Grasschopper

Ok I did a search and it seems this question comes up every few months but I didn't find a great answer. So I am 5'10" tall and just measured my in seam (barefoot, crotch to floor) at 32" (812 mm). Top of femur to floor is 36" (914 mm). My bike came with a 175 mm crank as did my wife's Specialized Sirrus Sport and I think both may be too long (my wife has very similar numbers to mine), but of the methods I have found to calc the proper crank length I get two different numbers: ~168 and ~175. Also looking on Performance at the Ultegra and Dura Ace cranks they seem to come in 172.4 and 175 but not 170 (maybe from other source).

Any thoughts on this? One of my projects this winter will be to update my drive train so when I get a new crank I want to get the right thing but the right thing isn't obvious to me at the moment.

zensuit

I know this is sacreligious, but I have ridden 170 cranks (I am 5-11), 172.5 cranks, and 175 cranks. The 170's were a tiny bit easier to spin...but I didn't notice the huge differences that some folks claim between all three. Why do you feel like the 175 are too long? They are supposed to be of some help in climbing, and where you and I live, that is a serious consideration...so....why too long?

Grasschopper

Well I guess because I am more comfortable spinning and currently I am changing how I ride because I can never seem to spin with these up and sort of slope. I pretty instantly start to mash and my form goes right out the window. Maybe I just need more time too but when I do the change over in the drivetrain I have the perfect oppertunity and want to get the right thing not just what comes standard.

Also anyone got thoughts on crank sets? I would love to get FSA carbon but it isn't in the cards right now. So I was looking at Dura Ace, Ultegra and 105. The Dura Ace seems a little spendy and oddly the hollowtec Ultras are heavier than the 105s (this is all in triples). Should I be looking at other brands?

Corsaire

I just found out that (per the pros' charts on the web, and also per Carmichael/Lance's book) my correct crank size is 170mm.
Now I happen to have both, on my Volpe is 170mm and on my Vigorelli is 172.5mm,
somehow it feels EASIER (a tiny bit) to spin with the 170mm.

Is it worth it to change my Ultegra crank from 172.5 to 170mm ???
Would it be costly ? I wonder ...

Corsaire ;(

zensuit

FSA makes a lightweight, fantastic crankset called the energy that isn't CF...might be worth a look...that's what I am using now and it is very stiff and only 20 Grams more than carbon

Grasschopper

How good are their bottom brackets? I was just going to get the Shimano Ultegra but...

Laggard

No. Spend your money some other way.

LordOpie

I had heard the biggest issue -- even if you're moving to your ideal crank length -- was simply that a person gets used to whatever crank they're on and you can hurt yourself if you don't give yourself a chance to adjust.

And yet, you say you have two bikes with different lengths?

Do you ride both of 'em? If so, do you have any issues going from one length to another?

LordOpie

I know you're an advocate of a longer crank length, so what if the question was reverse? If someone was on 170s and was thinking of going 172.5?

zensuit

I have two different bikes with 170 and 175 cranks....honestly, if I work mostly with the longer crank length and keep my spin as clean as possible, switching down to the shorter crank is only noticeable on climbs, where the bike doesn't "spring" forward quite as much...if I work on my spin on the shorter cranks...then, yes, the difference takes some adjustment.

Z

LordOpie

Why do you have two bikes with different lengths?

Corsaire

The Volpe is my commuter (errands, knock around bike, work commute, etc.) which came with the 170mm.
same with the Vigorelli (club ride, training rides, etc), came with the Ultegra 172.5 mm., didn't have a choice really, and I didn't learn about crank lengths but until later.
To be straight don't feel much of a difference, except for the "easier" spinning on the Volpe (170mm), other than that hasn't affected my biomechanics at all, no pain or anything. I've adjusted both accordingly to seating posture on each bike.

Corsaire

Laggard

I don't think your average weekend warrior/30 mile a day rider could tell the difference between a 170 and 172.5 crank.