Crank length myth

dkrenik

Doh! I sit corrected
Dave

frenchyge

Nothing wrong about what you've said here, but since pedal force is the prime mover I'd phrase it that shortening the cranks means you are getting less torque for the same pedal force as you were applying before. You'd have to increase cadence (or gearing) proportionally to overcome the reduction in torque if you wanted the same power output as before.

Edit: IOW, you guys are saying the same thing but looking at it from different ends of the bike -- Dave wants to increase cadence and Swampy wants to increase pedal force.

rmur17

yeah but what if you were driving a human-powered light airplane .. or <g> a nuclear sub in the Gulf stream?

__________________
rmur

frenchyge

I've ridden a stationary bike *on* a nuclear sub in the Gulf Stream. Talk about confusing....

swampy1970

No I don't, that's why I ride 180mm PowerCranks. I used to ride 185mm TA Alize cranks but that's when I didn't have a BBQ and beer induced gut. You should try 220mm cranks whilst seated on a 25% hill. Where's the *love* emoticon when you need it - but just don't ask me to pedal at more than 70rpm on those! I can see yoga classes in my future though!

A 13 rpm difference sounds like a 2 or more sprocket increase... A drastic change but each to his own I guess.

Steve_B

Which direction did the toilet flush swirl when you did this?

frenchyge

They don't always flush well against sea pressure, so I was just thankful when it went down instead of coming up!

Steve_B

Right.

To answer someone else's question, I would agree that the longer cranks were limitiing me. When your knees are hitting your chest with mild force while you are on the rivet, it's a limiter.

The other thing going on was that I was at that time still using a 55 big ring in the front. There are bigger differences in gear-inches/development between adjacent gears using a 55 than there are using a 53 or a 50, and this affects your comfortable cadence and which gear you pick at a given speed. IMO, it was often difficult to find a comfortable gear in any given situation. I don't have a really good techie explanation for this but the end result was that I was sort of stuck in a mashing gear at around 80 rpm often because that was what felt comfortable with the 175 cranks.

I made the transition to 170 cranks and this forced me to spin more and it was sort of liberating once I got the hang of it. Then I decided that using a 55 big ring was stupid for me, changed to a 53 and all has well with the world ever since.

tonyzackery

Discussion on this topic must also consider the size of the individual's foot because a longer foot will lengthen the lever, and too much of a good thing can be a bad thing...

Anyway, in my case (relatively short femurs and long feet) I've found I'm much more efficient (lower heartrate for given wattage and cadence) and have increased sustainable power on 170mm cranks versus my old 175s. Inseam 34" and size 48 feet...

531Aussie

Ha! This is interesting, because I felt like I was going about the same speeds for slightly lower heart rates when I went from 180s back to 170s and 172.5. With the shorter cranks, it was a weird feeling; it felt like more of a short stomp, and that I was using less quad for the same output and speed. Short cranks feel like you're up high and stomping aluminium cans, and very long cranks feel like you're doing leg-press with your knees in your chest

Yes, I reckon foot size should be included

531Aussie

so, I rode my 'long crank' bike the other night, with the 177.5s.

The ride was a group thing with hard efforts over short hills (300m to ~1.5km). As I said above, the long cranks are great when you're off the saddle and 'levering' over the hills at low/moderate revs, but as soon as you sit down to pedal, that's where the position compromise comes in.

Funny; after about an hour on the 177.5s, I get sick of trying to push them ,with my knees coming up so high, and I find myself getting off the seat to 'get over' the pedals.

In my opinion (cadence aside), long cranks are a compromise between extra leverage and being in a lower/weaker position, so you've gotta work out if the extra leverage outweighs being in a worse position, or vice versa.


By the way, this is a 'nifty' little article about a couple of the conundrums of long cranks:

http://www.arniebakercycling.com/pu...rm%20Length.pdf