Hi Don - I have a couple of 63cm Ramblers (one Zen, one Bantam w/S&S couplers) and I've run the following, without fenders:
- RH Snoqualmie Pass 700Cx44
- RH Hurricane Ridge 700Cx42
- Soma Cazadero 700Cx42
While all of these have plenty of room at chainstays and brakes, I do have to install the Snoqualmie Pass underinflated to get them past the brakes. I also regularly run Barlow's when I have fenders on.
Dave