Re: Rare Bird- '37 BSA Tandem- She's a roller! Got a little work done today. I wanted to test ride the bike to make sure the Duomatic was working correctly. I only had one pair of close to matching seats so I threw them on. How did we ride these for miles at a time when we were kids? 2mm Stainless Steel Aircraft Cable brake line. Copper wire holding the brake cable in place.