From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Sloping frame for road bike?
Date: 25 May 2000 00:37:33 GMT

anonymous writes again:

> Lowering the top tube raises the CG? Strange.

Not so if the hardware that reaches the bars and saddle becomes
heavier to make up for the short frame... which it must if there
is a significant difference in frame height.

> What about with an upward sloping stem, reducing head and sterring
> column.  Surely that saves weight?

Surely what?  What is the pursuit here again?  Take it to an obvious
level by using a BMX frame and the required seat post and stem to get
the right fit formerly achieved by a conventional fit frame.  That is
distinctly heavier than a proper fit frame.

> Why go up then along as is the tradition. (Always to me)

There are aesthetic and practical reasons for horizontal top tubes and
stem extensions.  I think you'll find that they have their good
reasons if you ride a bit.  It used to be easy to define a frame in
height of the seat tube from the BB and length of top tube.  This no
longer holds true with the variety of up and down sloped top tubes,
many of which are smoke screens for builders who cannot make a top
tube horizontal.

> Have you measured the increased weight you speak of.  Seat tube will
> be shorter as will stays.  There are some pretty light seat tubes
> around now.  What about a carbon fibre one.  I thought Jaja's bike
> looked just the ticket.

Go ahead and get one but don't tell me it's for any technical
advantage.  These guys get paid to ride this stuff and do so as long
as it doesn't get in their way.  Typically in a hill climb, in stage
races, only the team leaders times have any value while the others
must ride to stay in the race.  They have no team function in such an
event so most of the domestiques ride bicycles and wheels that no
competitive rider would touch.  Meanwhile the bicycling public goes
gaga over the heavy aerodynamic wheels and goofy bikes they see going
up the hill.  Run right out and get one.  It's just like "racing"
glasses, expensive pieces of plastic foil that makes riders look like
aliens.

Jobst Brandt      <jbrandt@hpl.hp.com>