On Mon, 23 Jan 2012 11:34:20 -0800 (PST), Gordon Babbitt
wrote:

Appreciating the pedaling efficiency of Rigida 27x1" clincher rims and
tires I fabricated some adapter brackets to mount on my low-end
mountain bike frame originally set up with direct-pull cantilever
brakes. Conversion is made by removing the 26" mountain bike wheels
and brakes from their mounting posts. By installing the horseshoe
style adapters on the existing mounting posts the brakes can be
remounted on secondary posts located higher up the adapters. Simply
install 27" road wheels with HP tire sizes up to 1 1/8" having similar
index shifting gearing geometry and readjust the brakes. Naturally,
700C rims with similar tires will have even more clearance from the
frame.
CONS are 1) having excessive brake cable housing from the "raised"
brake post height and 2) increased bike leaning when utilizing the
welded-on kick-stand with the larger diameter road wheels.
I would attach photos if I knew how.
This setup works great for my riding needs where one bike is desired
for efficiently riding around town for most of the year while still
accommodating mountain bike wheels for one week of mountain bike camp
each summer.
I'm wondering if there is a market/need for this kind of bracket?

To answer your question, I doubt that there is much market for an
adapter to use both 700C wheels and the normal 26" wheels on a MTB for
two reasons:

1. You can get 1.3" wide, high pressure, 26" tires that roll about as
well as the larger 700C 1-1/8" tires.

2. Generally bicycle people are divided into two groups - those who
just ride and leave any tinkering to their local bike shop; and those
who wouldn't think of letting the LBS near their darling. The first
group wouldn't understand the difference between 700C and 26" tires
and the second group probably would prefer to just buy another bike.

As for actual difference, I have an aluminum frame road bike with 700C
tires and a steel frame touring bike with 26 x 1.3" tires. The tourer
is heavier then the road bike, but even with that handicap it is still
only about 1 KPH slower over 100K; or 100 Miles for that matter.


--
John B.