the whole gear range by about 17% for low range, and increased it by 17% on the high range. If I've done my maths right, this gives me a tiny 1.85m bottom gear, and a nice big 8.18m top gear.
I'll post some photos when it's day light. I just took her out and cycled all the way to the top of the hill behind my flat without needing to get off and push, I'm considering that a success.
J
