Bottom Bracket Removal

eFred

Finding my (electric) wheels
Jul 21, 2020
11
1
I have a mountain bike I'm planning to fit a bafang mid drive to. I have a 20 spine key to remove the bottom bracket but it doesn't fit. It appears to be a plastic fitting. How do you work out which key you need to remove it?
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
6,944
2,674
Basildon
Plasic ones are normally standard Shimano-type BBs with 20 teeth. You know that one side has a left hand thread. From memory, you undo both sides in the direction of forward pedalling.

Sometimes the fit is very tight. You might have to tap the tool in.
 

eFred

Finding my (electric) wheels
Jul 21, 2020
11
1
Thanks, think I'll have to find the right key now I know what to ask for as the one I've got isn't going to fit even with a very large hammer!:D
 

Woosh

Trade Member
May 19, 2012
14,989
12,270
Southend on Sea
wooshbikes.co.uk
some plastic cups are hard to shift.
The left side, non drive side, has normal thread, first to be removed.
The right hand side, drive side, is also called the fixed side because the cup is permanently connected to the right hand ballbearing, has left hand thread (reverse thread) and to be undone last.
You may need this tool to hold the removal tool securely to the bottom bracket's axle.


You can use a long M8 bolt or a crank bolt to do the same.

I have a 2ft long tube to extend the spanner and sometimes have to push the tube down with my foot.
 

eFred

Finding my (electric) wheels
Jul 21, 2020
11
1
Managed to modify the key I had with an angle grinder so now it fits. Decided I had nothing to lose as it didn't fit anything else I had! Made the grooves between the splines a bit deeper and now its a snug fit. Thanks for the help.