Is tandem faster? [Archive]

merlinextraligh

04-01-08, 03:37 PM

For a given average power output, a tandem will be faster on the flats than a single bike.

Take 3 riders all with the same functional threshold power. Put 2 on a tandem, and one on a single bike. On the flats, the tandem will somke the single because they have twice the watts, and less than twice the wind resistence.

This is true on flat terrain where power/frontal area is the critical ratio.

On hills, the tandem team reverts to being just equal to the single rider. This is true because the critical measure is now power/weight . So if the tandem bike weighs approximately twice the single, the tandem team will climb at the same rate of a single rider of the same power/weight ratio.

swc7916

04-01-08, 04:07 PM

I find that our tandem speed is about about equal to the average of our single-bike speeds. As for climbing: If both of the riders are strong climbers individually, then I suppose that a tandem would climb as fast as a single; in my experience, there's a reason that most tandems have a granny gear.

JanMM

04-01-08, 05:48 PM

People on tandems are always passing me. Are they generally faster than single riders because there are two of them? Or are they just faster than I am, tandem or not?

People riding tandems are a step above the riff-raff on single bikes. Or, at least they are pulled down hills by gravity in a superior manner.

specbill

04-01-08, 06:34 PM

My wife and I are in the range of average recreational riders at best. She is on the low side of the range and I'm probably middle to upper. We generally average 1 to 2 mph faster on our tandem on most of our training rides if they are a mix of flats, rollers and modest hills. However if we do a ride that is mostly hills with lots of long and /or steep climbs and fast decents then I'm faster overall on a single. For us, spending long periods of time in our granies kill our overall speed too much to make for, despite our slightly faster (than my single bike's) speed down hill.
Bill J.

Niobium Rocket

04-01-08, 07:11 PM

I can average 18mph on my solo bike on a mix of hills and flat on the San Francisco Peninsula for 50 miles. Over the same ride on the tandem with She Who Must Be Obeyed, we will average about 16.5mph. There are definitely sections where the tandem is much much faster, and others where the solo bike is faster. I am more willing to whip myself to ride faster than I am my wife. But as she gets more miles under her belt, and increases her cycling strength, I am sure that the speed gap will narrow to zero!

Ti-tillIdie

04-01-08, 07:20 PM

We just finished our first century ride on our tandem .... and everyone was asking us if tandems are faster. I think they wanted an excuse for getting dusted.

zonatandem

04-01-08, 09:27 PM

If the tandems are passing you, then they surely are faster!
Next time one passes you, jump on their wheel (draft them)!

justcrankn

04-01-08, 10:12 PM

For our team we'll pass pacelines with a diagonal tailwind, or downhill. With a diagonal headwind or hill-climbing it seems like we can't get out of our own way! It all depends on the conditions.

zzzwillzzz

04-02-08, 09:26 AM

farandaway

04-02-08, 03:40 PM

Thank you much for the info. The obvious answer is gravity, since (now that I think about it) I am always passed by these folks on the descent. Der! Why didn't I think of that?

cornucopia72

04-02-08, 04:02 PM

Thank you much for the info. The obvious answer is gravity, since (now that I think about it) I am always passed by these folks on the descent. Der! Why didn't I think of that?
gravity and aerodynamics and friction. Two ridders that cruise at X MPH on their single bikes on the flat could cruise at X+1 to X+5 MPH on the tandem. Uphill the advantage disapears and for most team being on the tandem becomes a disadvantage..... X to X-3. Downhill the advatage increases with the down grade... X+5 to X+15

farandaway

04-03-08, 01:26 PM

BTW Just curious. I know nothing of tandems...what is a stoker? And is it difficult to manouver one of those bikes? It looks really precarious. Do beginners fall a lot? I wouldn't blame you if you didn't want to bother with these silly questions, but since I have all of you here in one place, I have always wondered what it's like to ride a tandem. I don't know any tandem riders personally, but the ones who pass me seem to be nice.

TandemGeek

04-03-08, 01:35 PM

What is a stoker: The person (or persons on a tandem with three or more seats) who rides behind the individual in the first seat (aka, the Captain). The Captain is the one who does the steering, shifting and braking. In earlier times, there were courting tandems where the "captain" sat behind the stoker, which is where the etymology of the term "stoker" gets interesting.

Is it difficult to manouver one of those bikes? At first, they can be a handful as new stokers have a strong tendency to try and look around the captain to see the road ahead. These side-to-side movements by the stoker's upper body tend to make the tandem move left and right. As the stoker gains the trust of the captain these unitended wobbles usually disappear. As your skills as a team grow it becomes relatively easy to make even U-turns on your basic two-lane country road and track stands are also not difficult to master.

Do beginners fall a lot? No more so and perhaps even less than beginning solo bike riders.

