Here's how you can check your brake pads yourself.

The brake pad consists of two flat pieces bonded together. One is called the "backing plate" and is a piece of metal about a quarter of an inch thick. The other, the stuff between the backing plate and the rotor, is called the "pad material", and this is what wears out.

When brake pads are new, the pad material is about 11 mm thick. When the pad material is about 2-3 mm thick, it's time to replace the pads. If it gets that thin, you will start to hear a squeaking sound (which you might hear even when you are not stepping on the pad), which is a metal tab on the inside pad that starts to come into contact with the rotor when the pads are that thin.

On the ITR, you can look through the spokes of the wheels and see the top edge of the outside brake pad, even without taking off the wheel. If you're not sure about how to do this, ask your favorite "car nut" to show you. Most such folks can show you how, even if they're not familiar with the ITR. Just show them these instructions.

Stand above the wheel, looking down through the spokes of the wheel to the top of the caliper (the big metal holder on the side of the rotor, which is the big metal disk inside the wheel). A flashlight will help. At the top, inside the caliper, you will see the edge of the brake pad - the metal backing plate and the pad material.

This method isn't totally thorough to check for worn pads, because sometimes the inside pad (which you can't see through the spokes of the wheels) wears slightly faster than the outside pad, so if the outside pad looks plenty thick, you would still need to remove the wheel to be totally thorough about it. But if the top of the outside pad is worn down to a thickness of about 2-3 mm or less, then you know that it's time to replace the pads.