I've got a 26" Townie i3. I love the relaxed position etc but it doesn't have disk breaks and has a 120mm rear dropout. It currently has an old crystalyte 408 front hub. The only way to add a decent rear brake would be a sturmey archer rear drum. It needs new wheels anyway at this point. So buy a couple new wheels or buy a new bike that has a disk brake setup and move to a newer motor?