After lowering the gearing on the Brompton
in December, I found the bike much easier and much more enjoyable to ride. The downside of this was that the gearing on the DL-1
now seemed to be ridiculously high by comparison. Whilst I had lowered the gearing on the DL-1
when I first purchased it, by replacing the rear sprocket, the stock gearing was obscenely high and this reduction never really felt like enough. Whilst an even larger sprocket could have been substituted on the rear, the reduction in gearing this would have brought would be limited; the current sprocket is a 21-tooth, and I believe they only go up to 24-tooth sprockets for this type of hub. Add to that the spatial constraint imposed by the chaincase and the only option left was to replace the chainset.
The chaincase made finding a replacement chainset difficult, due to the problems with crank arm clearance. There didn’t seem to be a lot of information out there online, so I took the plunge and bought a Stronglight
chainset which looked like it might fit. It quickly became obvious that it would not fit, and so this became the chainset I used on the Brompton
instead. Eventually I spotted a promising looking chainset on David Hembrow’s shop
and asked him about the dimensions
. Reasonably convinced I could make it fit, I ordered the chainset and it arrived last week.
The new chainset is a 38-tooth, replacing the original 46-tooth one. It sits within the confines of the steel chaincase pretty well, although the chainset cover had to be modified with a metal file.
The chainset cover is basically a paint-tin lid with a hole in it to accommodate the crank arm and a removable plate to allow it to pass over the pedal. The base of the new crank arm is slightly thicker than the original one, so it had to be filed a bit to accommodate it
The filing is a bit rough, but functional. It doesn’t look this bad when fitted to the bike. The result is much the same as it was with the Brompton, the bike is generally much easier and much more enjoyable to ride. Whilst I did use the highest gear occasionally, oddly enough I do not find myself missing it.
I also attempted to switch the left crank so that the left and right would match, however the left crank is stuck on so well that it broke my crank puller tool. The tool was originally part of my Edinburgh Bicycle Co-operativecycle tool kit, many of the tools from which have since broken through normal use. Needless to say, I would not recommend. Until I get a replacement, it appears I am stuck with odd cranks.
Sturmey Archer recommend that you use at least a 2:1 ratio for the number of teeth on the chainring relative to the sprocket. With this modification, I have gone below that minimum, to around 1.8:1. Whilst not officially recommended, I expect this will not cause any problems. It is likely that the 2:1 ratio is erring on the side of caution, and combined with the large wheels of the DL-1, I expect that I will not be pushing the hub beyond what it can take. The new smaller chainset will prove beneficial when I eventually realise my dream of re-building the rear wheel around an eight-speed hub to increase the useful range of the bike sometime in the future.