, but how do you change the sensitivity of the brakes?

Change pads. Some are more aggressive than others. Go to your local auto palace/ NAPA store and ask for some less aggressive pads (usually organic instead of semi-metallic). You might have picked up a rock that embedded in you pad, making the screech. They must be disassembled (pads off) to check. Do it yourself, it's not too hard. Remove wheel, remove caliper bolts, lift calipers off, inspect. Lube the caliper slides, replace pads, press brake cylinder in, install new pads, reinstall caliper pins & wheel. Talk to the counter guy at the local auto parts place when they're not busy and they can probably help you out.

'Luck.

-Zeke