<P> Use of hard shells declined rapidly among the general cyclist population during the 1990s, almost disappearing from road and cross country mountain bike helmets by the end of the decade, but remaining popular with BMX riders and more aggressive mountain bike disciplines such as downhill riding . </P> <P> The late 1990s and early 2000s saw advances in retention and fitting systems, with cradles which adjust precisely to the rider's head, replacing the old system of varying thickness pads . This resulted in the back of the head being less covered by the helmet, although more recent designs have largely addressed this . </P> <P> Since more advanced helmets began being used in the Tour de France, carbon fiber inserts are often used to increase strength and protection of the helmet . The Giro Atmos and Ionos, as well as the Bell Alchera, were among the first to use carbon fiber . </P> <P> Some modern road and track racing bicycle helmets have a long tapering back end for streamlining . This type of helmet is mainly dedicated to time trial racing as they lack significant ventilation, making them uncomfortable for long races . </P>

When did tour de france start wearing helmets