Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

Crank has become wobbly on bearing shaft - replacement only solution?

Notices
Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

Crank has become wobbly on bearing shaft - replacement only solution?

Old 11-28-23, 01:06 PM
  #1  
Full Member
Thread Starter
 
Join Date: Aug 2020
Posts: 244
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 206 Post(s)
Liked 38 Times in 27 Posts
Crank has become wobbly on bearing shaft - replacement only solution?

One of the crank arms has become wobbly on the shaft coming out of the bearing, seems the machined area that goes over the spindle has gotten wallowed out enough to make it loose. Is there any common fix for this or is replacement of the crank arms the only option?

It's a VP BC-73 on a Trek Verve2.

Thanks.

Last edited by MyRedTrek; 11-28-23 at 03:20 PM.
MyRedTrek is offline  
Old 11-28-23, 01:41 PM
  #2  
I'm good to go!
 
Iride01's Avatar
 
Join Date: Jul 2017
Location: Mississippi
Posts: 14,565

Bikes: Tarmac Disc Comp Di2 - 2020

Mentioned: 50 Post(s)
Tagged: 0 Thread(s)
Quoted: 6006 Post(s)
Liked 4,632 Times in 3,194 Posts
There are so many different types of cranks and bottom brackets that without more details, all we can do is give general advice that might not be the most correct for your situation.

If the crank arms are loose on the spindle, then have you tried to tighten the crank arm bolt? If the crank arm bolt is tight, you might need a near crank arm. Or you might be better off with a entire new crank and BB.

What bike, what crank model and part number. Usually it's on the backside of the arm near the hole for the pedals.
Iride01 is offline  
Likes For Iride01:
Old 11-28-23, 01:53 PM
  #3  
SE Wis
 
dedhed's Avatar
 
Join Date: Apr 2005
Location: Milwaukee, WI
Posts: 10,449

Bikes: '68 Raleigh Sprite, '02 Raleigh C500, '84 Raleigh Gran Prix, '91 Trek 400, 2013 Novara Randonee, 1990 Trek 970

Mentioned: 39 Post(s)
Tagged: 0 Thread(s)
Quoted: 2701 Post(s)
Liked 3,304 Times in 2,008 Posts
Tighten the bolt/nut see if it takes care of it. If too worn out you can shim with beer can until you get a replacement arm. Arms are available as separate units so you can usually buy only the side you need.

The tapers come in both diamond and square orientation and crank arms come in different lengths (mostly 160mm-175mm). There is also JIS vs Iso taper.

https://www.sheldonbrown.com/bbtaper.html

https://www.sheldonbrown.com/tooltips/cotterless.html
dedhed is offline  
Likes For dedhed:
Old 11-28-23, 02:02 PM
  #4  
Habitual User
 
Eric F's Avatar
 
Join Date: Jan 2020
Location: Altadena, CA
Posts: 7,571

Bikes: 2023 Niner RLT 9 RDO, 2018 Trek Procaliber 9.9 RSL, 2018 Storck Fascenario.3 Platinum, 2003 Time VX Special Pro, 2001 Colnago VIP, 1999 Trek 9900 singlespeed, 1977 Nishiki ONP

Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 4699 Post(s)
Liked 7,595 Times in 3,592 Posts
Originally Posted by dedhed

The tapers come in both diamond and square orientation and crank arms come in different lengths (mostly 160mm-175mm). There is also JIS vs Iso taper.
...and Octalink...and Hollowtech II...and DUB...and GXP...
__________________
"Swedish fish. They're protein shaped." - livedarklions
Eric F is offline  
Likes For Eric F:
Old 11-28-23, 03:11 PM
  #5  
Full Member
Thread Starter
 
Join Date: Aug 2020
Posts: 244
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 206 Post(s)
Liked 38 Times in 27 Posts
Originally Posted by Iride01
There are so many different types of cranks and bottom brackets that without more details, all we can do is give general advice that might not be the most correct for your situation.

If the crank arms are loose on the spindle, then have you tried to tighten the crank arm bolt? If the crank arm bolt is tight, you might need a near crank arm. Or you might be better off with a entire new crank and BB.

What bike, what crank model and part number. Usually it's on the backside of the arm near the hole for the pedals.
VP BC-73 on a Trek Verve2

MyRedTrek is offline  
Old 11-28-23, 03:29 PM
  #6  
Banned
 
Join Date: Dec 2018
Location: Pac NW
Posts: 8,761

Bikes: '70s - '80s Campagnolo

Mentioned: 92 Post(s)
Tagged: 0 Thread(s)
Quoted: 3844 Post(s)
Liked 6,426 Times in 3,180 Posts
Originally Posted by MyRedTrek
... area that goes over the spindle has gotten wallowed out...
So, the crank arm's square taper has been deformed?

This is often the direct result of continued tightening of the crank bolt. Once the crank arm is installed and the crank bolt is tightened to the correct torque, you should not attempt to retighten the bolt.

If the crank arm's square taper is deformed, you need to replace the arm. Hopefully the problem is with the NDS arm, so you can simply leave the drive-side as is and find an inexpensive replacement with the correct arm length (165mm, 170, 172, 175, etc.)
SurferRosa is offline  
Likes For SurferRosa:
Old 11-28-23, 03:29 PM
  #7  
Senior Member
 
Join Date: Mar 2021
Location: SoCal
Posts: 3,092

Bikes: Cuevas Custom, Cimmaron, 1988 "Pinalized Rockma", 1984 Trek 510, Moulton custom touring, Raleigh Competition GS, Bridgestone Mb-2 & 3, 1980's Peugeot - US, City, & Canyon Express (6)

Mentioned: 25 Post(s)
Tagged: 0 Thread(s)
Quoted: 1008 Post(s)
Liked 3,383 Times in 1,689 Posts
If you tighten the bolt and that does not solve the problem, then take the bolt out and inspect the Crank arm and Bottom bracket for wear. More likely the crank arm would be worn/deformed, as folks said above, then time to find a replacement. Check for specs on inside of crank arm and then ask here or go search ebay, you can just replace the one arm easily, or get a full set of cranks that fits your bottom bracket.
SoCaled is offline  
Likes For SoCaled:
Old 11-28-23, 07:48 PM
  #8  
SE Wis
 
dedhed's Avatar
 
Join Date: Apr 2005
Location: Milwaukee, WI
Posts: 10,449

Bikes: '68 Raleigh Sprite, '02 Raleigh C500, '84 Raleigh Gran Prix, '91 Trek 400, 2013 Novara Randonee, 1990 Trek 970

Mentioned: 39 Post(s)
Tagged: 0 Thread(s)
Quoted: 2701 Post(s)
Liked 3,304 Times in 2,008 Posts
Originally Posted by Eric F
...and Octalink...and Hollowtech II...and DUB...and GXP...
Reading between the lines and having been on BF awhile you get a feel for what the OP is describing, and the description of the problems leaned (correctly) toward square taper .
You rarely hear of loose crank arm issues on 2 piece cranks and even not often on Octalink, power spline, gigpipe, and other variations on 3 piece cranks.
dedhed is offline  
Likes For dedhed:

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

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

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.