Rubber Bumps In The Grooves Of Your Tire Tread. These little rubber bumps are so inconspicuous, you might never notice them unless checking the tread on your tire. Oddly enough, that is exactly what they are meant for. The little-raised edges inside the grooves of your tire’s tread are there to let you know when it’s time to change your tires. While many people still rely on the old penny head trick, an easy way to tell if you need to get to the tire shop is if the edges of your tread are even with the bumps. If they are, then you are driving on legally unsafe tires. If the edge is above that of the bump, you’re good to keep cruising for a while.