Imagine if you will that you are a set of bottom bracket bearings in your bicycle. Sounds like a simple job really. You'll get to go on some killer rides with your only responsibility being that of spinning in circles while supporting your good friend and neighbor... the crankset. You'll get to ride all the killer trails, probably travel to exotic locations and maybe... just maybe help your rider stand atop the podium at the local mountain bike race. Ahh, I can smell victory from here!!!
After some time at this "life" you'll probably start to realize that it's not all buff singletrack and long warm summer days. The first of the "rough days" might start with a trip to Downieville early in the season with multiple stream crossings followed by a ride atop a car at 80mph in the rain. The next ride might be an all day epic in the late summer with a group of buds where you'll be stuck behind other riders for most of the day eating more dust than you imagined ever possible. Then there's winter. Don't tell me you've never ridden in the snow. Oh... did I mention that you're "owner" might be a 200lb gorilla of a rider with a propensity for riding 5 days a week, thinks that all bikes make grinding noises from the bottom bracket and has a riding style that's described by his riding partners as ANYTHING but smooth.
Bottom bracket bearings have changed drastically over the years and will probably continue to do so as the industry strives to build a better mousetrap. The bottom bracket bearings live between the crankarms of your bike and take quite the beating during a typical day of riding regardless of rider weight, strength and/or technique. Although many variations exist, it's the "external bottom bracket" that we're going to hone in on this time around. External BB's have been widely accepted by all the "players" in the industry and regardless of the name on your crankset there's a good chance that it has external bearings which can and will fail at some point in their/your life. Fortunately for you and your bike there's a fix for the creaking, squeaking or whatever else might be going on in there and it comes in the form of aftermarket bearings. Mighty Mobile put some bearings on several riders bikes to see how they stood the test of time and after a year of positive results we started placing orders for the bearing kits in the masses. I won't bore you with too much technical mumbo jumbo and simplify things by saying that the aftermarket bearings come with a larger diameter bearings and a secondary seal (most of the time) that will keep your steed running smooth for longer than the stock bearings. But wait - just like buying something off of late night TV - THERE'S MORE!!! Things get even better (most of the time) when it comes to paying the bill. When you replace the bearings and reuse the existing bearing cups you'll be saving yourself some hard earned $$!!
First, out with the old.
Close up shot of the bearing without the crankset. Dirty huh.
It's a nasty environment down there. Notice the grime on the spindle.
This is what your bottom bracket (half of it anyhow) looks like out of the bike. The silver part is the bearing cup and the black piece is a seal. 
Inside the frame. Yep, that's water in there.
With these tools...
... we can go in here. Muwhaahaaa. (to be said sinisterly... like Dracula)
The bearing has already been pressed out of the cup. With the inside of cups that look like this....
.... it's no wonder that your bearings probably look like this.
So, at this point you can either buy a complete bottom bracket or just replace the bearings with a new set. How'z 'bout saving yourself some hard earned $$ and just press new bearings in the existing cups. The cups typically clean up just fine. See.
Tahdah! New bearings. I can almost feel the smoothness from here. 
Let's clean up some more stuff like the spindle and the inside of the frame. Look Ma... no more grime!
Almost back together. Damn that bearing looks good doesn't it!
Wait. We're not done yet. How about another seal. Yeah... let's hear it for another seal!!!
You feeling warm and tingly yet? Me too!! Mighty Mobile carries bearing upgrades for most popular makes and models. Ceramic and ceramic hybrids also available. And just like everything we do, it's done at your house, on your terms and done right the first time. Call anytime to schedule an appointment.
With these tools...
.... it's no wonder that your bearings probably look like this.
So, at this point you can either buy a complete bottom bracket or just replace the bearings with a new set. How'z 'bout saving yourself some hard earned $$ and just press new bearings in the existing cups. The cups typically clean up just fine. See.
