General Cycling Discussion - Shift question

My wife and I love our 2003 Gary Fisher Tassajara's, and have so far only put about 15 hours on them. The LBS said when they get about 30 hours on them to bring them in for a tuneup. This weekend we took a 35 mile ride along the Schulkyill river trail near Philadelphia PA. (mostly pavement and/or gravel-packed dirt) and my wife complained several times that when going uphill or really cranking on the pedals, the bike was shifting on it's own without touching the shifters (Shimano Deore quick shifts) Before I take it back to the LBS, what should I adjust to prevent the unexpected shifts?? Is it the derailler or the actual quick shift that is probably causing the problem??? I'm pretty mechanically inclined (been away from bikes a number of years though) and was hoping you enthusiasts could help me out before I take it back to the LBS....Thanks

Since the bike is new, it's probably the derailleur indexing that needs to be adjusted. See Sheldon Brown's article (http://sheldonbrown.com/derailer-adjustment.html) on the subject (point #3).

Regards,

Thank you ,....I'll follow the advice.

I would be surprised if it is the indexing. New cables settle in, sometimes called stretch, and develop slack, almost always causing some kind of shifting problem. This is exactly why the LBS told you to bring them back for adjustment. Don't try to adjust it yourself unless you know what you are doing. Right now it is probably just a matter of taking up the slack. If you start turning things it will take the LBS longer to straighten out.
FWIW,
Raymond

It is the cable stretch which causes the indexing problem.
Sometimes you can take up the slack with the various cable stops, but often you have to pull the whole cable a bit tighter.
Your LBS should do that free, its a 2 min job if you know how, and ther best way to learn is to watch a decent mechanic do it.

Dont touch the two limit screws on the derailleur mechanism, these are NOT affected by cable tension.

aww...so cute, matching "he" and "she" bikes...

If you want, you can probably just drop by the LBS and say "hey, we're not ready for the 30-hour check yet, but I think the cable stretched a little... can you touch up the indexing?" It only takes them a moment to put it in the stand, eyeball the derailleur for proper alignment (ie, not misaligned due to a fall or something) and take out the cable slack.