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A lot of effort and resources go into making cycling shoes stiff, presumably to keep the foot in a suitable shape and spread the force across the sole.

It seems like it would be possible to achieve a similar effect by making pedals long enough to support the entire foot, with or without a retention system. However I'm not aware of the existence of any pedals like that, so I suppose there must be strong disadvantages to them that I haven't thought about.

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    Whose foot would one model such a pedal on? You would end up creating a pedal that fitted only individuals with certain size feet, or you would be forced to manufacture pedals in multiple sizes.
    – Deleted User
    Commented Jun 23, 2015 at 22:41
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    With the foot off the pedal, the pedal would strike the ground and cause a spill. Probably about six inches is the longest practical pedal on a standard upright bike.
    – Daniel R Hicks
    Commented Jun 24, 2015 at 0:08
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    It should be noted that, for the normal healthy human foot, there is no need for the pedal to support more than the front third or so, as the arch of the foot places all the force on the front third.
    – Daniel R Hicks
    Commented Jun 24, 2015 at 3:10
  • The longest pedals I've yet seen are the ones I use: MKS Lambdas. (There are also knockoffs available.) Nine inches long at the longest point. I haven't had a ground scrape yet, but this is a touring-style bike with a long wheelbase, so it doesn't lean much.
    – D.Salo
    Commented Jun 25, 2015 at 2:23

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I'd wager the two biggest reasons you don't see foot-sized pedals are the increased rotational weight, and the difficulty you would have catching the pedal with your foot before it struck the ground or the front tire. I'm sure someone tried this once and promptly scrapped the idea after the foot-sized pedal struck something.

Pedals need to be stiff and durable, which is fine. But if pedals had to be stiff and durable and large, they would probably end up being heavy, so it makes sense that most pedals you see are small and compact. Shoes already do a great job of interfacing with and conforming to your feet, and it's easy enough to make the sole stiff with plastic, fiberglass, and carbon fiber. All of these factors combined explain why we have small pedals.

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    The rotational weight is a red herring -- the weight (using typical bike materials) would not measurably affect performance. But people would think it did, which is another reason why the idea wouldn't fly,
    – Daniel R Hicks
    Commented Jun 24, 2015 at 3:08
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One big difference is where the force is applied. In a conventional pedal, you press down using the ball of you foot. In a foot-long pedal you would have to center the axle so the pedal stays level, but that would mean that the force would be applied by the middle of your foot. You would be losing the power and flexibility that your ankle can bring.

Being clipped in the pedal also has many power and security advantages. Does your footlong pedal in your scenario has a way of being clipped ? In that case you still need strong shoes with a sole, so why have that big of a pedal when you can have a single smaller point of contact ?

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  • I considered the scenarios of clipless, to-clipped and plain platform foot-long pedals. I suppose with clipless particularly even if the pedal is big enough to fully support downward pressure the rigidity of the shoe would be needed to for pulling upwards or sideways.
    – bdsl
    Commented Jun 24, 2015 at 20:41
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You still want the axis approximately at 30% of your feet's length - that's when pedalling is most efficient. Just try to pedal with your feet's centre or back on pedal. Full-foot pedals accordingly will be asymmetric, implying they will be one sided and will tend to point to the ground with their backs when you're off-pedal making, as mentioned before they will then scrap over the ground.

Another reason shoes are stiff is efficiency: the stiffer your shoes the less they will compress each time you push onto the pedal. The energy this compression costs is proportional to how much your soles are compressed. This compression will be almost inelastic, meaning it will just heat up your shoes instead of pushing you forward. A rough estimate of the energy you lose: each half crank turn the pedals move by 34 cm down (twice the crank length), but due to compression of the sole, your feet move 34 cm + d. d=5 mm gives only 1.5% loss that should be hardly noticeable, it definitely feels like more. My argument might miss something or ergonomics is involved, which is hard to put into equations.

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    Another reason the shoes are so stiff is to keep them from breaking in half. Back in the 70s there were shoes made with a stiff toe but relatively flexible between the toe and the heel. When walking on these the shoes would flex at the point where the toe stiffener ended, resulting in a crack at that point. Making the entire shoe uniformly stiff prevents this problem.
    – Daniel R Hicks
    Commented Jun 25, 2015 at 0:57
  • With platform pedals shoes with very thin and flexible soles work well, for the same reason.
    – ojs
    Commented May 17, 2016 at 21:08

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