No idea what Bontrager Racelite tandem wheels look like, but if they're narrower than Ksyriums, I see no reason not to try. I regularly run 23's on my Ksyrium rear wheel (can't afford the matching front!). As it says in Sutherland's bike mechanic's guide, "One measurement is worth a thousand expert opinions."

Same thing goes for tire efficiency. I would think the 23's would be more "efficient" than 28's, but maybe there are different dynamics working on a tandem as opposed to a single that I don't know about? For now, I would use the 23's until someone can show me that 25's or 28's are more efficient. After all, we ran 21's on singles until they figured out that 23's were more "efficient," or at least gave a better ride without significant loss of efficiency.

- L.