Originally Posted by
TandemGeek
......... Now days, you have folks like Co-Motion and Calfee designing their tandems around these single-bike-based fork designs to fine tune the handling so that there aren't any trade-offs and any good custom builder who has spec'd a composite fork for a customer's tandem has likely done the same when setting the head tube angle and adjusting front bottom bracket placement for toe-overlap considerations. ......
Lots of good information in TandemGeeks's post. The head tube angle calculation is very useful. I think however that he may be overstating the builders design care and expertise when building tandems with carbon forks. Using CoMotion (a fine company) as an example, when they built tandems with steel forks they used a 73 degree head tube angle and a 50mm rake fork. When using carbon forks, Alpha Q, Woundup Composites, or now Enve they still use the 73 degree head tube angle. Some of these forks have different rakes. It appears to me that many tandem builders like the 73 degree head tube angle regardless of the fork used. This is not a terrible thing and I suspect that there are production reasons for taking this approach. It appears many builders don't sweat a few degrees of fork rake on there production non-custom geometry frames with carbon forks.
One exception for good or bad is Santana which believes in 55mm rake and 1.25 steering tube forks. They sources their own carbon forks and specify 55mm on the carbon ones to match the 55mm on the steel ones that they make in house.