Hywel & Ros wrote:

Anyone care to suggest why modern bikes tend to have sloping top-tubes ?
I more-or-less understand the engineering merit of butted tubes, and
perhaps conical tubes, but I can't understand the merit of a sloping
top-tube. Isn't this effectively, just a smaller frame, with a great long
seat tube.

Not really, because the steering tube isn't shortened. The smaller rear
triangle is meant to be stiffer and the sloped top tube is a bit shorter
and therefore lighter. But the longer seat tube will cancel at least part
of these effects, so I think in these respects any differences between
designs will be negligible.

Higher standover clearance is more noticeable, and I find it a definite
advantage.

But significantly to manufacturers, the compact frame design allows for more
flexibility in seat post length and so they seized the opportunity to save
money by reducing the number of available frame sizes.

And as a boon to marketing departments, introducing the "modern" sloped
design put replacement pressure on owners of "outdated" traditional bikes.


I'm not saying it's wrong, just I don't see why

Also, why 26" wheels rather than 700c ? According to the Thorn website
there's less rolling resistance, but more air resistance.

I would have thought it's the other way around. But anyway, any effects due
to a rather small difference in wheel size are negligible compared to
factors like tyre width, pressure, and tread pattern.


I have a Thorn bike with both these features and I'm very happy with it -
and it seems easier to pedal than my old 700c / 27" bike though that was
old and lower-quality, albeit not much heavier, and OK for what it was.

All kinds of things other than wheel size could explain that better: higher
tyre pressure, better seating position, lower handlebars (and therefore
less drag), a cleaner chain, ... .

Andy