Replace Bicycle Crank Bearings

My daughter's new-ish bike started making grinding sounds and pedaling rough.  I took it apart and the bearings in the pedal system were shot.  Really rough shape.  My wife was going to take it to the bike shop and see if it was an inexpensive repair.  
I saw a junk bike in the trash on my way home from work.  Snagged it, took it home, took it apart, and was happy to find that the bearings LOOKED the same.  So I used them as replacement parts... and they fit!  Bike seems fine now.  I was happy, as I am not mechanically inclined.  I probably only saved $20 in the grand scheme of life, but I was able to take something out of the trash and use it to fix something at home.  The rest of the bike will probably go to the scrap yard this summer with the next load, so it will stay out of the landfill too!

I don't know if there is an underlying problem that will make the new bearings wear out... but I can cross that bridge another day.  It was a new bike, so it seemed odd that they wore out like they did.  

Note: the good bike and the donor bikes were different brands, styles, and sizes from each other, yet seemed to have the same bearings.  I love it when things are simple-ish and parts are redundant.  Makes home repairs much more do-able.

Thomas Dean wrote:My daughter's new-ish bike started making grinding sounds and pedaling rough.  I took it apart and the bearings in the pedal system were shot.  

YAY! Bicycles are too useful to be trashed!
In my experience, the bearings wear out quickly due to lack of a good grease. I tend to start any new bike by opening it up and putting a good solid black heavy grease in there. I have only needed to change the bearings once, but it was on a old bike, in the early 80's, that was well used when I got it, and I put many many miles on it before having to change them. The newer bikes quite possibly have a less hard metal used in the bearings, or come with a cheaper grease in them.

Cool! Good skill to have!! Congratulations!
:D

Pearl Sutton wrote:
In my experience, the bearings wear out quickly due to lack of a good grease. I tend to start any new bike by opening it up and putting a good solid black heavy grease in there. I have only needed to change the bearings once, but it was on a old bike, in the early 80's, that was well used when I got it, and I put many many miles on it before having to change them. The newer bikes quite possibly have a less hard metal used in the bearings, or come with a cheaper grease in them.

I soaked my donor bearings in used motor oil then wiped them down.  I put a bit of the grease we use on farm implements on the bearings, but I did not go nuts with it, as I don't want it making a mess if it oozes out.  My kids are prone to messes already, grease is a pain to clean up.  Should I open it back up and put more grease on them?

I have always gone nuts with it. Think packing car wheel bearings (look it up if you don't know about doing it.) You pack all of the air space with grease. The idea is no air space means no water, no dirt space. So I pack all bearings solid, really work it into the cracks, and it seems to work well for me.