Bottom bracket repair/replacement

[Jimny14]

I've got a bike I'm using to learn about doing up bikes and repairing etc so that I can be better at it especially if I ever get a decent bike I don't bugger it up trying to fix it.
Now the bottom bracket has some play in it and I want to replace it with a new one and see if the old one is repairable as a project. Now first question is sourcing a new bottom bracket, I know there are different sizes etc but other than that I'm a bit stuck at identifying exactly what I'll need. The bike is early 80s and the BB is by sungio. Do I need to take it out to find out what I need?

 

[torqueless]

Re:

Do you have access to dedicated crank removal tools and BB spanners?

Chances are your BB is English thread, and if it is, the drive-side cup has to be turned clockwise to release it. The non-drive side is 'normal' i.e. you turn it counter-clockwise to release it. There is usually some numbers on the outside faces of the cups telling you what the thread is. You might not be able to read them until you've got the cranks off.

BB spindles come in different lengths to achieve proper chainline with whatever other components you've got. Some of the spindles are symmetrical, some ain't- those that ain't are usually longer on the drive side. Again there is usually some stampings on them telling you what they are, but yes, you need to get the spindle out to read them.

 

[Jimny14]

Thanks for the reply, time to crack out the torque wrench and BB removal kit, hope there are some useful numbers on it when I get round to it.

 

[darylw357]

RJ The Bike Guy has plenty of great videos on bottom bracket servicing/replacement.

[youtube]https://www.youtube.com/watch?v=yrkqf91H_Zk[/youtube]

As others have said, your key parameters are axle length, crank mounting type, and bb thread size.