Originally Posted by regomatic
Can we put 700 x 25, or 700 x 23 tires, on wheels that came O.E. with 700 x 28 and expect them to stay on the wheels throughout all conditions regardless of ride comfort?
I would say that, as a rule of thumb, you should be able to go up or down one size from an O.E.M. spec' tire size without getting into marginal size issues. However, to be sure, it's best to measure the inside diameter of a rim and, as others have noted, the assumption for the Bontragers Race Lite Tandem is that they are somewhere around 15mm - 17mm wide, giving them a "safe range" of 23mm to 28mm, 32mm if they are 17mm wide.
The other wild card would be initial tire/rim fit. Not all tires fit all rims as well as they should so, if upon initial installation the tire goes on to a given rim a bit too easy, a wary eye should be kept on that tire... particularly if it's a foldable model vs a wire bead tire.
Gatorskins don't seem to fall into this misfit category, and neither do the Bontrager rims. Thus, your proposed change to 700x25 Gatorskins for your Bontrager Race Lite Tandem wheels would be a good match-up.
Originally Posted by regomatic
And will they go on and off just as easily if we have to change a flat?
They should... again, noting that some tires fit rims better out of the box than some others and some foldables "stretch" more than others after they have been mounted for a while. My foldable Vredestein's (23mm or 25mm) go on tight out of the box, but become very easy to pull off after the first couple hundred miles.
Originally Posted by regomatic
Secondary question is ;will the 25's or 23's be much more effecient than the 28's?
Depends on your team weight, your road conditions, and PSI. If you have less than perfect road conditions, 28's might prove to be more efficient than rock-hard 23's. If you are a lightweight team with very smooth roads, dumping the 320g 28's for 230g foldable Gatorskins could give you a more responsive feeling bike.