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I've recently been touring with my Birdy folder, and people constantly ask me if it's hard work to tour on a folding bike. Compared to my normal sized bike (which has the same gearing, 8-speed internal hubs on both) I don't notice a big difference.

Given the same transmission, bike weight and riding position between a full size and folding bike, are folders less efficient?

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    None of those features are the same - a folder typically has smaller wheels which changes gearing required, and the geometries can be very different typically.
    – Batman
    Sep 26, 2014 at 15:24
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    Some folders are terrible, some quite good. Bike Friday bikes have been used for coast-to-coast rides across the US. Citizen bikes, OTOH, have been used to ride around the block.
    – Daniel R Hicks
    Sep 26, 2014 at 16:27

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  • But you don't have the same transmission as the wheels are part of the transmission. Smaller wheels are not as efficient - more rolling resistance. You also need to send more chain which is not as efficient.
  • You don't have the same position and lack multiple positions offered by drop bars.
  • The frame is not as rigid and absorbs pedal energy.

In the end if you don't notice a difference and like riding the bike then that is all that matters.

Some comments on rigid. A compact frame is not going to be as stiff as full size frame. A hinge is not going to be as stiff as a solid tube or welded joint. Birdy does some cool stuff to retain side to side rigidity in the way it folds on its own plane but it is still a small hinged frame.

You said touring. The second picture is a touring bike that is about the same price. I am not associated with Salsa other than I own one.

That single single top bar is going to have more side to side flex and and twist than a large triangle. With the taller handle bar stem and seat post there are also a longer levers to exert flex. That flex is not recovered as pedal energy - at the bottom of the stroke the flex comes out and it does not go back into the chain. The rear triangle is clearly going to be more rigid than a single hinge.

Birdy is cool bike. I am not putting it down. You asked if a folder was as efficient. A strong rider on a Birdy could hold with me on my Vaya but I am in my 50s.

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    Some high-end folders like the Moulton are quite comparable to full sized bicycles. With a hefty price tag attached, though!
    – Carel
    Sep 27, 2014 at 15:54
  • @Carel I am just responding to the question as stated. "Are folders less efficient." A folder is going to be less rigid then the same design not folding. Especially in horizontal flex that absorbs pedal energy. Not a foldable but a bike like the Salsa Vaya Travel is going to be more efficient than a lot cheaper fixed bikes. But it would not be more efficient than a fixed version of itself.
    – paparazzo
    Sep 27, 2014 at 17:28
  • @Blam Good point regarding frame flex. Many folders have a frame hinge between the steering tube and seat post which could increase flex. I had a Dahon folder in the past, and it would creak at the hinge when cycling. The Birdy, and some other folders, don't have a frame hinge, and certainly feel solid to ride, but the effect could be subtle. On the whole, the question pertains to folders in general, your point is a good one. On another point, some folders have drop handlebars (e.g. the Moulton). I've also seen drop handlebars used on a Birdy.
    – FredL
    Sep 28, 2014 at 16:16
  • Alex Moulton says in this video that it is not the size of the wheels but the inflation pressure of the tires which is "the thing that really dominated rolling resistance". vimeo.com/… The quote is found shortly before the 2:00 minute mark.
    – Tᴚoɯɐuo
    Nov 22, 2018 at 17:05
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The factors that affect bike efficiency are:

  • Weight

  • Mechanical power train Losses

  • Aerodynamic Drag

  • Rolling resistance

For a touring bike, the difference between a folding and regular bike are all lost in the noise. Smaller wheels tend to have higher rolling resistance and the bike might be a bit heavier, but for touring it just doesn't matter that much.

I think what is happening is that people remember the terrible heavy small wheeled bikes they had as kids. ( Why we give 50lb people 30lb bikes is a mystery..) They associate the relative amount of work those bikes required with your "small" wheeled bike. And yes, if a folding bike was 50% or more of your body weight it would be a lot harder to tour with.

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  • You omit geometry, which affects both rider comfort and bike stability, both of which are major factors in fatigue. This is where many folders (such as Citizens) fall way short.
    – Daniel R Hicks
    Sep 26, 2014 at 20:52
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    But that's not the question. From the OP --Given the same transmission, bike weight and riding position been a full size and folding bike, are folders less efficient?--
    – Fred the Magic Wonder Dog
    Sep 26, 2014 at 22:06
  • I've often wondered if smaller wheels are less efficient, and you mention the higher rolling resistance with them. Does this extra resistance occur at the hub due to the higher number of revolutions compared to a larger wheel? The resistance between the road and the tyre must be the same for both larger and smaller wheels (assuming the same tyre size).
    – FredL
    Sep 27, 2014 at 8:23
  • @FredL the increased of resistance is caused where the rubber meets the road. The larger wheel isn't impacted as much by the road imperfections. Think golf ball vs soccer ball on the grass. The larger wheels also have more mass thus higher momentum. Now, hubs are pretty universal so in this case they would be the same. However if there is a drag in the hub bearings, the smaller wheel will loose over distance traveled, not by revolutions (ignoring the momentum of the larger wheel).
    – BPugh
    Sep 27, 2014 at 13:50
  • @BPugh Good analogy with the gold ball vs soccer ball - makes sense.
    – FredL
    Sep 27, 2014 at 14:58

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