"Hywel & Ros" writes:

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.

Better stand-over height.

Isn't
this effectively, just a smaller frame, with a great long seat tube.

When I was a lad we were advised not to have our saddles up too far
because of flex in the seatpost, and, consequently, to get the biggest
sized frames we could manage. Seatposts are obviously stronger these
days.

In an emergency stop, falling off your saddle on to the top tube is
**sore**.

Also, why 26" wheels rather than 700c ? According to the Thorn website
there's less rolling resistance, but more air resistance. I don't doubt it,
but why less rolling resistance ?

I think that must be bollox [tm]. Rolling resistance is a function of
the size of the contact patch which is a function of the pressure in
the tyres. The air resistance thing is much more complex, but the
difference between a 26" and a 27" tyre really can't be much. Bigger
wheels cope better with irregular surfaces, and it's notable that some
mountain bike designers are now experimenting with 28" wheels,
which, interestingly, is exactly what I had on my very first bike.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/

do not sail on uphill water
- Bill Lee