These days (touch wood) the best folding bikes are pretty reliable, clocking up a similar mileage between failures to a conventional bicycle, but wheel rims and spokes can still cause problems on hard-used small-wheelers.We’re not sure why the spokes suffer, but most of the problems with rims are caused by the brakes. A 16-inch rim has little more than half the braking area of a big wheel, so it can overheat on long descents, and will wear out at least twice as fast.Worn rims can be dangerous, but even if they don’t disintegrate, rebuilding a wheel can be a time-consuming and/or expensive process.
Internal drum brakes are an obvious solution, and they’re fairly easy to fit to most folders if you have the time and the inclination. But you won’t get one on the Brompton, which has a slender 72mm front ‘drop-out’ width.Various attempts have been made to slice drum brakes down to size over the years, but there were always technical problems.The answer came – as it so often does – with a bit of lateral thinking.The Australian-made Greenspeed recumbent trike uses Sturmey Archer drums, and Greenspeed remanufactures the hubs to reduce the 100mm width.When the company took on the sideline of distributing the Brompton last year, it occurred to proprietor Ian Sims that with a little more machining, the Sturmey brake might be squeezed onto the Brompton.
Bred on the antipodean HPV racing circuits, the Greenspeed/Sturmey hub is substantially stronger than a normal Brompton wheel, with oversize 12mm ball-bearings (normal Sturmey bearings are 10mm) and 36 instead of 28 spokes.The result is a rigid, maintenance-free front wheel and consistent braking in all weather conditions.
Fitting & Removal
Very easy.The hub brake comes with a long torque reaction arm that slots into a clamp placed around the fork. It’s then just a case of refitting the cable. Brompton cable runs are precisely measured and the cables can get in a tangle if misrouted or misaligned. It’s essential that the front brake cable runs in front of the other two and down through the cable gatherer brazed to the right side of the frame. If it doesn’t, something will get trapped when the bike is folded. By pure chance, the standard outer cable is about the right length for the Sturmey hub, but a longer inner cable will be needed.
Drum brakes are generally a heavy option, but this narrow hub isn’t too bad, giving a total wheel weight of 1,120g. Subtract the weight of the old wheel and caliper brake, and the net gain is only 385g, or just under a pound, which is quite acceptable for a stronger and more reliable wheel.
With the flange removed, the off-side spokes anchor directly into the drum
Removing the wheel is particularly easy – the axle nuts come off as usual, the cable slips off and the torque arm slides out.The operation is cleaner too, because the rim isn’t caked in the usual slippery mixture of oil and aluminium powder, and there’s no caliper to trap mud and debris. Another advantage of doing away with the caliper is that the tyre can be inflated before you refit it – useful if you’re struggling to repair a puncture.
On the road, the first impression is of near silence compared to a caliper or V-brake. The drum is powerful, but progressive. A gentle squeeze on the lever gives a strong stop of 0.3G – 0.4G, but grab the lever in panic and brake force rarely exceeds 0.56G. In practice, this means that a drum brake is less likely to send you flying over the handlebars than a fiercer and less forgiving V-brake.The drum will also be unaffected by water, oil or mud. In extreme conditions it gets warm, but there’s no risk to the tyre, and it soon cools down. The rear caliper brake is still grinding away at the rim, of course, but we found we tended to make more use of the front drum, so rear brake life should be slightly extended too. When you come to fold the bike, the cleaner front wheel is very welcome.
Two small provisos: if you ride through a deep flood, the drum brake could be out of action for some time, and ours had a slight judder, possibly a side-effect of the adaptation.
Conclusion
The Greenspeed hub seems good value for money, and in terms of servicing, it should prove to be fit-and-forget technology. If your Brompton has a tendency to eat rims, spokes or bearings, a drum brake upgrade will pay for itself fairly quickly, even ignoring the hassle of breakdowns and the danger of exploding rims. It also looks jolly nice, should aesthetics influence you in any way.
Brompton front drum conversion
Price £80 (hub only), or £120 (entire kit), plus £10 to £15 postage outside Australia. Greenspeed Recumbent Trikes tel +61 3 9758 5088 mail ian@greenspeed.com.au
UK Distributor: Westcountry Recumbents
A to B 48 – June 2005
