I'm the default mechanic for a large-ish 600mile family ride every summer (22 years running). Folks are always trying to figure out new bike options for their family for the trip. I've had a standing offer that anyone who finds a decent freebie 10 speed can drop it off and I'll get it trip-worthy. I've mixed/matched just about everything including 27" and 700c wheels --all just depending on what's laying around. None of them are ever really worth the time and $$, but it gets an old bike and a young person matched up and riding. And that's cool.