A crankarm length question...

Discuss light weight issues concerning road bikes & parts.
User avatar
yourdaguy
Posts: 2206
Joined: Thu Mar 17, 2005 3:25 am
Location: Southern Indiana USA
Contact:

by yourdaguy

Yea, I have 175 on everything; road, MTB, and tandem. My legs are used to spinning those circles.
For certain parts stiffer is more important than lighter.

veloflyte
in the industry
Posts: 88
Joined: Sun Sep 27, 2009 3:08 am

by veloflyte

User Name wrote:
Frans wrote:Basso tried to have an adjustable seatpost in the 2011 Giro. (a much simpler mechanism than this proposal) That caught on like a chocolate teapot.

Ha ha! I want one of those posts! :D To be fair to the company, I think it was something that Basso just wanted for himself, rather than a product that they really thought was gunna sell tons of.

I would pay hundreds of bucks for one. In search of one, I started a thread about them (here, I think), and even emailed FSA, but had no responses.

I'm one of those dudes who always adjusts his seat height, mostly because my lower back is a bit dodgy, and the difference between what feels comfortable on a good and bad day can vary up to 7mm! I also like to be a little lower for strong head and crosswinds.

Sorry to hijack the thread there for a moment.

The "changing crank length" is something I might be interested in, provided, of course, that it was 100% reliable, and without creaks, clicks or any perceived movement in the arm. I imagine extra weight and cost could be an issue. I like having longer cranks for off-the-saddle stomping, so I reckon it would great to flick a switch and have 185mm to sprint over to a breakaway. Seat height would also be an issue, because almost all people adjust the seat height for a different crank length


I, too, used to have trouble with my seat height. I was always moving my saddle up, moving it down a few days later, then moving it back again. My answer was that I did not have my seat high enough. AFter Ric Hjertberg did a fitting for me at the old Wheelsmith in Palo Alto, I realized that i should be running a much higher saddle. It took me more than a year to adjust, slowly bringing my seat up. But now, with my higher saddle, I am very, very happy.

by Weenie


veloflyte
in the industry
Posts: 88
Joined: Sun Sep 27, 2009 3:08 am

by veloflyte

yourdaguy wrote:The problem with this idea is that most people take a period of time to adjust to a different crank length. Some even initially have knee problems because of the different angles of the knee with different lengths. Also, when you change crank length you must change the seat height, all things else being equal. So I see no market for cranks that can change on the run so to speak. The Look cranks are a great idea for someone that is not sure of their size, for dealers that don't want to stock 3 sizes of cranks, for people that share a bike, for a father that wants to give a bike to a child later, etc. but changing on the fly provides no benefit that I can see.



Ahhh...here's some interesting thoughts related to that... Many years ago, I used to work at the Wheelsmith Inc. in Palo Alto, CA. While there, Miguel Indurains Tour de France winning time trial bike was put on display for a month at the store. Now I'm a taller rider, so I was happy to see that Big Mig did, indeed, use 180mm cranks on his TT bike. But a very interesting bit of information came to me through Ric Hjertberg (wheelsmith founder and now MadFiber wheel designer/founder) about Miguels fit... His personal mechanic said that even though Migule used both 175mm and 180mm cranks on his bikes, he NEVER changed his saddle position. At first, I thought this was ridiculous. But then, after some consideration, it started to make sense to me. So, I took my own bike and set it up just that way....so that two crank lengths could be used without altering the saddle position. I've been riding this way ever since and it is perfect. It is my opinion that we, as riders, do Not become familiar to a certain saddle position related to the lowest point on the pedaling circle, but rather that we become familiarized to a saddle height in relation to the bottom bracket center.
Here's how it works... You set your saddle as high as possible on the longest crank you are going to use, then whenever you put shorter cranks on, you will never be overextending...which is, or course, a most dangerous position to be in.
It actually aids the whole situation in that, when you have shorter cranks on, you naturally pedal faster, which necessitates a lower saddle in order to pedal smoothly.

I'm not saying it will work for everybody. But after trying it myself, I can't imagine doing it any other way.

User avatar
yourdaguy
Posts: 2206
Joined: Thu Mar 17, 2005 3:25 am
Location: Southern Indiana USA
Contact:

by yourdaguy

Velloflyte: that is very interesting and I can see how it would work. I think that most people would set up their 175 cranks to the point where they had max extension and then when moving to 180's would move the seat. So if you want to have variable cranks, you would have to set seat to longest crank position and then use other lengths from that position.
For certain parts stiffer is more important than lighter.

User Name
Posts: 596
Joined: Tue Jun 07, 2005 3:32 pm

by User Name

veloflyte wrote:
I, too, used to have trouble with my seat height. I was always moving my saddle up, moving it down a few days later, then moving it back again. My answer was that I did not have my seat high enough. AFter Ric Hjertberg did a fitting for me at the old Wheelsmith in Palo Alto, I realized that i should be running a much higher saddle. It took me more than a year to adjust, slowly bringing my seat up. But now, with my higher saddle, I am very, very happy.

Thanks. Good tip, but I might be the opposite: my problem may be that I try to have my saddle too high. Ya see, about once a week, I kid myself that I can have my seat the same height as it was when I was 25, when I was more flexible. :D

User avatar
elviento
Posts: 1235
Joined: Thu Aug 25, 2005 7:09 pm
Location: In the industry
Contact:

by elviento

Firstly, always good to see someone trying to come up with noval designs. That makes the world more fun.

That being said, would one need size-adjustable shoes by touching a belt mounted button? Would be nice to have it on a fitting machine though.
Fast falcons: http://www.youtube.com/watch?v=j3mTPEuFcWk" onclick="window.open(this.href);return false;
www.falcobike.com
Facebook: falcobikeglobal

Pantani
Posts: 863
Joined: Tue Jan 11, 2005 11:40 pm
Location: Eire

by Pantani

I find it very difficult to see how one could have an on the fly adjustable crank length and not suffer a penalty in weight or mechanical integrity. But even if that were not the case it looks like a solution in search of a problem - especially since the Look trilobe system and several others allow length changes using simple tools.
Not everything that counts can be counted. Not everything that can be counted counts.

Post Reply
  • Similar Topics
    Replies
    Views
    Last post