Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

crank

Old 03-02-05, 11:14 PM
  #1  
halimec05
officially vulgar
Thread Starter
 
Join Date: Feb 2005
Posts: 23
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
!!!!!

Last edited by halimec05; 11-05-05 at 02:26 AM.
halimec05 is offline  
Old 03-02-05, 11:18 PM
  #2  
forum*rider
Work hard, Play hard
 
forum*rider's Avatar
 
Join Date: Dec 2003
Location: San Diego, California
Posts: 2,596

Bikes: Cannondale super V 500, Bianchi Piaggio(hopefully getting a new road bike when I get some money)

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
172.5mm seems kind of short for someone as tall as you. I'm about 5' 5" and I use 172.5mm cranks.

Maybe you could just run a lower gear and spin more with the 175mm cranks? The longer the cranks the more leverage so if you kept the 175mm cranks and spun a smaller gear then it would be easier than using a 172.5mm crank and spinning the same gear.

I have no idea if that made any sense at all, sorry if it didn't.
forum*rider is offline  
Old 03-02-05, 11:18 PM
  #3  
53-11_alltheway
"Great One"
 
53-11_alltheway's Avatar
 
Join Date: Feb 2005
Location: Might as well be underwater because I make less drag than a torpedoE (no aero bars here though)
Posts: 4,463
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Why not?

Just make sure you have low enough gearing to compensate. That's what's going to really take pressure off your knees.


I'm 6'2" and I run 180mm, but I've had 170mm and 175mm before.


Originally Posted by forum*rider
Maybe you could just run a lower gear and spin more with the 175mm cranks? The longer the cranks the more leverage so if you kept the 175mm cranks and spun a smaller gear then it would be easier than using a 172.5mm crank and spinning the same gear.
I agree. His knee problems might be a side effect from not having low enough gears, not neccessarily too long of cranks.

Last edited by 53-11_alltheway; 03-02-05 at 11:23 PM.
53-11_alltheway is offline  
Old 03-02-05, 11:32 PM
  #4  
CAAD5AL
Senior Member
 
CAAD5AL's Avatar
 
Join Date: Jan 2005
Location: SLC, UT
Posts: 692
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I'd like to hear some other thoughts on this one too - I've never really understood how the 2.5MM differentials are really meaningful in a practical sense . . . you know what I mean?
CAAD5AL is offline  
Old 03-03-05, 12:45 AM
  #5  
53-11_alltheway
"Great One"
 
53-11_alltheway's Avatar
 
Join Date: Feb 2005
Location: Might as well be underwater because I make less drag than a torpedoE (no aero bars here though)
Posts: 4,463
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by CAAD5AL
I'd like to hear some other thoughts on this one too - I've never really understood how the 2.5MM differentials are really meaningful in a practical sense . . . you know what I mean?
2.5mm is not that much.

However, it will feel like a 5mm difference in saddle height to your knees.
53-11_alltheway is offline  
Old 03-03-05, 02:39 AM
  #6  
CAAD5AL
Senior Member
 
CAAD5AL's Avatar
 
Join Date: Jan 2005
Location: SLC, UT
Posts: 692
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by 53-11_alltheway
2.5mm is not that much.

However, it will feel like a 5mm difference in saddle height to your knees.
Well, not to be a pest, but not really if you think about it. Saddle height adjustments change the total extension of the leg in absolute amounts - 5mm higher and your leg is 5mm more extended at the bottom and top. A longer crank just makes it a little longer at the bottom, which you adjust out by lowering the saddle, and a tiny bit more flex at the top.
CAAD5AL is offline  
Old 03-03-05, 02:55 AM
  #7  
53-11_alltheway
"Great One"
 
53-11_alltheway's Avatar
 
Join Date: Feb 2005
Location: Might as well be underwater because I make less drag than a torpedoE (no aero bars here though)
Posts: 4,463
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by CAAD5AL
Well, not to be a pest, but not really if you think about it. Saddle height adjustments change the total extension of the leg in absolute amounts - 5mm higher and your leg is 5mm more extended at the bottom and top. A longer crank just makes it a little longer at the bottom, which you adjust out by lowering the saddle, and a tiny bit more flex at the top.
Yeah, If you go with a 2.5mm longer crank you should lower your saddle 2.5mm to compensate. Since your saddle is lowered 2.5mm and the crank is 2.5mm longer at the top also, your knees see 5mm.
53-11_alltheway is offline  
Old 03-03-05, 04:52 AM
  #8  
MichaelW
Senior Member
 
Join Date: Feb 2001
Location: England
Posts: 12,952
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 17 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Your current cranks are about right for your size. I don't think you would benefit much from switching to smaller cranks.
You may want to change your pedalling style, use a smaller gear and spin faster.
Although 175 are often thought of as long cranks, for your size they are normal.
MichaelW is offline  
Old 03-03-05, 07:30 AM
  #9  
531Aussie
Aluminium Crusader :-)
 
Join Date: Apr 2004
Location: Melbourne, Australia
Posts: 10,040
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 13 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
If I were you I'd keep the 175s. Many people would even suggest you should be using 180s, depending, of course, on your inseam length. A 2.5mm (1.4%) decrease in length would do very little.

