i've gone to the trouble to try out mtb wheels (559mm) on an old steel frame built for 27 (630mm) wheels. i put a coaster brake rear hub on it to solve the braking problem. no front brake. so going from 622mm to 571, as you mentioned, will involve a smaller discrepancy (about 20mms) LESS than the one i tried. then i rode it around for a while.
the BB is low, but not unreasonable so. the killer for me was that the smaller front wheel induced a terrible front wheel wobble at anything above 10MPH. i was surprised.
i'm pretty sure a long reach caliper brake won't cut it. maybe a drop bolt...
i think there are front drum brake hubs too. that may be a possibility.
Last edited by hueyhoolihan; 01-28-13 at 01:20 AM.