What singles don't have much of, and tandems do, is rear or stoker steer. With a living and significant (can be greater the captain) stoker weight any shifting about of uneven pull on the bars by the stoker will induce a steering torque. I've had tandems veer off to one side with no warning before when the stoker reached for their water as example.


Some brands want to reduce this best possible and so use a long trail geometry. Others want a more lively feel and use less trail. When I worked for Allstar Bike Shop (Raleigh, NC) we sold Santana, CoMotion, Burley, Calfee and had the odd da Vinci, Cannondale, Lightspeed and others go through our hands. We joked that the first tandem a team got was often a Santana (or Burley, budget dependent). A pre sold name and easy handling for a new team. But that team's second tandem a few seasons later was more often a CoMotion or Calfee with their quicker reaction to steering inputs. That more experienced (and better balanced/stable the riders were) the team the less they likes the dead/stable feel of the long trail geometry.


Think of the rear weight bias of a loaded touring bike and their commonly used long trail as a reference VS the short trail of a more front weighted Rando bike.


I just looked up the design blueprints for our CoMotion. It has a 73* HA, 680 diameter tires and about 51mm of trail. When I was working with CoMotion I never asked for any specific geometry but did request a quick handling feel. Our custom Speedster felt more like my singles (which all have a bit more then 60mm of trail).


The other aspect I learned was that it's hard to make a tandem frame too torsionally stiff and too long in the stoker's compartment or chain stays. Sure many will diss long rear ends, basing their opinion usually on a single bike's standard. But being able to cross chain and having that rear tire contact with the ground well behind the stoker's butt goes a long ways to make real riding more enjoyable.


I set up the captain's BB at it's lowest (assuming it's an eccentric for timing chain adjustment) so if any pedal strikes ground it's the captain's. With such a long wheel base any small rise (speed bump or driveway ramping) will get lost between the tires and pedal strike happens when not expecting it easily. If the team is good and their stopping method keeps the stoker clipped in then the rear BB can be fairly high and the taller stand over is far less an issue then the stoker's single has. My partner and I don't use this method (sometimes called "the proper method" by those who don't have a broad view of how relationships work...) so her stand over is important. This is best figured out before spending a lot of time or money.


And it is this last point that I will restate. You are a team, not a captain with a passenger. Whatever it takes to make the stoker happier will make the shared experience better. My first tandem was a Motobecane way back when. I bought it used from a pair of club members who never saw the same things when riding on it. he would wonder why they were so slow going down hills and she would complain at how fast they were going as she was pulling on the exposed brake cable to slow down. The old saying is that where ever the relationship is going it will get there faster on a tandem, for better or not... They were divorced a few years later. Andy