Cranking lower gears at higher revs should reduce pressure on your knees, but the better thing to do would be to maintain a regular stretching routine......like we all should be doing

The issue of knee flexion and crank length is a confusing one. I've been looking into it recently because I've just gone back to 175s after using 170s for a couple of years.

It seems to me that longer cranks will increase knee flexion between about 8 o'clock and 2 o'clock of the pedal stroke, but I figure there's less flexion between 2 o'clock and 8 o'clock (I could be wrong). I suspect that I do most of my pushing between about 1:30 and 6:30, therefore, in my situation, would long cranks reduce knee pressure do to less flexion through that section of the pedal stroke?...........dunno
531Aussie is offline  
Old 03-03-05, 07:37 AM
  #10  
Ezekiel 25.17
Junior Member
 
Join Date: Mar 2005
Posts: 5
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Hi,

I would actually consider 172.5. Personally, I can feel the difference, especially when tired, after weights... Reduce load, spin faster and save your knees! (nice slogan, huh?)
Ezekiel 25.17 is offline  
Old 03-03-05, 07:57 AM
  #11  
galen_52657
Banned.
 
galen_52657's Avatar
 
Join Date: Jun 2004
Location: Towson, MD
Posts: 4,020

Bikes: 2001 Look KG 241, 1989 Specialized Stump Jumper Comp, 1986 Gatane Performanc

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
My knees will be 48 in May. At 6'4" tall, I have been riding 180 mm cranks for 18 years or so. I am considiering longer cranks. Knee pain is not directly related to crank length. One can slog along at 50 rpm riding short cranks as well as long cranks. One can ride too much on the first warm day using short or long cranks. My knees feel just fine thanks, but then I never suffered any knee injuries...did not play college football...played a lot of tennis and ran...but that hurt my back, not my knees.

It is also a misconception that one cannot 'spin' on long cranks. When I am in a pacelline, I am in the same or a lower gear than most of the riders in the group.

A lot of knee discomfort and pain is because of the saddle being set to high or to low, cleats/shoes miss adjusted or plain old overuse. If you have not riden more than an hour in the last month, don't go out and do 3 hours next time back on the bike.
galen_52657 is offline  
Old 03-03-05, 09:23 AM
  #12  
Brillig
Bananaed
 
Brillig's Avatar
 
Join Date: Feb 2003
Location: Philly-ish
Posts: 6,426

Bikes: 2001 Lemond Nevada City (only the frame remains)

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I would highly recommend against smaller cranks.

Despite common mythology, you shouldn't be considering "leverage" or force when you consider crank length (Technically they do effect each other but only in a given gear, and that's what having multiple gears is for, so you're not tied to that). If you shift correctly there should be no correlation between longer crank lengths and mashing.

What you really should be concerned about is your range of motion in the pedal stroke. And too small a range of motion for your leg size will be harder on your knees, not easier.

I don't know your body proportions but at 6'2" I'm very confident in saying 175 is an absolute minimum, and you should be thinking about 180 (or longer if you can find them).

Lennard Zinn has become a bit of an expert on cycling fit for above average height people. Check out his investigations into crank length (starts out as a sales pitch for his custom cranks but gets more into the reasoning behind it as you go): http://www.zinncycles.com/cranks.aspx
__________________
If once a man indulges himself in murder, very soon he comes to think little of robbing; and from robbing he comes next to drinking and Sabbath-breaking, and from that to incivility and procrastination.
- Thomas De Quincey
Brillig is offline  
Old 03-03-05, 10:04 AM
  #13  
CAAD5AL
Senior Member
 
CAAD5AL's Avatar
 
Join Date: Jan 2005
Location: SLC, UT
Posts: 692
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by 53-11_alltheway
If you go with a 2.5mm longer crank you should lower your saddle 2.5mm to compensate. Since your saddle is lowered 2.5mm and the crank is 2.5mm longer at the top also, your knees see 5mm.
Yeah, I follow the logic and everything, I've just never believed that that slight incremental angle in the knee at the top of the stroke has any real bearing on knee wear and tear, at all. Knees are made to bend! And any increased burden from the added crank length is offset by gearing . . . anyway, just my opinion, but I wouldn't invest in a 2.5mm crank length change and anticipate any appreciable changes in the bike or comfort.
CAAD5AL is offline  
Old 03-03-05, 10:08 AM
  #14  
Brillig
Bananaed
 
