Not all FSA tandem cranksets are compatible with a Santana, noting that Santana builds their tandems using a 73mm wide bottom bracket (BB) spec. vs. the more common 68mm width used by most other tandem builders.
Let's talk about the 73mm spec first, as that's pretty straight forward: Santana spec's the wider BB for two reasons. The first is to allow for the use of large diameter, un-dimpled chainstays and the second obviously helps a bit with regard to moving the chainline out 2.5mm to help off-set the 160mm rear spacing. Santana also added a special "far-out" front derailleur mounting bracket to their tandems around 1999 for use with a quill type front derailleur that also helps to off-set the chainline by moving the front derailleur another 5mm. FSA now offers a similar deal for tandems.
As for FSA cranks, purportedly there some FSA tandem cross-over cranksets out there that can be installed on either 68mm or 73mm wide BBs. However, not "all" FSA tandem crossover cranks were produced this way. On the sets that can go both ways, there is an extra set of 2.5mm spacers that are installed between the bearings and cranks on 68mm BB's, and simply not used with 73mm BB's. This same type of arrangement is used on certain models of FSA's road and MTB cranks as well. Therefore, before buying a set of FSA tandem cranks for use on a Santana you'd want to have the seller verify that the cranks they're selling are compatible with both 68mm and 73mm bottom brackets.
Last edited by TandemGeek; 03-15-11 at 12:56 PM.