Crank has become wobbly on bearing shaft - replacement only solution?
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.
It's a VP BC-73 on a Trek Verve2.
Thanks.
Last edited by MyRedTrek; 11-28-23 at 03:20 PM.
11-28-23, 01:41 PM
#2
I'm good to go!
Join Date: Jul 2017
Location: Mississippi
Posts: 15,001
Bikes: Tarmac Disc Comp Di2 - 2020
Mentioned: 51 Post(s)
Tagged: 0 Thread(s)
Quoted: 6197 Post(s)
Liked 4,814 Times
in
3,321 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.
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.
Likes For Iride01:
11-28-23, 01:53 PM
#3
SE Wis
Join Date: Apr 2005
Location: Milwaukee, WI
Posts: 10,517
Bikes: '68 Raleigh Sprite, '02 Raleigh C500, '84 Raleigh Gran Prix, '91 Trek 400, 2013 Novara Randonee, 1990 Trek 970
Mentioned: 40 Post(s)
Tagged: 0 Thread(s)
Quoted: 2747 Post(s)
Liked 3,401 Times
in
2,058 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
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
11-28-23, 02:02 PM
#4
Habitual User
Join Date: Jan 2020
Location: Altadena, CA
Posts: 7,997
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: 4957 Post(s)
Liked 8,099 Times
in
3,833 Posts
...and Octalink...and Hollowtech II...and DUB...and GXP...
__________________
"Swedish fish. They're protein shaped." - livedarklions
"Swedish fish. They're protein shaped." - livedarklions
Likes For Eric F:
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
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.
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.
11-28-23, 03:29 PM
#6
señor miembro
Join Date: Dec 2018
Location: Pac NW
Posts: 6,627
Bikes: '70s - '80s Campagnolo
Mentioned: 92 Post(s)
Tagged: 0 Thread(s)
Quoted: 3890 Post(s)
Liked 6,491 Times
in
3,213 Posts
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.)
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.)
11-28-23, 03:29 PM
#7
Senior Member
Join Date: Mar 2021
Location: SoCal
Posts: 2,308
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: 26 Post(s)
Tagged: 0 Thread(s)
Quoted: 1105 Post(s)
Liked 3,767 Times
in
1,845 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.
Likes For SoCaled:
11-28-23, 07:48 PM
#8
SE Wis
Join Date: Apr 2005
Location: Milwaukee, WI
Posts: 10,517
Bikes: '68 Raleigh Sprite, '02 Raleigh C500, '84 Raleigh Gran Prix, '91 Trek 400, 2013 Novara Randonee, 1990 Trek 970
Mentioned: 40 Post(s)
Tagged: 0 Thread(s)
Quoted: 2747 Post(s)
Liked 3,401 Times
in
2,058 Posts
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.
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.
Likes For dedhed:
