AnthonyG

The drawing is 707mm from the centre of the Bottom Bracket (BB) to the top of the saddle. Then add 172.5mm and your at around 880mm.

When we talk about your cycling inseam its from the pubic bone to the floor in bare feet, not pants inseam.

If your actual inseam is say really 31" or even 32" then I would still recommend some 165mm cranks.

Anthony

Cyclist0108

Hmm.

I know the 707 mm length is definitely right, as I have measured it myself, and transferred it to another bike, and have found that I deviate from 707 mm, it is uncomfortable. (In fact, I started off thinking it was slightly too low, but got hip pain when I raised it 5 mm). I don't rock in the saddle. But 880 mm is up to my belt buckle, so something doesn't add up. Maybe it is the foot length? The top tube mashes in my nuts with a standover height of 775 mm. (=30.5 in)

AnthonyG

Maybe the difference is in your feet.

Another way to assess crank length is to consider how comfortable you are riding in the drops. Can you ride in the drops with your elbows bent with a flat back for a decent period of time in comfort? Do your knees/thighs rise into your chest when your back is flat?

Anthony

IK_biker

Bwa ha ha ha ha....

How does this matter?
Are you fitting your bike to the pants, or to the rider?

Cyclist0108

Is your bicyclist measurement of "inseam" 4.5" longer than your pants inseam?

Here is a picture showing bicyclist "inseam" being measured:



If I do it this way, I can get 30.5" (as mentioned previously, as this is consistent with the 775 mm standover height on my bike.) Since the 707mm length combined with the 172.5 mm >> 775 mm, something else must be going on (as the fit is as close to ideal as I have experienced).

Cyclist0108

I ride a lot more upright now nearing age 54 as I did when I was 24, but I don't think it is because of the cranks (more just being too fat and inflexible). I will check next time I am on the bike, but I don't think I have a clearance issue, with the tops of the bars level with the seat.

McBTC

Maybe think about approaching it a bite at a time beginning with whatever seems most important--e.g.,

... try out a taller freewheel or go to the smaller chain ring and conquer those "ultra-steep hills" you talked about by going to the sub 1:1 gearing that you mentioned.

... experiment with shorter cranks to address flexibility issues (e.g., Ride2 crank shorteners).

The latter makes sense because even if you invest in 165 cranks as part of getting smaller chain rings, you may still be interested to use crank shorteners to go below 165.

McBTC

Also, you may be able to drill the Campy Athena for shorter cranks. Interestingly, this site comes to different conclusions about ideal crank length...

Bicycle cranks: Check your Cranks!

--> 162.5 mm...?

MichaelW

Fit advisers who are not obsessive about getting the right length of crank for the rider's leg length are most likely medium sized fit advisers.
For us med riders, we have a multitude of medium sized cranks with which we can fine tune the crank length for our physiology and flexibility.
Short and tall riders don't have that luxury. Every common crank length is too big for a short rider and too short for a tall rider.
The first iteration of crank sizing should be for leg length.
Once you know what a normal crank is for a rider of this size, you can proceede to the next iteration, which is flexibility. Once you have adjusted for rider flex, you can look at the other physiological factors.
For most riders, the first two iterations are more than sufficient.

KramesJamer

This addresses my original post... I think fit is super important, and more so, the longer the event is. Given the kilo on the track is from a standing start, in a fixed gear that needs to be as big as you can maximally ride at speed for ~1:10, it really puts an importance on getting off the line. When I rode shorter cranks, I was more aero with the saddle higher and my hip angles more open, but my starts were HORRIBLE. I'm thinking if you can maximize the lever for the start, and the first ~20seconds are standing before you transition into seated aero position, you really could tolerate the more closed hip angle for 50 seconds, but get on top of the gear much faster... no???

I appreciate the thoughts.

vincentvergara

I'm going to try to use this account instead of my old one, ESTrainSmart. This is a great example showing how you can exploit someone's weakness if you know what crank they're using.

With a short crank, starts will be a lot slower, but your potential max sustained speed will be a lot higher (higher max cadence). Attacks will be less explosive, more long lasting.

With a long crank, starts will be a lot faster, but your potential max sustained speed will be a lot lower (lower max cadence). Attacks will be more explosive, but short lived.

You don't want it so short that even if you reach the highest top speed, you've sacrificed too much distance in the beginning for it to matter. Too long and you'll have a great jump at the beginning, but then lose it all towards the end. Flexibility and mobility matter A LOT more with longer cranks, and an easy telltale sign that it's lacking is if you can't hold a neutral spine or your hip feels restricted at the top of the pedal stroke. Mostly everyone I coach have inflexible hamstrings and hip flexors, and poor mobility at the ankle combined with some sort of arch deficiency masked by shims. I have a love/ hate relationship with shims because it reinforces weaknesses in the ankle, but that's a different discussion.