Originally Posted by
seypat
As a follow up post, on another thread I used this example about the added muscle. Go out, do yourself a nice 30-40 mile varied terrain route and note your results. Now clone yourself and get a tandem. You and your clone mount the tandem then do the same route. The tandem version will have totally different results than yourself. Despite being twice as heavy, the tandem version will be significantly faster in the flats. But on the hills and climbs(because of the weight) will struggle and be searching for more gears.
The hypothetical tandem should do roughly equally well on the hills assuming the weight of a tandem is roughly twice that of a road bike (I'm not sure how much tandems weigh tbh, but the 2 riders dominate the weight of the system). You'll have the same power / weight ratio (big factor) and slightly lower air resistance (small factor).
The reason the tandem will do better on the flats isn't just the extra power -- the stoker effectively drafts the captain, making the total air resistance much less than the total from 2 separate riders. IE, the two riders have to produce less power to generate the same speed on the tandem as they would if they were on separate bikes.