Go Back  Bike Forums > Bike Forums > General Cycling Discussion
Reload this Page >

How often should you change pedal cranks?

Notices
General Cycling Discussion Have a cycling related question or comment that doesn't fit in one of the other specialty forums? Drop on in and post in here! When possible, please select the forum above that most fits your post!

How often should you change pedal cranks?

Old 06-07-14, 05:14 AM
  #1  
oggyeater
Newbie
Thread Starter
 
Join Date: May 2014
Posts: 2
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
How often should you change pedal cranks?

On a recent ride went to put the power down on a hill and right hand pedal ( shimano 105) crank snapped in the middle, landed thigh on broken end, anyway I have been told pedal cranks should be replaced every 3 years ish?! Didnt realised it was that common as have to replace whole crankset and bottom bracket, do they snap that often?
Attached Images
File Type: jpg
IMAG0206.jpg (104.5 KB, 56 views)
oggyeater is offline  
Old 06-07-14, 05:41 AM
  #2  
xenologer
Senior Member
 
Join Date: Aug 2008
Posts: 2,589
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 237 Post(s)
Likes: 0
Liked 1 Time in 1 Post
normal end of life failure for crankset is at the pedal eye, where spider meets arm, or taper interface.
and typically happens years after you've already sold the bike on craigslist to someone else.
break mid arm like yours is not standard

were there warning signs such as creaking noises in the weeks before ?
did a badly adjusted front derailer scour a mark on the crank arm that led to cracking ?
crash in the past ?
xenologer is offline  
Old 06-07-14, 06:08 AM
  #3  
oggyeater
Newbie
Thread Starter
 
Join Date: May 2014
Posts: 2
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
No creaking, no misalignment, maybe fault or weakness on outside?, no real crashes on bike, just dont think it should have snapped, wear and tear? Do yo know of many? Are photos showing?
Attached Images
File Type: jpg
IMAG0206.jpg (104.5 KB, 58 views)
File Type: jpg
IMAG0207.jpg (101.2 KB, 89 views)
oggyeater is offline  
Old 06-07-14, 06:42 AM
  #4  
wahoonc
Membership Not Required
 
wahoonc's Avatar
 
Join Date: Jan 2005
Location: On the road-USA
Posts: 16,855

Bikes: Giant Excursion, Raleigh Sports, Raleigh R.S.W. Compact, Motobecane? and about 20 more! OMG

Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 67 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Got a picture directly down on the break? I have cranksets that are over 50 years old that are still going strong. I have only had one crank set break at the pedal eye... happened to my brother when he borrowed my bike.

From your second picture is looks almost like there was an existing crack...

Aaron
__________________
Webshots is bailing out, if you find any of my posts with corrupt picture files and want to see them corrected please let me know. :(

ISO: A late 1980's Giant Iguana MTB frameset (or complete bike) 23" Red with yellow graphics.

"Cycling should be a way of life, not a hobby.
RIDE, YOU FOOL, RIDE!"
_Nicodemus

"Steel: nearly a thousand years of metallurgical development
Aluminum: barely a hundred
Which one would you rather have under your butt at 30mph?"
_krazygluon
wahoonc is offline  
Old 06-07-14, 08:30 AM
  #5  
slorollin
Senior Member
 
slorollin's Avatar
 
Join Date: Mar 2010
Location: Eastern NC
Posts: 304

Bikes: '81 Puch '13 Cafe Noir

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 22 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
"From your second picture is looks almost like there was an existing crack..."

I agree. See the oxidation that has set in on part of the break? That crack has been there a while indicative of some past trauma. I've seen cranks that looked as if they had been raised from the Titanic that still worked just fine.

So....in answer to your question, you should replace your cranks every time they do that.

Last edited by slorollin; 06-07-14 at 08:33 AM.
slorollin is offline  
Old 06-07-14, 08:35 AM
  #6  
mulveyr 
Senior Member
 
mulveyr's Avatar
 
Join Date: Feb 2010
Location: In the wilds of NY
Posts: 1,568

Bikes: Box Dog Pelican, Raleigh Sojourn, Specialized Secteur, 1991 Cannondale tandem

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 39 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
They should be replaced every three years? Who told you that--someone who sells bike parts?

No, cranks can easily go tens of thousands of miles and more.
__________________
Knows the weight of my bike to the nearest 10 pounds.
mulveyr is offline  
Old 06-07-14, 08:36 AM
  #7  
gregf83 
Senior Member
 
Join Date: Jun 2008
Location: Vancouver, BC
Posts: 8,873
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 981 Post(s)
Liked 80 Times in 53 Posts
Failure rate for cranks is very low and can be due to a manufacturing defect. If there's a defect it can essentially fail at any time so changing them out after a couple of years is no guarantee you won't have a failure.

