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177.5 Cranks for a long femured freak?(6 posts)

177.5 Cranks for a long femured freak?CrazyMan
Jul 15, 2003 5:39 PM
So I went to the LBS for a fitting today. Very good people who know their stuff. I'm 6'2" and as it turns out have EXTREMELY long legs and femurs in particular. The fit revealed two things:
1. I should be on a slack seat tube, ideally ( good thing since the LOOK on its way is 72.5).
2. I should use 177.5 cranks. The rational was that since I was able to spin smoothly up to around 120 rpms with the large cranks, going smaller would be a waste of energy.
Info on crank lenght seems sketchy at best, so any thoughts? Anyone else use such long cranks here?

The great debate--does 2.5 mm matter?Continental
Jul 16, 2003 7:40 AM
I'd go with a more standard 175 mm unless cost are equal. I don't think most riders can tell if the crank length is increased by a tenth of an inch. Is LBS pushing the 177.5 mm crank for some extra dollars?
yes, 2.5 mm matters._rt_
Jul 16, 2003 8:49 AM
don't know about the difference between 175 & 177.5mm since those are lengths i'll never use, but the difference between 170 & 172.5 mm made all the difference in the world for me.

rt - sticking with 170's
So shorter crank arm is better for longer femurs?Kristin
Jul 16, 2003 12:41 PM
I remember you posted your measurments before and you had long legs and pretty long femurs, like I do. I would have thought longer crank arms would be better for longer femurs. Can you explain why the shorter ones work for you better?

Also, I posted a question for you a few days ago about frame sizing. I wasn't sure if you saw it. But basically, I'm wondering if you buy stock frames and if you feel that fit you well, or if you just get used to them over time. Since you have non-typical measurments it seems like you'd have a hard time finding stock frames you'd like. Just curious.
A link and my personal experienceJFR
Jul 16, 2003 11:57 AM

The link will basically support the longer arm length for long leg riders theory.

Personal esperience:

At 6'3'' w/ a 36 inseem, I recently swore I'd need 180s on my first road bike cause that's what I've used on my mtb for the last decade. But despite my gut feeling and the info from the link above, I went with 175s. They were strongly recommended by several trusted roadie friends, including a prior C'Dale team mechanic.

Since May I have almost 800 miles on them now and I'm perfectly happy with them. I ride road 1-2 hrs 3-4 days a week, and mtb 2-8 hrs 1-2 days, so I've been regularly going back and forth between the two bikes.

I typically road ride at a fairly high intensity/HR and a cadence between 93 and 103. My observations of the two arm lengths are:

- When standing on the 175s and thinking about it, I can feel they're a bit shorter and that the leverage isn't quite as good as is on the 180s.

- But seated spinning is what we mostly do on the road, and for "spinning" the 175s seem to "go around" a little smoother than my 180s, especially when sustaining high-ish cadences... my spin naturally feels more circular and power output more even.

Hope this helps. Good luck!

re: 177.5 Cranks for a long femured freak?russw19
Jul 16, 2003 4:24 PM
I built a new bike this winter. When I did, I went from 175 mm Dura-Ace cranks to 177.5 FSA Carbon Teams. When I ordered my cranks, all FSA had in stock in what I needed was 172.5 or 177.5 so either way, I was gonna change. I went bigger and I have never noticed any difference except while cornering. I scraped my pedal on a corner that I didn't think I would have otherwise. Was it the crank, or was I leaning more into the corner because I was pumped about my Campy 10 Pinarello? Can't tell you, but I can tell you that other than that one incident, I haven't noticed a single difference in my cranks to date. BTW, I am 6' and have a 33" inseam. So my legs are shorter than yours. And I am not that flexible. If your LBS fitted you longer, try it. If after the first 3 rides, you feel like it's wrong, ask them to swap to 175's. Are you getting the bike from them? If so, and it was at my shop.. I would swap them for you.