![]() ![]() At 86″, top gear was the same, but first was reduced from 46″ to 40″. The company decided to fit 13- and 15-tooth sprockets.The very similar sizes helped to give a slick gear change and resulted in evenly-spaced ratios.The bad news was a rather disappointing overall gear range of 215%, which was not much more than the 187% of the basic 3-speed. It all sounds a bit Heath Robinson, but engineered with Brompton’s usual attention to detail, the 6-speed soon established itself as a neat and efficient conversion. On a basic 3- speed hub-geared variant, the tensioner only moves when the bike is folded, but by fitting tensioner wheels designed to ‘float’ from side to side, it was possible to fit two sprockets side by side, doubling the number of gears. The new system took advantage of the Brompton chain tensioner. Other bike manufacturers migrated to the similar SRAM 5-speed, but the Brompton frame is unusually narrow, and it was not until May 2002 that the company came up with its own solution – the 6-speed (more correctly 2×3-speed) SRAM/Brompton derailleur/hub gear. Long-term readers may recall that the bankruptcy of hub gear manufacturer Sturmey Archer in the summer of 2000 left Brompton short of a suitable 5-speed hub.
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