wouldn't a tandem have a good power to frontal area ratio?


Considering that you have 2 people pedaling with the air resistance of one person I'd say a tandem should be able to go a few mph faster than a roadie.

That is true. But you oversimplified it a little bit. Frontal area is just for rough drag calculations on simple shapes (e.g. box shapes, beams, ...). As soon as you have more complicated shapes drag calculation is quite more complex.

In the book 'Bicycling Science' by David Gordon Wilson drag and other topics of bicycling are explained in great detail. And if i remember correctly they state roughly a 1.5 fold increased drag versus a not quite 2 fold power of a tandem versus a single bike. Considering a tandem team that works very well together.

From a previous response to a similar question...

All things being equal except for the bike, (and despite myths to the contrary) a tandem road bike with two riders is between 30% to 50% less aerodynamic than a solo rider on a road bike. Therefore, in order for a tandem to maintain a constant speed that is as fast (or faster) than a solo rider, the team must produce a net power output that is at least 30% to 50% greater than a solo rider.

Moreover, consider if you will that power production on a tandem is not necessarily linear since either one or both of the two riders on a given team may at any given time fall victim to poor form, individually or collectively. Put another way, even if you have two strong cyclists (1+1), they will lose some efficiency due to the nature of a tandem and, if they are not able to work well together, their efficiency will fall way off. So, in reality what you will often times find with a tandem is that you have two riders of different abilities who can produce variable levels of output which may or may not be as high as they are able to produce when riding alone. This is why some tandem teams who are weaker riders individually than a team comprised of two strong riders are often times as fast (or faster) than the stronger couple when both teams ride their tandems. The place where a team's combined efficiency level is most obvious is when they get to the hills where you have the same math problem with percent grade being substituted for headwind MPH and the added factor of team weight having more importance than aerodynamic drag. Less I digress...

So, to answer your question, if you have a team who can produce at least 30% to 50% more power as a team on a tandem they should be able to keep up with a solo rider. However, if a tandem team can produce a net power output above what is required to compensate for increased drag, the tandem pulls the train.

Tandems are generally 'perceived' to be faster than singles. However, depends on the tandem team, experience, bike, terrain, weather and other variables. Also, these same factors apply to the person on the single bike.
But, we'd rather be TWOgether on the tandem!

Rudy & Kay/Zonatandem

It's still all about the motor.

Start by considering who rides a tandem and why. In the majority of cases, it's people who have a long term relationship that want to bicycle together. Unless a couple is very equally matched physically, that's hard to do. The stronger rider, in spite of the best intentions, will gradually creep ahead and eventually find him or herself at the top of a hill with their partner nowhere in sight. A tandem solves that issue and you always arrive at the lunch stop at the same exact time.

The practical implication of that is that tandem teams are rarely evenly matched so to assume that a tandem will have one bike's worth of frontal area but double the power is seldom likely to be correct.

A tandem is more likely to be a love machine than a speed machine.

I knew I forgot to do something after today's ride. Now, where'd my wife/stoker go?

-Dennis