MTB: my rear derailleur is jumping gears too often....upgrade or adjust?

Question

I have a Gary Fisher Piranha that I have really enjoyed over the last few months, but in the last few weeks it has started to jump gears whenever I apply more than moderate force on the drivetrain (ie. standing up and cranking, for example)...it began with a 3(large front cog)-5 configuration, so I asked the trek bike shop guys and they said I was cross chaining it with this configuration, and that the middle front cog would allow me full range of the rear cassette....now, however I can be in the middle of both cassettes and it will jump on me when I stand up to crank over a little embankment or something....I ride this bike everyday day and go trail riding atleast 2 or 3 times a week....should I be performing some kind of maintenence that I have neglected to perform, or do I need to upgrade to better derailleurs and drivetrain components (right now, the derailleur system is SRAM X-5)? also, since I am 230lbs (and losing), is the sheer force I am applying when I sprint just too much?

Answer 1

just adjust your derailleur

Answer 2

I'm going to assume that being you have said "over the last few months" that this is a new bike. This being the case you have what happens to every new bike owner your cables need to be re-adjusted. A minor correction on the barrel adjusters should fix this problem.

Here some help:

http://sheldonbrown.com/derailer-adjustm...

Answer 3

I agree....if it's a new bike, it might just be cable tension...that's a very simple and common adjustment.  

Since it's a new bike, the chain probably isn't worn, which can cause some of that skipping.   If you've had problems binding up the chain or have been really mashing the pedals hard, then look carefully at the chain (sighting from rear to front on the top side) to see if it's twisted or has bent links.  Then, rotate the pedals backwards while watching the chain pass through the derailleur pulleys and/or the chainring teeth....if you have any stiff links, you'll see them raise up a little as the chain rotates.   Those can be fixed with lube, hand pressure, or a chain tool.  

Also, if you ever crashed or took a hit to the derailleur side of the bike, the hanger might be a little tweaked.  A shop can check this for you with the appropriate tool for a few bucks, and adjust it if necessary (lots of people overlook this very important thing).  

Even cheapie derailleurs work pretty well these days, so you probably don't need to upgrade unless you really want to.  And, you weren't cross-chaining the gears in those combinations.....3x5 is just fine.  The problem is elsewhere, obviously, as you figured out.  

Hope this helps.....if you need more, just post up again.   :o)