Given the failure rate is so low, I would not expect you to have another failure in your lifetime
gregf83 is offline  
Old 06-09-14, 09:55 AM
  #8  
pdlamb
Senior Member
 
Join Date: Dec 2010
Location: northern Deep South
Posts: 5,359

Bikes: Fuji Touring, Novara Randonee

Mentioned: 28 Post(s)
Tagged: 0 Thread(s)
Quoted: 1014 Post(s)
Liked 77 Times in 51 Posts
It's probably a good idea to inspect your cranks periodically, looking for cracks that might lead to breakage.

I guess I should do that, too; it's probably been three years since I looked mine over carefully.
pdlamb is online now  
Old 06-09-14, 10:05 AM
  #9  
Wilfred Laurier
Señor Member
 
Wilfred Laurier's Avatar
 
Join Date: Feb 2013
Posts: 4,497
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 399 Post(s)
Liked 99 Times in 71 Posts
i broke one crank at the eye
and it was a forty year old steel raleigh crank
otherwise
improper installation has resulted in failed crank tapers
and the end product is a crank that wont stay tight

but i have never snapped a crank in half

+1 that changing every crank every three years is complete bs
as is any maintenance rule that does not take into account usage details
Wilfred Laurier is offline  
Old 06-09-14, 10:18 AM
  #10  
Cyclosaurus
Senior Member
 
Cyclosaurus's Avatar
 
Join Date: Aug 2013
Location: Chicago Western 'burbs
Posts: 1,065

Bikes: 1993 NOS Mt Shasta Tempest, Motobecane Fantom Cross CX, Dahon Speed D7, Dahon Vector P8, Bullitt Superfly

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
From the look of the break (essentially flat across the entire cross section), of it the crank arm failed under pure tension. That arm should be capable of handling tensile stress of 10x your weight or more with no problem. I would contact the manufacturer.
Cyclosaurus is offline  
Old 06-09-14, 10:30 AM
  #11  
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 41,396

Bikes: 8

Mentioned: 188 Post(s)
Tagged: 0 Thread(s)
Quoted: 6921 Post(s)
Liked 245 Times in 203 Posts
Stress Risers , are started from scratches , and the scratch becomes a weak point,

flexing and metal fatigue work the weak point. ... its something even hard tempered aluminum is prone to ..


Ride hard, climb standing, sprint from stops?


http://en.wikipedia.org/wiki/Stress_concentration

http://www.engineersedge.com/materia...ntals_9902.htm

Last edited by fietsbob; 06-09-14 at 01:39 PM.
fietsbob is offline  
Old 06-09-14, 10:39 AM
  #12  
Wilfred Laurier
Señor Member
 
Wilfred Laurier's Avatar
 
Join Date: Feb 2013
Posts: 4,497
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 399 Post(s)
Liked 99 Times in 71 Posts
Originally Posted by Cyclosaurus View Post
From the look of the break (essentially flat across the entire cross section), of it the crank arm failed under pure tension.
this is 100% incorrect
but presented with such confidence
that i give you a B for effort
Wilfred Laurier is offline  
Old 06-09-14, 10:42 AM
  #13  
Sixty Fiver
Bicycle Repair Man !!!
 
Sixty Fiver's Avatar
 
Join Date: Sep 2007
Location: YEG
Posts: 27,266

Bikes: See my sig...

Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 46 Post(s)
Likes: 0
Liked 3 Times in 3 Posts
I guess I should be looking at replacing all the cranks on my bikes since they are all older than three years although to my good fortune, none have ever failed... this is gonna get spendy.

I wish someone had told me about that three year rule... I have been living on the edge without knowing it.
Sixty Fiver is offline  
Old 06-09-14, 01:24 PM
  #14  
rebel1916
Senior Member
 
rebel1916's Avatar
 
Join Date: Aug 2011
Posts: 3,026
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Liked 2 Times in 2 Posts
I'm guessing you droped the hamer and dialed it up to 400w.
rebel1916 is offline  
Old 06-09-14, 02:43 PM
  #15  
Little Darwin
The Improbable Bulk
 
Little Darwin's Avatar
 
Join Date: Jul 2005
Location: Wilkes-Barre, PA
Posts: 8,401

Bikes: Many

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by rebel1916 View Post
I'm guessing you droped the hamer and dialed it up to 400w.
I haven't seen that phrase pop up outside of the road forum in a long time.
__________________
Slow Ride Cyclists of NEPA

