> > I don't know what motivates
> > (marketing?) manufacturers to equip current road
> bikes with 172.5mm &
> longer cranks.
Back in the "good old days" most manufacturers used 170mm cranks on all of their bikes, irrespective of frame size. A 25" Le Tour with 170's is not exactly ideal unless you consider 160's appropriate for the 21" model. The current vintages of bikes are better equipped from the perspective of varying cranks, bars and stems to reflect what is most likely to suit the rider.
In general crank arm length has increased among elite
riders and this has trickled down to enthusiasts (who
choose their own crank length) and to product managers
(who choose crank lengths for the rest of the world).
Top riders use longer cranks because they have been
turning bigger gears (and going faster for it). It is
my speculation that this has happened, at least in
part, because the rider/crank interface has been
substantially improved through modern shoe/pedal
systems. These systems allow for higher pedaling
loads without increased risk of injury (or the same
loads with decreased risk, if you prefer). I'm sure
there are other aspects of training/sprots
medicine/doping that also favor the big gears. After
Armstrong's display in the Tour, we may say many
riders increasing their cadence and shortening their
cranks. However, I'd bet that even little Lance
(5'9"-ish?) at his very brisk cadence, is using at
least 172's.
> TIG technology was
> certainly available back then so what makes it
> acceptable now compared to the
> olden days? Different tubing materials
Yes
, new
> techniques, smart marketing vs
> stupid consumers?
No and no.
TIG bikes, as ugly as they are to you and me, shift
the stiffness/weight/cost balance in a favorable
direction. Eliminating the lugs lightens the bike and
makes it cheaper to construct. Or, if you wish,
allows for the use of better tubing &c. with the money
that would have been put into lugs and labor.
However, you still need skilled welders to build good
TIG-welded bikes, just as you need good brazers to
build good lugged bikes.
> GG
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