In general, drum brake squeal is excited by friction induced vibration at the drum-shoe interface. The instability of the vibration depends on various parameter especially friction coefficient. This paper shows the development of minimal model of a drum brake squeal under binary flutter instability which is caused by the velocity independent friction coefficient. The vibration of the brake shoes is considered as the primary unstable component which contributed to the drum brake system squeal. Experimental work is carried out to indentify the value of parameters of this model and also verified the critical value of unstable vibration for squeal. The binary flutter instability occurs when two initially separated and different natural frequencies of the system coupled at a common frequency to produce one unstable mode. The coupling of the modes in this model is between the first torsion mode and the second torsion mode of the leading brake shoe. The effect of the friction coefficient, damping coefficient and the location of centre of contact pressure are investigated.