People do not seem to realize that their opinion of the world is also a confession of character.
- Ralph Waldo Emerson
Little Darwin is offline  
Old 06-09-14, 03:18 PM
  #16  
Dave Horne
Senior Member
 
Join Date: May 2014
Location: Vught, The Netherlands
Posts: 374

Bikes: Van Nicholas (Titanium) Deveron, Pinion 18 speed, Gates belt, disc brakes; Brompton - 5 speed Sturmey-Archer

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I've never had to replace a crank.
Dave Horne is offline  
Old 06-09-14, 03:44 PM
  #17  
MRT2
Senior Member
 
MRT2's Avatar
 
Join Date: Jun 2007
Location: Wisconsin
Posts: 5,866

Bikes: 2012 Salsa Casseroll, 2009 Kona Blast, 1997 Bianchi Advantage, 1994 Trek 930.

Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 829 Post(s)
Liked 3 Times in 2 Posts
I haven't changed out a crank in my lifetime. My wife owns a mid 70s Peugeot touring bike that still has the original cranks.
MRT2 is offline  
Old 06-09-14, 03:46 PM
  #18  
flatlander_48
Cathedral City, CA
 
flatlander_48's Avatar
 
Join Date: Oct 2004
Location: Cathedral City, CA
Posts: 1,503

Bikes: 2016 RITCHEY BreakAway (full Chorus 11), 2005 Ritchey BreakAway (full Chorus 11, STOLEN), 2001 Gary Fisher Tassajara mountain bike (sold), 2004 Giant TRC 2 road bike (sold)

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Wilfred Laurier View Post
this is 100% incorrect
but presented with such confidence
that i give you a B for effort
Agreed. The failure was in bending. Given that the pedaling load is applied to the crank as a moment due to the distance from the center of the pedal platform to the crank, it would seem to be difficult to get break in pure tension.

Also, it looks like there is damage on the remaining part of the crank. There appears to be a gash between the 5 (in 105) and the break. I would guess the dark portion of the break is the crack and the shiny part is what flexed just before it broke.
flatlander_48 is offline  
Old 06-09-14, 03:55 PM
  #19  
rebel1916
Senior Member
 
rebel1916's Avatar
 
Join Date: Aug 2011
Posts: 3,026
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 19 Post(s)
Liked 2 Times in 2 Posts
Originally Posted by rebel1916 View Post
I'm guessing you droped the hamer and dialed it up to 400w.
It's always appropriate. I even use in in the real world now and then.
rebel1916 is offline  
Old 06-09-14, 05:20 PM
  #20  
Sixty Fiver
Bicycle Repair Man !!!
 
Sixty Fiver's Avatar
 
Join Date: Sep 2007
Location: YEG
Posts: 27,266

Bikes: See my sig...

Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 46 Post(s)
Likes: 0
Liked 3 Times in 3 Posts
This crank is 59 years old... I did have to snug up a cotter pin... once.



Maybe a better example...

The Deore crank on my touring bike has well over 40,000 km on it... and is 27 years old.
Sixty Fiver is offline  
Old 06-10-14, 05:56 PM
  #21  
Pistard
Senior Member
 
Pistard's Avatar
 
Join Date: Aug 2011
Location: Columbia county, NY
Posts: 572
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 13 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Replacing a crank......... gotta go to Youtube for that, I must be lucky, got 40, 30 ,25 Year olds...
Pistard is offline  
Old 06-10-14, 06:12 PM
  #22  
Bandera 
~>~
 
Join Date: Mar 2013
Location: TX Hill Country
Posts: 5,936
Mentioned: 87 Post(s)
Tagged: 0 Thread(s)
Quoted: 1109 Post(s)
Liked 144 Times in 93 Posts
Originally Posted by oggyeater View Post
I have been told pedal cranks should be replaced every 3 years ish?! do they snap that often
Sheer utter nonsense.
These have been in service since 1977, on a fixed gear since 1992. I don't fret about their reliability in the least.
It might pay to inspect one's kit to prevent failure if one does a fair bit of crashing.....

-Bandera
Attached Images
File Type: jpg
Fixed_Trek.jpg (62.5 KB, 4 views)
__________________
'74 Raleigh Internat'l. '77 Trek TX900 FG. '90 Vitus 979. '10 Merckx EMX3. '13 Soma Stanyan
Bandera is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
mkansari
Bicycle Mechanics
33
10-02-12 09:54 PM
Suff
Bicycle Mechanics
10
08-28-12 06:06 PM
Dan Lester
Bicycle Mechanics
10
06-03-12 04:24 PM
gr8fzy1
Bicycle Mechanics
20
05-09-11 08:25 AM
mlau
Folding Bikes
16
04-12-10 03:33 PM

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.