Crank Length Q

[false_aesthetic]

Bear with me on this one . . .
I've noticed a tiny, tiny pause at the top of my pedal stroke. I've been looked at a few times to adjust saddle height + fore/aft position. Raising my saddle helps reduce that pause but starts to irritate my hamstrings after an hour or so (I'm pretty This got me to wondering if a shorter crank would be helpful.

Well, I finished up my track bike and popped some 167.5mm cranks on it. Same saddle height, setback and saddle-to-bar drop. Things feel smoother at the top of the stroke and all around better (especially at a higher output) but I'm left wondering if it feels better because I'm on a fixed gear and I'm being "forced" through the top of the pedal stroke.

The obvious test would be to grab some 167.5 road cranks and throw them on my bike but they're hard to come by -- and I really don't want to throw down the $$$$$$ for DuraAce (or Sugino) cranks just to try it out.

There's a bunch of cheaper cranks available in 165mm lengths. The question is whether its worth it to drop the cash on one of those options to test it out or if I'm thinking about this all wrong.

Thanks

[David Tollefson]

Could you swap the track cranks (with a road chainring) onto the road bike just as a test?

[Chik]

What length do you have on the road bike now?

If you google crank length, there are many bike fit pundits talking about the benefits of shorter cranks. Some of them have nifty formulae to calculate what ought to be your ideal length.

Anyway, I always had 170 road cranks (mainly because Campag's shortest until recently was 170) but, like you, felt that 165 track cranks were much better for me. A few of the calculation formulae proposed on the web put my ideal length at much less than 160 although I didn't bother remembering the actual numbers since they were not readily available. Long story short, I got 165 for my new road bike and can't be happier.

Biomechanic theory apparently puts efficiency over power (leverage). I understand that shorter cranks give you better efficiency, and the benefits overweigh those of higher leverage / power per pedal stroke of longer cranks since one tends to deal with a few pedal strokes during a ride. Also, higher efficiency apparently makes you a better climber.

When I used to race BMX, I had 172.5 and thought, at the time, was the right length compared to 170. I think I would not go any longer than 165 now, regardless of the type of bike.

[guido]

I'm 6'1" and have a 34" inseam. I use a 165 crank length on all my bikes. Knees have never been this happy. Go for it.

[false_aesthetic]

@Chik I'm currently running 170mm Ultegra cranks (mid-compact). The formulas I've looked at put me right around 170mm.
@david I'll try swapping the cranks but there's a big Q-factor difference between Ultegra and Miche (IIRC 146 vs 131) they might not fit but its worth a try huh?

[Chik]

The formula based on height yields 170 for me, but suggestions referenced here put me at about 159.
CRANK LENGTH - Which one? - The Steve Hogg Bike Fitting Website
Disclosure: I was fitted by a Hogg trained fitter on an older bike with 170 Campag cranks, but he did not say anything about crank length probably for practical reasons mentioned previously.

[false_aesthetic]

Thanks Chik!

[11.4]

There's no formula that will determine your ideal crank length, and you're a perfect example of why. There's a theory (mostly just theory) of how a particular crank arm length gives you the most power translation, but more importantly is how well your joints (knee and hip in particular) accommodate a circle of rotation for a larger crank arm. If you have some limitation (whether bone impingement or muscle or tendon inflexibility or something else), you won't be able to power through the top or bottom of your stroke correctly and you'll have that coasting moment you describe. Second, if your thigh is hitting your pelvis or your stomach/chest at its high point, it may just coast through because it's being blocked from free rotation at that point.

Yes, your fixed drive will push your foot through the top and bottom extremes of the pedal stroke, but you don't have to leave it that way. It's always likely to be much weaker than the mid-point power points in the crank rotation (and you may be feeling weakness, not inability to push at all). I'd look at your position to make sure you aren't so low that you are impinging on your legs' ability to power through the rotation. You don't have to go nuts about crank arm experiments -- you may well be having the same problem at shorter crank arm lengths as well, your sensation of smoothness notwithstanding (it's very hard to feel whether you are genuinely applying power at the top or bottom of the stroke).

[HarryBeast]

Something that I have been asking myself: The dichotomy of spinner vs masher (is that the right term?) - does it have any relation to the muscular setup of an individual? What I mean is a predominance of fast-twitch or slow-twitch muscle fibers.

[false_aesthetic]

I'm about 5 hours into 165mm cranks.
Took about 10 min to get used to them the first day.
Feels really good so far.

But this is all on the trainer. We'll see how I feel on the road.