This may seem counterintuitive; don't all four brakes work to stop the car? Yes. But the front brakes do most (about 70 percent) of the stopping, chiefly on account of the fact that when you apply the brakes, the weight of the vehicle shifts forward; that's why front brake pads wear out sooner than rear brake pads (or shoes, if your car has drum rear brakes).

And that's why you ought to remember to check – or have someone else check – your front brakes first.  How often? Brake pad life varies from vehicle to vehicle and driver to driver, because there are many variables, including your braking habits – but as a general rule, a set of new pads should last about 30,000 miles.