I was mistaken when I deemed my child carrying bike perfected. The Bobike Mini is indeed the best child seat you'll find for sub 33 lb children, but I squeezed in some Schwalbe Fat Frank tires the other day and well . . . I'll just have to gush below.
In "Historic" downtown Wilmington half the steets are brick and the other half are terrible. Okay, I exaggerate. About a third of the streets are brick. Seven twelfths are terrible, one twelfth is smooth. Does that add up to one? Downtown Wilmington is built along the Cape Fear River. Water, Front, 2nd, 3rd, etc. run parallel to the river. Water is mostly brick. The streets which run perpendicular to the river are mostly brick. 3rd street is smooth. 2nd is smooth for six block. Everything else isn't brick but is very bumpy.
I'm not complaining. My gut feeling is that really bad roads act as traffic calming devices.
Back to the tires. In rough terrain these excel, but even on the smooth streets of mid-town the tires are fast and unbelievably comfortable.
The tires float over brick and cobblestone. Improvised unpaved lines become as smooth as chipseal. They aren't just huge tires. They are very nice huge tires. Thin, supple sidewalls. Just enough tread.
Me and my son equal a 200 lb rider. I've been using 25 psi in the back and 20 in the front. The bike rides like a dream. You have to try them to understand. I have e-mailed Schwalbe begging for a 650B or 650A version. It won't happen. Like the Gran Bois Hetre and Cypres, these are tires worth of designing an entire bike around. In fact, Frank Patitz, the tires' namesake, did just that.
Schwalbe Fat Frank tires are (unfortunately) only available in 26" (559-60 ISO) diameter. They are available in black and cream. $40 each. The Big Apple, which is similar to the Fat Frank, is available in a wider variety of sizes. Black only. $40 for 26" and 700C versions, less for smaller wheel diameters.