Bought a Cannondale Quick SL3 about a month ago and really like it. Do have a question about shifting gears that has me perplexed. When in the middle gear range (I have 27 gears) and coming to a hill I shift down many times to the lowest gear level. The Shimano Deore 9 speed Rear Derailleur shifts smoothly up or down but on several occasions when I shift down to the lowest gear (in mid range 2) I get a sudden jerk between the lowest gear in the range setting and then into some other lower gear when I depress shift bar one more time. And this is only using the shifter on the right side.

Hard to explain but when shifting I can tell by the tension of right side shifter arm that I've reached the lowest gear. But when I shift one more time the shift armr (on handle bar) pushes in half way and then chain momentarily slips and I'm in a lower gear. There is also tight tension on this last shift and and as I mentioned the shift arm does not fully click in - only goes half way while I'm pedaling. Starting to wonder if I should even be trying to shift down to this last gear level (since shifter arm and Derailleur don't seem to like it). This last lowest gear though (in mid range) does help me climb hills without shifting down to the lowest range setting - range one.

I'm some what of a newbie so not sure if this is standard slippage when shifting to the lowest gear (in the mid range section). All other shifting levels work find, so maybe I'm being a little to picky in my old age, but feel a good Derailleur should not slip in any gear setting.

Is this something my bike dealer can fix or repair during my warranty period?

The dealer should have told you to go back to the store after about a month to get the gear / brakes adjusted, normally there is some cable stretch in new cables, this is probably what you are experiencing.

I'm no expert, but you may be crossing the chain too much. Instead of leaving it in "2" and dropping all the way to the lowest gear, try going to "1" on the left (front chain ring) and "2 or 3" on the right (rear cassette). Find the combination that does not cross the chain so far but work for the climb you need.

I think jimc101 and DocsDad are both right;you prolly need the cable tweaked,and you really shouldn't go below 3rd in the middle ring.

At my clinic,I explain to people that the front rings are basically low,medium,and high gear range,and that they should be matched to the gears in the back.

left right
1 1-4
2 3-6
3 5-9

Yes, I would concur with this. It gives me a buzz when I do a double shift - as in going from 1/4 up to 2/3, so going up on the front and down on the back at the same time, but I know I'm looking after my machinery.

I really doubt that this is a chain crossing issue. That is almost non-existent with modern drive trains. It sounds to me like you've had some cable stretch, which is normal for a new bike that's still "breaking in". Take it to the dealer, have them adjust your shift cables and anything else that may need adjusted, and you should be good to go again for quite a while.

Certainly you could be right. However, it is a possibility. I have experienced this on a few 8 speeds and can only imagine the 9 speed would be the same (or worse). It tends to not like to stay in gear when dropping that low from the large or middle ring. Obviously, the nice thing about a wide range of gears is the overlap to make accommodations for this issue.

Anyway, just another possibility.

What is an example of a modern bike that does not have a chain crossing issue?
Mine is only a few years old and if you go past #4 on the back you will begin to rub on the front derailler unless you go to #2.

Sounds like a cable tension issue. If you don't know how to adjust this yourself, a bike shop will do it for you in about two minutes. Alternatively, it's possible the "stop" screws on the rear mech need adjusting. Again, this is a two-minute job. Worth getting someone to show you how to do these things, they're very easy.

I'd be surprised if the problem described is a result of cross-chaining. Cross-chaining might result in noisily fouling the front mech, but is less likely to give rise to it being difficult/impossible to shift at the rear

Single speed or internal hub.

Seriously,most modern bikes have cassettes that are wide enough that this can be an 'issue'. I put that in quotes because proper shifting technique pretty much makes this a non-issue.