Hi Mechanics.

I have two different sets of wheels--Rolf Vectors and Mavic Cosmics--from about 1999. I notice that when I'm coasting downhill on a group ride, I coast a fair bit slower than pretty much everybody on the ride. I know my wheels are older than everyone else's, and were made with what would now be considered "inferior" materials (and probably design as well), but are my wheels' slowness due to the hubs, the spokes/rims, or the tires?

When I spin them by hand, both sets of wheels seem to go smoothly and for a long time. When I do a "coasting test," the Rolf Vectors (with "go fast" Continental tires) roll much farther than the Mavics (with "anti-flat" Specialized Armadillo tires). I can clearly feel the difference when I'm riding one bike with one set of wheels and then switch the wheels and continue my ride. It's like the difference between road and mtb tires.

I'm considering getting a new set of wheels anyway, but is putting the same (new) tires on both wheelsets and then redoing the rolling test the easiest and clearest way to find out which of my current wheelsets is faster?

Thank you.