150mm cranks

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150mm cranks

Post by johnlvs2run » April 11th, 2021, 7:21 pm

My C2 cranks have now been changed to 150mm. Previous thread here. <--
Thanks to a friendly local machine shop, they drilled the cranks on the flat sections to 150mm.
150mm is an ideal length to drill them, being far enough away from the 170mm holes, and still on the flat part.
I've now been using the 150mm cranks for 3 days, including a workout yesterday, and they are working wonderfully.

Observations so far:
> The 150mm cranks are much, much easier on my knees.
> There are no significant dead spots anymore, including when standing.
> The same drag factors and RPMs can be used as previously without any difference in effort.
> However, to keep the same pedal speed (around the circumference) the drag can be reduced with a higher RPM.
> The calculation to have the same pedal speed at a given pace and lower DF is (for example) 75 RPM x 170/150 = 85 RPM.

Feel free to ask any questions about changing the crank lengths and I will do my best to answer them.

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