Brillig's Avatar
 
Join Date: Feb 2003
Location: Philly-ish
Posts: 6,426

Bikes: 2001 Lemond Nevada City (only the frame remains)

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by CAAD5AL
Yeah, I follow the logic and everything, I've just never believed that that slight incremental angle in the knee at the top of the stroke has any real bearing on knee wear and tear, at all. Knees are made to bend! And any increased burden from the added crank length is offset by gearing . . . anyway, just my opinion, but I wouldn't invest in a 2.5mm crank length change and anticipate any appreciable changes in the bike or comfort.
1. It's the opposite, increasing crank length decreases the energy you need to apply in a given gear.
2. You're absolutely right, the range of crank lengths of a whopping .5 cm is ridiculous and outdated. Hopefully we'll start to see 120 through 220 mm cranks to better fit the range of actual people that ride bikes.
__________________
If once a man indulges himself in murder, very soon he comes to think little of robbing; and from robbing he comes next to drinking and Sabbath-breaking, and from that to incivility and procrastination.
- Thomas De Quincey
Brillig is offline  
Old 03-03-05, 01:38 PM
  #15  
Phatman
Senior Member
 
Join Date: Sep 2002
Location: NC
Posts: 3,411
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Brillig
1. It's the opposite, increasing crank length decreases the energy you need to apply in a given gear.
2. You're absolutely right, the range of crank lengths of a whopping .5 cm is ridiculous and outdated. Hopefully we'll start to see 120 through 220 mm cranks to better fit the range of actual people that ride bikes.
well, shorter cranks put less stress becuase they move your legs through a smaller range of motion. a shorter path is taken per pedal stroke. it effectivly increases the gear ratio, however, it helps those with inflexible knees becuase it puts them through a smaller range of motion. I have 170s on my fixed gear and I'm 6'1''. I DEFINITLY notice the difference from my 175s on my road bike. I find the 170s more comfy at high cadences than the 175s.
Phatman is offline  
Old 03-03-05, 06:37 PM
  #16  
531Aussie
Aluminium Crusader :-)
 
Join Date: Apr 2004
Location: Melbourne, Australia
Posts: 10,040
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 13 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Brillig
Hopefully we'll start to see 120 through 220 mm cranks to better fit the range of actual people that ride bikes.
so, just after the bike companies have cut costs by standardizing frame and fork sizes as best they can, you want them to provide different bottom bracket heights?

Good luck....they won't like it
531Aussie is offline  
Old 03-03-05, 09:20 PM
  #17  
Brillig
Bananaed
 
Brillig's Avatar
 
Join Date: Feb 2003
Location: Philly-ish
Posts: 6,426

Bikes: 2001 Lemond Nevada City (only the frame remains)

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by 531Aussie
so, just after the bike companies have cut costs by standardizing frame and fork sizes as best they can, you want them to provide different bottom bracket heights?

Good luck....they won't like it
BB height should correlate to frame size. No?
__________________
If once a man indulges himself in murder, very soon he comes to think little of robbing; and from robbing he comes next to drinking and Sabbath-breaking, and from that to incivility and procrastination.
- Thomas De Quincey
Brillig is offline  
Old 03-03-05, 09:31 PM
  #18  
srf
Senior Member
 
Join Date: Mar 2003
Location: Bothell, WA
Posts: 125
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I would recommend getting a bike fit before getting shorter cranks, as 172.5 is by most accounts too short for you; having a good fit is an especially good idea since you're having knee problems. Don't know what pedals you use, but float or the lack thereof could also be an issue.
srf is offline  
Old 03-04-05, 12:32 AM
  #19  
Fox Farm
Senior Member
 
Fox Farm's Avatar
 
Join Date: Aug 2004
Location: Prague, Czech Republic
Posts: 2,535

Bikes: Merlin Extra Light, Orbea Orca, Ritchey Outback,Tomac Revolver Mountain Bike, Cannondale Crit 3.0 now used for time trials.

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 54 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I think that all the responses to this post have been pretty on target.

I am the same height and age as Halimec and ride 175s, always have, and they work for me. I have borrowed a bike with 172.5s and noticed the difference and did not like how they flet. If you are having knee pain, and are using what is the suggested correct size crank arm lenght, then perhaps you need to have a professional fitting or set up done. Yea, you've been riding for 20 years, but perhaps many of those years have been riden with improperly aligned cleats, seat for and aft, maybe it's you riding style (no criticisims here, just asking questions).
Fox Farm is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.