I have always wondered what it's like to ride a tandem. For some, it's one of the most rewarding experiences they can have on a bicycle. For others, it's pure hell. We have enjoyed it enough to make it our only past time and recreational activity. We ride road tandems, off-road tandems, and use our vacation time to particpate in tandem rallies and tours.

jgg3

04-03-08, 01:37 PM

Of course, all tandem riders are nice, cute, fast, well-shaven, knowledgeable, etc. And we never fall. Actually, a tandem is more stable than a single. Starting and stopping are a little tricky, compared to what you are used to, but it isn't hard to do.

brewer45

04-03-08, 08:05 PM

tandems are VERY fast...
but not as fast as marsupials!

JanMM

04-03-08, 08:43 PM

The first time we rode our Tandemania Comp in the parking lot of the bike shop we felt as if we were going to fall but we didn't and we haven't.

merlinextraligh

04-03-08, 09:03 PM

The first time we rode our Tandemania Comp in the parking lot of the bike shop we felt as if we were going to fall but we didn't and we haven't.

As Captain, I figure it's my responsiblity never to dump thebike. My stoker has complete faith, and never complains doing 50mph plus on twisty mountain decents.

We crash once and that faith is gone forever.

knatchwa

04-03-08, 10:31 PM

this topic keeps getting more interesting. I have often thought about a tandem just never tried it. I did see an individual with a modified one. Remarkeable if I only had got pictures. Whatever your ride at least you ride and that is a wonderful thing.

bsut

04-03-08, 11:54 PM

Alan Scholz and John Schubert write in the racing chapter of The Tandem Scoop (http://books.google.com/books?id=LEUFAAAACAAJ&dq=the+tandem+scoop&ei=vL_1R_bhK4LIsQPznc2wAg&hl=en) (2ed 1996):
One thing that's particularly positive about tandem racing is that it rewards teamwork. Two ordinary riders who work well together can overpower two strong riders who fight each other. We've seen that in the Burley Cycling Classic, where one heavily favored team had two national-class riders, one of them sporting a silver medal from the National Time Trial Championships. The other riders all told each other, "Well, we're racing for second place this year." But the time-trial champs weren't used to riding together and finished fourth, despite their superior horsepower.

Lonnie Seachris

04-04-08, 05:46 AM

We crash once and that faith is gone forever.
We ride both road and mountain tandems. If you have never crashed while riding on single track, then you still have that to look forward to::D

TandemGeek

04-04-08, 06:18 AM

[HTML] If you have never crashed while riding on single track...

... then you probably haven't ridden technical single track or just aren't trying hard enough!

brewer45

04-04-08, 08:47 AM

As Captain, I figure it's my responsiblity never to dump thebike. My stoker has complete faith, and never complains doing 50mph plus on twisty mountain decents.

We crash once and that faith is gone forever.

Malkin and I fell a couple of times when we were learning to use clipless pedals. Mostly made us laugh. Then I crashed us by going too slowly over some nasty deep angled railroad tracks. Caught the front wheel and down we went. We both got some nasty bruises (hers worse than mine) but we got up and finished our 30 mile ride. We were shaky the next couple of times out--completely avoided tracks. We're back to good riding again. The only change is that we always walk tracks that we are unfamiliar with. Faith restored (as well as the joy of riding together).

Brewer

smiller

04-04-08, 02:22 PM

Scariest moment was running about 20 before i put look pedals on. stoker decided she wanted to adjust and just stopped pedaling, my foot came off and we nearly dumped. since then, i won't ride with out clip on pedals. did dump once.. on the bike path, caught behind slow traffic, came to a short steep section and tried to downshift... but, i had the old gripshift bar end shifters and never did seem to grasp the logic with those, so i twisted the wrong way... bad thing. we were only going about 4mph as we hit the steep section and suddenly we were in the big ring. we both clipped out on the left as we are used to, unfortunately, we were tipping to the right. i'm sure it was funny those riding with us, but i remember thinking.. this won't be good, as we slowly went over still clipped in. fortunately we were unhurt and after a short beer stop, we got back on and rode another 10 miles. she still rides with me sometimes. PS the gripshift has been in a box on my shelf since and is for sale if anyone is interested, but i wouldn't recommend it!

Jalopy Jockey

05-03-08, 06:19 PM

we are much, much slower on the tandem than on my single. i race cat 3 and masters races and place consistently and my wife doesn't ride much and has little riding experience. if i cruise at around 19 mph on my single on the tandem we cruise at 15 mph. so it's not always faster.

But what does your stoker do on the same course? I have yet to get our tandem but I know I will ride around 15 mph on my old mountain bike with slicks(which is my roadie), my son will ride around 7 for a mile or two tops, together with him on the tag a long we do 12-13. My wife will do 13 or 14 on the same course. I'd bet on a tandem she'd be faster I may be slower. If I had my 2nd best riding buddy (my wife being tops (her butt is way cuter than his;)) with me I'd be much faster. He races a class up on the trails.

