what they're trying to describe on the rims, is the way the "rod brakes" work, the pads are connected to a horseshoe shaped piece. when the lever's pulled, the linkage pulls the horseshoe straight up, and the pads rub on the underside of the rim, not on the sides like conventional rim brakes.
the rims have to have a flat enough surface area so the pads can fit in without going into the spokes.
as far as the width, if you were thinking of doing away with the rod system altogether and using a standard sized tire, the only way to know for sure is to try it. if you tried to just measure it, you need to know the exact width of the tire you're using, and the measurement from the axle to the top of the tire. all tires have slightly different shapes and widths due to different tread patterns.
i have a Sukiri japanese bicycle that's similar, and it came with 26x1 3/8 tires. i converted it to 26x2.125 wheels, and used old "drop center" rims from the 40's, and i'm pretty sure i can modify the rod brake pads to work. my main concern is if they're too close to the spokes, they might turn in and get jammed, flipping me over the bars.
i'll post some pics when i can...
the rims have to have a flat enough surface area so the pads can fit in without going into the spokes.
as far as the width, if you were thinking of doing away with the rod system altogether and using a standard sized tire, the only way to know for sure is to try it. if you tried to just measure it, you need to know the exact width of the tire you're using, and the measurement from the axle to the top of the tire. all tires have slightly different shapes and widths due to different tread patterns.
i have a Sukiri japanese bicycle that's similar, and it came with 26x1 3/8 tires. i converted it to 26x2.125 wheels, and used old "drop center" rims from the 40's, and i'm pretty sure i can modify the rod brake pads to work. my main concern is if they're too close to the spokes, they might turn in and get jammed, flipping me over the bars.
i'll post some pics when i can...