A rear derailleur cage moves mere millimeters with each click of a button. It’s a subtle change but enough to move a bike’s chain from one gear to the next. Or not, as Mark Cavendish found out in the closing meters of stage seven of the Tour de France this year.
On the finishing straight his derailleur was fractions of a millimeter out skipping the chain between gears. Cavendish, streaking ahead of the best sprinters in the world, was less than a millimeter from victory. He had been robbed of momentum and glory in the Bordeaux streets by a rear shifter behaving as if it had been imbibing the local produce. His best chance yet at a historic 35th Tour de France stage win literally derailed.