Pat from CA

05-03-08, 10:47 PM

I think there is a bit of a power loss on tandems as compared to single bikes. I ride at about 19-20 mph on the single bike and around 16 on the tandem.... Now admittedly, my stoker rides a hybrid by choice...so we are probably combining about 19 and 12 or 13 in terms of individual speed...but when you take into account the wind resistance factor...we should be close to my individual speed.... I think there is some loss of power in the flex that is inevitable in a tandem... there is a lot of power going into the length of that thing!!!!

So, it's not really your same speed uphill...and super fast downhill and flat....I'll agree with super fast downhill...love it!!! but don't think uphill is the same. the flats are usually faster...definitely easier!

merlinextraligh

05-04-08, 06:57 AM

I think there is some loss of power in the flex that is inevitable in a tandem... there is a lot of power going into the length of that thing!!!!

And where is the power allegedly lost to flex going? If the frame flexes when pedaled, it has to flex back, conserving the energy.

While a stiff frame may feel faster, giving a feeling of transmitting power directly to the road, there's little to no evidence that a flexng frame is slower or a stiff frame faster. (think of Sean Kelly on the original Aluminum Vitus')

Given conservation of energy, the energy that it takes to flex the frame has to go somewhere, and I'd suggest it get's returned on the frame's rebound.

Of course there can be inefficiency in the "spring." which would manifest itself in the form of heat. However, unless your frame is smoking, any energy lost in the form of heat would be deminimis.

There's a long thread about this in the road forum. And a guy named Waterrockets makes a pretty convincing case that flexing doesn't make a bike slow, both with some engineering analysis,a nd his results on the road.

Possum Roadkill

05-04-08, 09:04 AM

Given conservation of energy, the energy that it takes to flex the frame has to go somewhere, and I'd suggest it get's returned on the frame's rebound.
I've heard this argument several times before, only it seems to have been established by flexy frame manufactures. Stick a metal tube in a vice and flex it back and fourth in a vice for an hour and try to convince me that it didn't cost you any energy to do it. The flex probably causes a minimal amount of power loss however I would never want to ride a flexy frame due to other issues such as deraileur rub due to the flex. This is just my opinion of it and it's only based on my own personal experiences. You're not likely to convince me otherwise. I have ridden on a flexy bike up some steep hills and to me it feels like part of the flexing back has to be happening after you've switched force to the other pedal. However, it is interesting that the industry has moved towards making stiffer frames at least as far as lateral stiffness is concerned when a more compliant frame is clearly more comfortable to ride due to its ability smooth out the road bumps.

However, I would argue that tandems are in fact not flexy, but actually stiff in comparison to singles where it really matters. If you look at the tubing on most higher quality modern tandems, it is quite thick in diameter. Tandems can flex due to the length of the bike and from the two riders being a bit out of sync while climbing, for example, but flex from pedaling would not be any more than on a single and might actually be less since the added comfort of being on a bike that rides like a limo due to its length can use stiffer tubing without losing comfort.

jgg3

05-04-08, 09:06 AM

At the risk of continuing the war, using your energy to flex the frame flexes the frame; it doesn't turn into crank energy even when it flexes back. Things can certainly be too stiff, but using your energy to push springs that don't contribute to forward motion is just a waste of ergs.

Possum Roadkill

05-04-08, 09:26 AM

The arguement is that as the frame flexes back, given your positioning on the pedal, it should move the crank forward a little, however I don't think whoever came up with the theory accounted for any rebound occurring once you have moved to pedaling on the other side. Sean Kelly is my hero for riding such a flexy noodle of a frame and managing to do as well as he did on it.

merlinextraligh

05-04-08, 10:42 AM

Given conservation of energy, the energy that it takes to flex the frame has to go somewhere, and I'd suggest it get's returned on the frame's rebound.
. Stick a metal tube in a vice and flex it back and fourth in a vice for an hour and try to convince me that it didn't cost you any energy to do it. .

But as much energy as it cost you to move it, you got back in the rebound, minus the amount dissipated as heat. And the amount of heat genereated flexing a bike frame has got to be very very neglible.

merlinextraligh

05-04-08, 10:45 AM

At the risk of continuing the war, using your energy to flex the frame flexes the frame; it doesn't turn into crank energy even when it flexes back. .

But it does:

"...this phenomenon is called the hysteresis loop. As you've mentioned, it is negligible in the realm of cycling.

There is actually an argument to be made that the stiffer bike is actually slower. If you envision the power delivery to the rear wheel graphed against time, there will be power spikes during the downstrokes of your legs, and power lags during the times your legs are at bottom dead center (BDC) and top dead center (TDC).

