Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Pedal Stack Height

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Old 03-04-05, 04:47 PM
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53-11_alltheway
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I found some interesting information on pedal stack height and it's relationship to pedal biomechanics.

Apparently reducing stack height makes it easier to apply force at the top of the pedal stroke, but slows down pedal speed at the bottom of the stroke (I'm guessing by reducing the total length of the leg)

However, I notice the same effect whenever I raise my saddle. I can apply more force at the top of the pedal stroke, but I lose a little bit of my "spin" at the bottom.

I've always thought reducing stack height was beneficial for performance, but I just wonder if the reverse is true now. Maybe using a pedal system with higher stack height would let me use a higher saddle position while increasing the length of my leg at the bottom of the pedal stroke.

Comments please.

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Old 03-04-05, 05:03 PM
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Originally Posted by 53-11_alltheway
I found some interesting information on pedal stack height and it's relationship to pedal biomechanics.

Apparently reducing stack height makes it easier to apply force at the top of the pedal stroke, but slows down pedal speed at the bottom of the stroke (I'm guessing by reducing the total length of the leg)

However, I notice the same effect whenever I raise my saddle. I can apply more force at the top of the pedal stroke, but I lose a little bit of my "spin" at the bottom.

I've always thought reducing stack height was beneficial for performance, but I just wonder if the reverse is true now. Maybe using a pedal system with higher stack height would let me use a higher saddle position while increasing the length of my leg at the bottom of the pedal stroke.

Comments please.
Don't know about stack height, but I'm glad to see you're back, 53. I missed you.
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Old 03-04-05, 05:15 PM
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53-11_alltheway
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Originally Posted by Chorus_Girl
Don't know about stack height, but I'm glad to see you're back, 53. I missed you.
LOL.....Yeah I had a good link to this, but I can't find the article anymore. The url isn't on the top of the pages I printed out.
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Old 07-11-05, 05:33 AM
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samp02
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Can anyone put into easy to understand what stck height does to your position and pedal stroke???
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Old 07-11-05, 05:52 AM
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I have noticed something similar. I had these shoes that had like a really really thick sole. I would notice a major difference between wearing those shoes and any of the other shoes. I am sure if one wanted to nerd out one could put the force vectors in and come up with a reason that explains both the speed up and the slow down. I never noticed a slow down but I did notice the increase.
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Old 07-11-05, 05:56 AM
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Originally Posted by TexasGuy
I have noticed something similar. I had these shoes that had like a really really thick sole. I would notice a major difference between wearing those shoes and any of the other shoes. I am sure if one wanted to nerd out one could put the force vectors in and come up with a reason that explains both the speed up and the slow down. I never noticed a slow down but I did notice the increase.
Time markets low stack height as an advantage (info on Time website). Also if the stack height difference was great enough it might have a tiny effect on the hip angle.

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Old 11-05-05, 04:13 PM
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Lower stack heights make the pedal stroke more effecient, particulary through the top and the bottom of the stroke. The reason for this, is simply because the feet are closer to the axles, so the force you generate is more directly transferred to the axles. For instance, imagine putting a 6 inch spacer between your shoe and the pedal. Then imagine what would happen when you are pushing straight forward, coming through the top of the pedal stroke. The force would be way above, and not in line with the pedal axle, so the force would cause the pedal to rotate forward around the pedal axle, as opposed to the force going into the axle, to power the cranks. The same would be true when pulling back at the 6 oclock position, except the pedal would rotate backwards, instead of forward, with very little, if any force going into the cranks. And even in the 3 oclock position, where you're pushing down towards the axle, even the slightest misalignment of the direction of the force towards the axle, would cause the pedal to want to rotate forward, or backwards, around the axle, (known as pedal rocking) which would make it extremely difficult to get any significant power into the cranks. So the closer the force is brought in line with the axle, which a lower stack height does better in all situations, the better the energy transfer will be, with less pedal rocking. Of course in the real world, your feet are a lot closer to the axles than 6 inches, but the principals are the same. And with taller stack heights, it's necessary to "ankle" (raise, or drop the heels) to get the force more in line with the axle, which wastes some energy.

I switched from Looks, (one of the worst stack heights out there), to Coombe Pros (one of the best) about a year ago, and it's the most noticable improvement I've ever made to my bike. The lower stack height knocked almost a full minute off of a 15 mile time trial course that I ride regularly. That's more than I got from my very expensive aero wheels, so low stack height pedals are a great way to improve performance.
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