I took my brand new CX3 out for it's first ride yesterday (besides up/down the block), and multiple times (at least 5) it would just shift on it's own? Is this normal and just a part of breaking it in?
Also, when I did shift, often times it had problems settling into the gear, and would go back/forth between two gears before settling on a gear?
Should I continue to ride it and let it break in, or stop until it can get looked at?
Thanks for the question! It sounds like we've got a cable tension issue! This is not uncommon at all, and the fix is typically quick and easy!
If the cable tension isn't set quite right, the position that the shifter moves the derailleur to won't align with the cogs in your cassette, and the chain will try to bounce back and forth between cogs.
It will work best if you've got somewhere you can securely hang the rear of the bike so the back tire is off the ground and you can spin the crank by hand to drive the back wheel- although you can do this while riding, it will just take a lot of start-stop-adjust-check-repeat steps.
While spinning the crank by hand as if you were pedaling at a mellow pace, use the barrel adjuster (the little knob that the cable travels through as it enters the derailleur) and turn it clockwise or counterclockwise until the noise and phantom shifting stop. You'll have to play with which way to turn it to make the noise stop. When the noise stops, doublecheck the shifting by hand-turning the cranks and using the shifter to shift up and down the range of gears.
I hope this helps! If you have questions or if this doesn't resolve the issue, please feel free to reach out to firstname.lastname@example.org - we've got a team of dedicated technicians who are here to assist with this stuff!
Does the bike have a quick-release rear hub? If so, it may be good to check that the axle is completely seated in the dropout and the skewer is properly closed. It's unlikely to be a culprit, but it's a good thing to quickly rule out.
I have exactly the same problem. Just got my Cannondale Quick CX3 delivered and it skips between rear gears, especially when using the smaller chainring. Can't take it to the local store since they're all closed. Hope the advice to adjust tension works for me too. Otherwise, the bike is almost unusable.
I'd agree that for a new bike it's probably the cable tension, also known as the indexing. But rather than simply guessing which way to turn the adjuster, this video has great visuals on adjusting rear shifting that gives a great deeper understanding of the mechanism: https://youtu.be/UkZxPIZ1ngY