Shimano G03S Disc Brake pads

On average, brake pads should be replaced every 25,000 to 65,000 miles, while rotors typically should be changed anywhere from 30,000 to 70,000 miles.
However, the exact number can differ depending on driving conditions and styles.

If your brake pads are near the end of their useful life, the first symptom you'll begin to notice is a squeaking or squealing noise coming from the brakes.
Squealing brake pads are typically caused by excessively worn down pads. Once you've worn down your pads enough you'll start to experience a grinding noise, at which time you'll also begin to damage your rotors, making the cost of repair even more expensive.

Like we stated above, if you're experiencing a grinding noise while you're applying pressure to the brake pedal, your brake pads need to be replaced ASAP. Some brake pads have built in metal wear indicators, which are designed to make a loud noise and alert you that it's time to replace the pads. If you leave the brake pads to continue grinding, you're opening yourself up to a lot more damage and higher repair costs.

Vibration when you apply the brakes is another sign that your vehicle's braking system is in need of professional help. Chances are that your rotors are warped and created uneven brake pad wear at the same time.

Another major sign that your brakes need to be checked out is loss of performance when applying the brakes. If you're
experiencing less than ideal stoppage times while applying your brakes, it may mean your brake pads are worn down completely or that your brake fluid is low (often times due to a leak). For a true understanding of what's going on with
your brakes, you'll want to get to a brake mechanic as soon as possible to ensure you don't lose all braking abilities.

Most modern vehicles come with brake warning lights that appear on your dash. One is your Antilock Braking System (ABS) light and the other is your brake system warning light. Your brake light won't always come on when there is an issue — it's also the light that appears on your dash when your parking brake is engaged. But if you're seeing a brake warning light and your parking brake isn't engaged, it's time to have a brake expert take a look at your system to diagnose your issues.

One way to easily check on your brake pads is to visually inspect them for wear. To do this, look between the spokes of your wheels and locate your brake pad. If it appears to be less than a ¼ inch or 6.4 mm thick, you're probably due for a set of new brake pads.