A stiffer bike will very effectively transmit these power oscillations to the wheel, and make you speed up and slow down faster - so your velocity will be oscillating as well. Unfortunately, though, since aerodynamic drag is not linear (the power is roughly cubic), spending half of your time at 20.1 MPH and half of your time at 19.9 MPH takes more power than spending all of your time at 20.0 MPH.

The spring-i-er frame is better able to store the power of these oscillations and deliver more constant power to the rear wheels."

--------------------------------------------------------------------------------
http://bikeforums.net/showthread.php?t=257679&highlight=stiff+fast&page=3

This why steel frames feel "lively"

jgg3

05-04-08, 04:03 PM

The spring-i-er frame is better able to store the power of these oscillations and deliver more constant power to the rear wheels.

The fallacy here is that the springing doesn't go into driving the crank. A stiff frame resists side-to-side flexing, and this flexing will never get to the crank.

But send me your full-carbon frames, and I will send you steel ones I find on craig's list. If you are convinced they are better, you should be making out like a bandit.

mrfish

05-06-08, 05:25 AM

jgg3 is correct. Hysteresis plays a part, but I believe the main problem is that the cyclist's legs would need to provide a static reaction force when the frame springs back.

Imagine I start a track event and deflect the bb 1cm. If I now turn to stone in an instant, the bb will deflect back, my legs will provide a reaction force and most of the energy will go to the back wheel. However in a dynamic situation I would still be trying to pedal, so the frame springing back would simply subtract from my pedalling effort.

If you remember Chris Boardman's original hour record at Bordeaux, he did a lot of testing of equipment before the ride and ended up using a Corima sprint frame because it was extremely stiff and reasonably aero not because it was the most aerodynamic.

The effect however isn't huge on single bikes, but would be interesting to look at on tandems since the forces are larger and the beam is longer, leading to 16 times more deflection than a similar single bike (2x as the force from 2 riders is twice as big and 8x because a beam deflects with the cube of its length).

Does anyone know of reliable stiffness measurements for tandem frames?

Possum Roadkill

05-06-08, 11:58 PM

Imagine I start a track event and deflect the bb 1cm. If I now turn to stone in an instant, the bb will deflect back, my legs will provide a reaction force and most of the energy will go to the back wheel. However in a dynamic situation I would still be trying to pedal, so the frame springing back would simply subtract from my pedalling effort.
That's what I think happens too, however the tandem is a completely different situation. Like I pointed out before, it's important to consider where and why the flex is happening. A lot would depend on how well the tandem team performed together too. If the riders are fairly in sync with each other I don't think there's that much flex happening. I know when I'm climbing out of the saddle, if I am moving the same as my stoker than we climb much better. Like I pointed out previously the flex on a tandem is not in the BB area but in the length of the frame and only if the captain and the stoker are fighting for which direction they pull the bike, especially during out of the saddle climbing. This is probably why running cranks out of phase works better for some tandem teams.

cornucopia72

05-07-08, 06:45 AM

....so the frame springing back would simply subtract from my pedalling effort.

Does not make sense. Why would it substract...?

Does anyone know of reliable stiffness measurements for tandem frames?

Most tandem makers spend material and weigh to improve lateral stiffness.

coslickr

05-07-08, 09:11 AM

Possum Roadkill

05-07-08, 09:32 AM

..it also seems to depend on whether my stoker(passenger?) has decided to sit up and fix her hair, eat, text,etc....maybe i need to get a mirror, but for now i usually can clue in from the people on the side of the road pointing and laughing.

Nothing like being down and aero working yourself as hard as you can, wondering why the bike will not go faster and then you realize your stoker is making like a big parachute with their arms spread out, just enjoying the nice spring air. My last stoker had a tendency to do this.

My current stoker has realized that it's much easier to grab out of my jersey pockets so I can at least tell when she is eating. Our new tandem only has room for three water bottles, so on longer rides, I put one in my back pocket. She also finds this to be an easier reach, which works fine, only I come home from a ride and don't know where all the stuff in my pockets came from.

Ti-tillIdie

05-07-08, 09:36 AM

People riding tandems are a step above the riff-raff on single bikes. Or, at least they are pulled down hills by gravity in a superior manner.

I agree 100%, I mean just look at the evolution picture in my signature. Tandeming is the highest level of bicycle enlightenment. And once you reach that level of "being" speed becomes a non-issue.

merlinextraligh

05-07-08, 08:19 PM

ok, all of you who think the stiffer frame is measurably faster, where is the data?

With all the manufacturers trying to sell stiff bikes, there certainly should be some empirical data, and I've never seen it, or seen anyone link to it, in any of these threads discussing the topic.

However, we have substanital anecdotal data to the contrary:

1) Sean Kelly on a Vitus,

2) the "liveleness" of steel and Ti frames, which is a product of the spring effect.

3) waterrockects tearing it up on a steel frame.

Don't believe all the hype bike manufacters feed you to get you buy a new frame.