I believe the material specification says ripples should expand after a completed tap (touch down and up). Right now they start and expand on touch down which means when I scroll the stocks app, I see ripples where I grab the list. See the polymer material design page on mobile to see what the expected behavior is: https://www.polymer-project.org/0.5/docs/elements/material.html#touch-ripple-effect