Cycling in Alignment - Crank arm relationship

A great question from Dave in the UK came through recently regarding crank arms and their relationship to our pedaling dynamics. He asks:

All cranks are at 180 degrees. As we are human and not machines is 180 the optimum spacing? Again I was wondering if any research had been done to see if it’s not something like 170 or other such spacing.

So I immediately think of some of the technology that has come around over the years such as the independent cranks, where you can freely pedal both crank arms and essentially allow them to exist at any relationship/angle. I wonder if there is more out there on more specific spacing relationships?

@colbypearce, what has your experience and expertise taught you about this topic?

Coach Ryan

The cranks you are talking about @ryan are [confusingly named] Power Cranks. They have nothing to do with power meters. I have a set in the garage. They have an instant cam-type bearing, which means that some positive tangental force must be applied at all times or the crank will drop the bottom of the stroke. This means it is possible to have the cranks start out of phase, as they can drop independently L or R. I have not used them in a few years at this point, mostly because they require an octalink BB and I don’t have a bike that can take this BB at the moment. And if the optimal number of bikes is N+1, I am at N = 10 which makes for a very crowded garage.

The cranks are super weird and awkward to use at first, and I found myself always concerned with whether the cranks were 180 degrees from each other when they “reset” but after a while, you stop thinking about that and just go. Also, at first I was using psoas to drive the pedal up from 10-1 but after a short period of time, you realize how incredibly inefficient this is, and then you start to use rectus femoris to drive the pedal over the first part of the pedal stroke. This is far more efficient and sustainable, and it happens over time by necessity because the psoas will fatigue very quickly if you try to use it on every stroke.

Now that I think about it, this experience probably helped me formulate some of my theories on “How to Pedal a Bike”…I would like to keep riding these but not enough to buy a whole other bicycle. Although, that is the way to do it. I think these are a really really good off season technique tool. The website has some interesting info on it, although it is pretty dated [my website is nothing flash either so this is kettle = pot].

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Hi Guys,
Thanks for looking in to this for me. Part of my original questions were to ask if any research had been done on these topics and thanks to Ryan’s reply it looks like there has been in spades. At first I thought I may have been asking stupid questions but I’m glad to be proven wrong.



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