We've had this discussion several time before. I'm in the camp which maintains that the only weight which matters much is the weight of the rims and tires, which have a large moment arm around the center of rotation (the hub axle). The weight of the frame and rider act at the center of rotation and have essentially no moment arm at all. The weight of the bike does contribute a bit to the rolling friction on the tires, but the force required to overcome rolling friction is trivial compared to that required to overcome the aerodynamic drag on the rider's body. In short, you expend lees energy drafting behind someone on a 25 lb bike than riding in the wind on a 15 lb bike.
Weight matters when climbing, as energy must be expended to lift the weight against gravity. It also matters when accelerating (force = mass x acceleration). But bicycle road racing, unlike automobile road racing, does not involve frequent hard accelerations. Theoretically, a very light bike would be beneficial in field sprints in a road race, in track sprinting, and in criteriums, but the first two are typically the the domain of large, muscular riders, who need a stiff frame to resist flexing more than a superlight frame. Criterium specialists are also concerned with frame stiffness. So mountain stages are about the only place where a superlight frame may make real sense, which may be why the top pro teams for decades have tended to use superlight frames in just such stages.
Regards,
Jerry Moos
Houston, TX
> I am wondering why racing bikes go through "lightweight" phases,
> usually followed by phases of "we don't care about weight."
>
> I don't know much about the 1950s, except that bikes don't seem to
> have been very light or even built with weight as a foremost
> consideration. Durability, Q factor and other things seem to have
> influenced component choice more than light weight (steel cottered
> cranks vs. aluminum ones, steel stems, etc.)
>
> 1960/70s saw an increased interest in light weight, but maybe not
> among pro racers. Most of them rode sturdy NR. I realize I have
> visions of Merckx' drilled bars on the hour record bike, and Ocana on
> a ti frame, but for the most part, it seems racers were rather
> unconcerned by weight.
>
> 1980s: LeMond won the world championships on 36-hole wheels, which
> now fellow randonneurs (!), who have no support cars, say are too
> heavy to go fast! Yes, Greg used TVT carbon frames, too. But for most
> other riders, bikes actually were heavier than in the 70s - witness
> Columbus Max tubing and such stuff.
>
> 1990s: With "innovative" bike companies becoming more active in
> sponsoring pro racing (Cannondale and Trek come to mind, but Bianchi,
> too), they wanted to showcase lightweight bikes, since they couldn't
> compete on "mystique" and craftsmanship. So the bikes are getting
> lighter. Would Eddy have won more decisively on a Trek? Would Lance
> be slower on a Colnago NR bike? Who knows?
>
> Any thoughts?
> --
> Jan Heine, Seattle
> Editor/Publisher
> Vintage Bicycle Quarterly
> http://www.mindspring.com/