I've put 700c wheels on my 720, and it increased the canti's leverage somewhat, though not as much as if I had used a norrower rim than the 25mm wide Mod4's.
The pad dive angle increases with narrower rims and also with smaller diameter rims, so the wider (25mm vs. 22mm) rims I used minimized this. 700c Rhynolite rims are similarly very wide.
As far as keeping things original, unless the hubs remain original, what's the point? I would first consider what style of tire is desired, then decide between 27 and 700c. Certain (27") traditional touring tires should be around for many years.
Most of the new 27" stuff has already been clearanced off, leaving Ebay, swaps and thrift store bikes as rim donors, and a surprisingly good number of remaining sources of high-quality 27" touring tires.
David Snyder
Auburn, CA
> Hi Folks,
>
> I dug up a beatup 83 Trek 620 (Serial 108438). It has an incorrect front
> wheel (old steel raleigh maybe?) and has a functioning (for now) Malliard
> Helicomatic 6 speed.
>
> I kinda like the Malliards, but I realize there are no parts to speak of
> available, & that they don't have a great reputation for reliability.
>
> Obviously I have to replace the front wheel, & was thinking of doing the
> back as well. Would it be sacrilege to replace them with 700c? Perhaps
> even go with a 7 speed (probably freewheel since 7 speed cassettes seem a
> little thin on the ground).
>
> Did Trek sell bikes in Europe in that vintage? If so did they use 700c
> there?
> I did poke 'round the vintage-trek site but couldn't find any real
> reference
> to it.
>
> Jon Tromp
> Seattleish, WA