After many thousands of miles of riding over many years with different pilots of varying levels of ability, I believe the single most important factor in riding well on a tandem, is riding as one. Over short distances, around 1 km, I suspect that simply adding the power of the riders may well give a good approximation of overall performance and 2 very powerful riders will typically be faster than 2 less powerful riders. However, over longer distances, the delivery of force to the pedal by each rider arond each pedal cycle becomes increasingly important.

I don't believe 2 riders can ever pedal perfectly in synch with each other. And by that I mean deliver precisely the same force in the precisely the same direction around every single point of every pedal stroke. It follows that whenever they are not pedalling in synch as described above even for a fraction of a second, , one of the riders is tryingto accelerate the entire bike on their own. This may only be for a fraction of a second, but could occur many times throughout each pedal cycle. Over time, these differences fatigue both riders more quickly than they would fatigue as individuals and hence over all combined performance is compromised.

In my experience, the best way to reduce this affect is simply to do as much riding as you can with whoever you race with. This is probably why you and your stoker are faster than 2 otherwise potentially stronger individual riders on a tandem.

However, it is possible to simply just ride better with certain people from the outset, probably because you just happen to have very similar pedalling styles. And likewise, even if you ride with someone else a lot, it doesn't follow that you will ride well with them in a race. You just both might not be particularly well matched riders.

So anacdotally, based on my experience, this seems very clea to me. Indeed, I'm sure others would agree that sometimes you can simply feel a tandem accelerate when both riders don't necessarily put in a massive effort. You just seem to hone in to each other and it feels great, smooth, effortless in comparison. It may not last for long but that is what I try to do when riding with whoever.

I've also heard many pilots say that riding a tandem feels heavier than a solo bike. While this obviously could be directly attributed to one rider being stronger than the other, I know that I am stronger than some ofpeople who I ride with who also say the same thing and I know I have worked hard on the ride.

And I believe this is also supported by the fact that it is harder climbing on a tandem as well. Typically your cadence is slower and pedalling style tends to be more punchy and these differences potentially exaggerated.

We have also beaten other teams, even over short distances, who's combined power output on a static bike individually is significantly higher than our combined power output, and on very similar setups.

This all makes perfect sense to me although I have no scientific evidence or proof of the affect.

I'm not exactly sure how the Da Vincci independent drive chainsets work but if they do indeed allow eiher rider to pedal independently in a different gear, it woul be interesting to hear how riders using this drive train relate to any of the above. It think it is a little more complicated than this since riding together when linked in a conventional drive train may give more feedback to each rider and help improve any discrepencies in pedalling, as well as potentially reduce mechanical losses, but it still would be interesting to know.