Do worn out brake pads give off any warning, like a squeal?

Just wondering if I get a warning from my brake pads? Can you really see how much pad you have left?

 

Squeaking can be a sign of worn pads but "grinding" noises are definitely a bad sign. Most front brake pads are easy to get a peek at and are kind of like a tire, they have a wear indicator. The pads have a little "notch" in them and when the notch is at the same level as the main pad you need to replace them.

 

I've never heard any noise when my brake pads are getting to the replace zone, but I check them pretty frequently so they never get into the danger zone. It's easy to see how much brake pad you have left, except on the rear which is a bit harder, but not impossible.

Grinding noise is a sign that it's time to replace the disks. You can get away with it on cars but there just isn't enough brake disk on the bike to do that. No regrind, just replace.