New Bike Cable Stretch Question

[Velocivixen]

I bought my Cross Check on July 16th and rode it about 150 miles by the time it had it's 1 month free tune up at the LBS where I bought it. So I've had it almost 2 months and it's got at least another 100-150 miles on it in the past month (250-300 total). It has a compact double chainring set up. I was in the small chain ring in the front and middle cogs in the back (maybe toward the bigger cogs a little), when I came to a stop on a 1-2% slow, short hill. I took off from my start, was under slight load when I shifted from small to large chainring and the chain shot past the large chainring and got caught between the chainring and my lovely chainring guard. I could not pedal, so coasted to the side of the road (I had taken the lane and there was a car behind me, but we were going slowly). I moved my bike onto the sidewalk where I could not pull the chain out, so I flipped my bike upside down on the lawn, pulled out the part of the chain that was stuck, pedaled and voila - chain and chain rings were playing nicely. Took all of about 30 seconds. On the way home I did some shifting in the front while on the flats with no problems whatsoever.
I think this was most likely due to cable stretch as the bike is still "new". Wondering what you think? I realize you shouldn't shift under load, but it's not like I was grinding up some epic hill. I probably should have shifted in the rear cogs if I had to shift at that moment since the distances aren't so significant and the chain is going "downhill" so to speak.
Anyway I'm having fenders mounted tomorrow and will have my LBS (not the one I bought it at) check/adjust the derailleurs, etc.
I appreciate any insight. Please....educate me...I'm a sponge just slurping up all the juicy knowledge here.

[KnottedYet]

Sounds like a limiter screw adjustment issue?

(there are two on the derailleur - one keeps the chain from overshooting the small ring and falling off to the inside, one keeps the chain from overshooting the big ring and falling off to the outside)

[Velocivixen]

Thanks Knotted. Yes that's what I was thinking, but since it only happened once I wondered if it were just the circumstances under which I was shifting or was it more cable stretch, or a combination of both? I have adjusted this very limit screw on day 2 of owning the bike when I dropped the chain 3/4 times shifting from small to large chainring! Mind you this was a brand new bike at that time, so you can imagine I was p*ssed! They should have more thoroughly checked things out before letting me walk out with it.
Anyway, thanks for your quick reply.

[DebW]

Knot is right - limiter screw. Chain stretch would cause the derailleur to not shift to the big ring. Put the chain on the smallest cog in back and the big cog in front. Then look at how close the chain is to the outside plate of the front derailleur. If the adjustment is correct, the chain should have only about 1 mm of clearance.

[Velocivixen]

Thank you both. I know which screw is the high limit screw but when one says to "tighten" it as did all the online articles it assumes I know which way to "tighten", so initially I turned the screw counter clockwise, which caused the chain to fall off again, then remembered "righty-tighty, lefty-loosey". I turned it clockwise and it's better now. I will still have the LBS mechanics, who from this shop I trust, check and make adjustments.
Thanks to you both.

Why would this happen just after two months? Do limit screws come loose?

[Velocivixen]

Oh, the reason I had to look it up online for additional help is because when I turned the high limit screw I didn't really see the derailleur cage move inboard or outboard.

[Bike Writer]

Why would this happen just after two months? Do limit screws come loose?

If I look at your earlier post this happened on day 2 originally so I don't think it's "coming loose" it sounds like it was not set right from the get go...good idea to have a pro check it out, especially one you trust...he/she will give you guidance about that.