Crank Length

[Bopomofo]

No, no, no... it is still 0.5% difference. What happens if you miss your PB by 0.5%, hmm?

Even though it is pointless, it is probably best to buy three different crank sizes, just in case.

[birdyman]

When i was having my fitting at B'Town last month, Mike and Josh came and had a good long look at me pedalling away and then asked me if I thought that they should reduce the crank length by 2.5mm. I was a bit lost for words as it sounded like a negligible change, but they assured me that it would make a difference to comfort and power delivery. So they did.

I had no frame of reference by which to make a comparison, but if Mike reckons that it is worth it, then I don't suppose that any of us would argue with his Yoda-esque wisdom.

[King Sad]

From what research I have been able to do crank length is actually quite important, get it wrong and you end up with knee pain; my optimal length is 159mm as I am a short arse but have a 165 as that is the shortest I can find.

Short crank; less force, higher cadence, less time in dead spot, shorter stroke through strongest leg movement. Long cranks reckoned to be better on climbs as they allow more leverage.

http://www.machinehead-software.co.uk/b ... lator.html

[tesseract]

I'm pulling together a spreadsheet that will give you seat height and crank length, or at least let you play around with the different options.

I need to find some more technical stuff about power output, crank length, and leg angles.

I'm happy with what I have for the seat height, however it seems to me that the common calculations for seat height create too acute an angle at the top of the pedal cycle which is where the power loss is, but this might be unavoidable.

What I'm seeing so far is that small changes in seat height, and crank length make little difference to the angles involved, which would tie in with there being minimal impact to power output. The downside of any studies on this is it's hard to account for muscle adaption, ie your legs learn to put the most power out in the angles they're used to, so changing position might not give an immediate improvement.

EDIT: Been reading a lot of interesting stuff on crank length, there's a LOT of contrasting views The most scientific stuff boils down to this:
> A shorter crank has minimal impact on power, although there is some evidence a longer crank helps on hills.
> A shorter crank allows a higher cadence, so with approx the same power you get more revs
> A shorter crank allows a higher saddle (saddle height remains the same, but the bottom of the pedal stroke is higher, so the seat can be as well. Potentially more aero?
> A shorter crank means a bigger angle at both hip and knee at the top of the stroke, which helps prevent injury, and helps maintain power (possibly offsets the shorter crank length/ leverage?)

The downside is I don't have a power meter, or garmin, or budget to experiment, but I def think I'll be trying a shorter crank.