Brompton Touring Bike

A few weeks ago I did a repair job on a pair of vintage Dahon folding bikes. One had 16" wheels and the other, 20" wheels. Although the concept of a folding bike was intriguing, these two bikes were a bit wobbly and lacked the stiffness and quality components that I was accustomed to in working with touring bikes. However, this whole episode got me contemplating the positive points of folding bicycles in general so I began studying the various offerings and their ride qualities. Well, you don't get too far down that rabbit hole before stumbling upon the cult of Brompton owners. The "Brompton" is a British manufactured folding bicycle designed in the 1970's which has a following of thousands of loyal users. The bike folds down into a very small package which is relatively light weight for a steel framed bicycle. The hinges are stout and stiff and the moving parts are minimal and less than sophisticated and the bike does exactly what it is advertised to do. It rides much like a standard large wheeled bike but can easily be folded up into a 22" x 21" x 10" package for carrying onto planes, boats, trains or…

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Brompton Gearing Modifications

Various gearing modifications have been attempted for the Brompton folding bicycle over the past decade to boost the ratios and have these bikes fulfill a broader function. Although the 6 speed (2x3) factory version has been successfully used for distance loaded touring, it barely squeaks by in overall gear ratios for a true "touring bike". Rohloff 14 speed hub conversions are very expensive, very heavy (about a pound heavier) and they add a great deal of width to the original folding size. A typical Rohloff conversion costs close to $3500 USD and that is not including the original cost of the Brompton bike. The Shimano 8 & 11 speed hubs also use wider drop-outs of 135mm having the same problems that the Rohloff conversions do but without the solid reliability of the German made hub. For some years now a few Brompton custom shops have been adding an additional sprocket (triple cog kit) to extend a 6-speed Brompton's gear range from 302% to 368%.  This gives 9 distinct gears and takes care of the gearing problem, however, the conversion is tricky often needing to grind metal from the frame to make room for the additional parts as well as swapping out the Brompton 6 speed chain for…

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