Chirping Mustang

I own a 98 Mustang convertible w/ 84000 miles on the clock. It’s a great car and quite reliable. Lately it has developed a rhythmic chirping sound in the right rear wheel which increases in frequency as speed increases. At first I thought it was suspension-related, but the chirp stops when I apply the brakes, which leads me to believe it’s related to brakes, not springs. Ideas?

Possibly a brake pad wear indicator announcing the brakes need an inspection and service.

A rhythmic chirping sound that goes away when the brakes are applied is the classic sign of a brake wear indicator telling you to replace the brake pads. Have the pads on all 4 wheels checked before you wind up destroying a rotor or two.