Just as with a car, your bike (or in this case mine) requires routine maintaince.   Over time routine maintenance (keeping your chain clean and lubed) stops being enough.  My Mountain bike recently reached this point.  It started when the mechnanism in my rear hub started to not spin freely.  I needed a new rear wheel.  Unfortunately the first mechanic I took my bike to told me my problems weren't significant and all I needed to do was repair a broken spoke...  On my next ride out my rear wheel truly died - when I tried to pedal under stress the hub's inner workings were stripped and I went no where.

Well I spoke with the mechanic again and he said yep - you need a new rear wheel, plus my chain was worn as were both my front and rear chain rings.  I was going to need a new wheel and a new crankset - which he would have sold me, but I passed.  After all we're talking about a bike that cost me less than $400.  I searched for and found a good deal, getting a new pair of wheels (that are disc brake compatible - as is my frame) for about $50 (sales aligned and I got about 75% off the retail from this one store).  So I learned to disassemble my rear chain rings from the wheel and transitioned the wheel on my own, allowing me to continue - at least for one ride.

On that ride I snapped my chain - not the first time I've done this.  Replacing the remainder of my drivetrain started when I snapped my chain.  When I put a new chain on the bike I immediately started suffering from what is known as "Chain Suck". Chain suck is characterized by your chain remaining on your front chain ring as you pedal, so instead of it coming free at the bottom of your chain ring and feeding to the back wheel, the chain rides back up and runs into itself coming onto the top of the chain ring.  This stops your pedalling.  Chain suck normally occurs on your small front chain ring and accordingly mostly strikes when you are trying to climb.  It's a significant problem and since it started on my first ride with my new chain it meant I needed more work.

Recognizing that the problem was that my front chain rings were just too worn, I set out to replace them.  Did I need to purchase a whole new front crankset for like $200+?  No.

Fortunately I realized I didn't need to spend $200+ on a new crankset and instead could replace only the chain rings keeping my front cranks.  So instead of paying $200 for a new front crankset I paid $18 for a small chain ring and about $32 for a medium (middle) chain ring.  Throw in a new rear cassette for good measure at $40 and you are talking about rebuilding the key elements of my drive train from about $100 instead of $250 + labor.

So how worn were my components well here are some photos to compare the rings first up my old small front chain ring, then the reassemble crankset with small and medium rings and then the old medium chain ring:

Can you spot how warn my chain ring teeth were.  As you can tell I've been pushing my bike pretty hard and it shows on those rings.  I also replace my rear cassette and here is the reverse angle of my old and new rear cassette, again note how worn the old teeth are:

even though it's clean, you can see how worn the teeth are and how uneven the curves are in the old cassette above vs. the cassette below:

So all told I put in about $150 to rebuild the majority of the drive train elements on my bike.  Doing the work myself saved literally hundreds more in maintenance charges considering the going rate for a simple tune up in Southern California is $50.  The result my bike is once again operational and although I'm still hoping to one day pull down a beautiful full suspension bike (like everyone I ride with) for now my hard-tail is trail ready and I can continue to enjoy views like this one from the top of 2N71.