Has anyone ever had to change a mountain bike part?  This can be fun but also time consuming.  I recently changed my tires on my MTB.  First I had to take the wheels off the bike.  Then I had to take the old tires off.  Finally I put the new tires on.  It took a little time to seat them properly. 

The final end result was just what I wanted.  new tires on my MTB made a difference on the trail.  It took a little time in my afternoon to do this but it was well worth the effort.

So if you are going to change any of your mountain bike parts plan out your job and consider the time needed to do the job.