Originally Posted by
carpediemracing
I didn't quite grasp why it wouldn't be the smaller lever bumping against the bigger lever (the braking lever). Usually it rattles if it's no longer aligned with the bumper.
You can buy tiny rubber bands (like for braces) and wrap it around the big brake lever at the point of contact. Other things works too but that one seems pretty efficient and simple.
cdr
The reason I don't think it's the shift lever is that when I hold it stationary the rattle is still present. Since I like to spin, I mostly ride the 39 ring so the left shifter rarely gets used but it rattles on the 53 as well.