The rule of thumb is that there is a 20 to 30% reduction in power required when one drafts another bicycle. But what about a tandem? On occasion, I have drafted a tandem on my road bike and the benefit seemed really good. On a recent ride, I had the opportunity to draft a tandem while on my road bike and made some mental notations about power output (I have a power meter).

Climbing a 2% grade, I was at 150 watts (1.94 w/kg) and off their wheel by several bike lengths. For a 310 pound team (estimate) that puts them at 273 watts combined assuming the same power to weight ratio as me. Riding and chatting side by side, we were on a slight descent and I was 150 to 170 watts. From the side by side position I dropped behind and for the same speed by power dropped to 70 to 80 watts. So instead of the 20 to 30% reduction in power, I was seeing more like 40 to 50%.

We come to a downhill section 3 to 5% and my friends decide to ride me off their wheel. Tucked in behind required very little power. I backed off to create a gap and my power went up to 300 watts. I stayed off their wheel to confirm the number and then bridged back - 600 watts. We started another 2 to 3% climb and I was next to them at 150 to 170 watts. I said boy that was fun. I could have easily rode away as they were now working hard climbing.

To potentially put me in trouble on a climb, a 310 pound team would have to make 550 watts for at least 5 minutes. This assumes I am on their wheel getting some drafting benefit.

We really did not need a power meter to confirm what all tandem riders know by simple observation and experience that riding with others on road bikes puts the tandem at a significant tactical disadvantage but I thought some may find this interesting and it is a nice diversion from low spoke count wheel failures.

Any other drafting experience or observations?

Group riding with tandems is pretty cool. We like it. Rollers are especially fun. Singles make a hash of it. We either have to wait for them or they have to be really aggressive wheel suckers, which isn't that much fun for us when the tandems are working hard together. If we can get rid of the Klingon they're usually gone, at least until we come to a long climb. Not too many singles are interested in the 600 watts thing. The trick is to be nonchalant, then accelerate hard just past the crest. That usually catches them by surprise. Once they're 20' back . . . If they can come back up, we usually don't mind, because that means they are at least competent and might stay out of our way.

I give a good draft whether I'm on my single or on the tandem. The faster the speed or the headwind the greater the advantage from drafting. Before I ever owned or even rode a tandem I did a 600km (386 miles) ride drafting a small (5 bikes) peleton of tandems. We finished the first 200kms(118miles) in 4hrs 45mins. We were going 30+ in the flats and I was just hanging on in the back saying to myself "I shouldn't be doing this, I shouldn't be doing this" but it was hang on the back at 30 or drop off and go 22 by myself. So, I hung on. I'm so used to people drafting me that it doesn't bother me when they are there. I pretty much just ignore them.

A counter-case: during the NWTR we worked a bit to catch two tandems in a draft. Unfortunately, the second tandem was captained by a strong rider (meaning much younger than we are) with his 6 y/o daughter on the back. Let me say unequivocally that there is almost no draft in that situation - probably almost as bad as being 3 feet behind a single. We had earlier ridden alongside the gent and his daughter: very nice folks and they were having a blast. We also got passed by two kids on a tandem. At the next rest rest stop the parents (also on a tandem) took the captain's position on both tandems. The (young) woman and the youngest son took off like a rocket; probably not much draft there either.

On the same lines... try to draft from a recumbent with a tandem: almost not worth the effort to keep close to the wheel.
Singles love to draft from us... We open a big hole and our speed is almost constant.
We like to draft from tandems of equal of slightly better abilility. Then there is the large experinced single riders. Last is the tinny squirels that think it is fun to accelearte 3 to 5 MPH for a few hundred feet after they suck our wheel for 3 miles.

On one race I did on our tandem with the rest being singles I found there was only one way to drop them. That was to drift of the back near the top of a hill and then really go for it down the other side. You go past the bunch of singles with such a great speed difference that they can't jump on.

Yeah it kinda sucks sometimes. You give such a good draft that on a rolling road, even though you are going super fast on the downs, the drafting rider can hang on. Then when the road pitches up, they pass you...

We always do that that anyway, but I'm going to call that my strategy from now on. Only we usually start drifting back at the beginning of the hill.

In bike racing, this is called the "slingshot," and is pretty much the basis of track sprinting. When you've got two guys evenly-matched for top-end speed, the only way to beat the other is for one guy to accelerate into the dead air behind the other, and then carry that speed past him. I think this is one technique that most bike racers don't practice enough. I remember that Mike Walden and Dale Hughes were very big on this at their training camps. Most bike racers are loathe to lay off by a couple of bike lengths when the tempo picks up to sprint rollout speed. At the recent NWTR in Medford, we blasted past a much faster tandem on a descent using this technique. You do have to be a decent bike-handler, so you don't run right up the other bike's back wheel, though!

Luis

(btw, in case you're interested, the response to the slingshot is "the razor," or "keeping your opponent on the razor." So if you're the guy in front, you make sure to accelerate only to about 80-90%. Then, when the other guy comes around, you then make the real jump and keep him on your hip. If both of you have the same top speed, you win.)

We were riding our first tandem century and my first century ever, in Palm Springs. We were cruising along about mile 80 into a slight headwind. I was doing about 20 and I was starting to get tired. I told Deborah I was getting tired and was going to back it off a little and rest. A voice behind me called out "you're doing a great job up there". I looked behind me to see a string of about 20 bikes. Don't know how long they were back there because I hadn't thought to look behind for wheel suckers. Riding with a group usually finds the tandems up front. It is really difficult to paceline especially if the group is inconsistent. The bungee effect is murder.

As a predominately solo rider I would like to thank the tandem teams who have caused me to ride myself inside out to hang on to their back wheels as they "attacked" the bunch. It really sharpens up the high speed pursuit skills and endurance.
As a tandem captain I giggle like a girl when my solo friends can't keep up when we hammer down hills.

Or on the flats for 25miles @ 28+

That is approximately a 53:37 40K TT time and definitely National Champions or should be in multiple of tandem divisions.