Those are the servos that came with the DX3 radio system. I got rid of those servos 1st thing for 1/5 scale use. You need a much higher torque servo for the brake system.
Here is yours:
Z590M High Torque Servo
Specs
Size Category: Standard
Type: Analog
Application: Surface, Steering car and truck
Torque: 70 oz-in @ 4.8V, 85 oz-in @ 6V
Speed: .18 sec/60° @ 4.8V, .15 sec/60° @ 6V
Length: 1.55 in
Width: 0.73 in
Height: 1.46 in
Weight: 1.6 oz
Motor Type: 3-pole ferrite
Gear Type: Metal
Price: $40.00
I use this one:
DS8711 Ultra Torque Servo
Specs
Size Category: Standard
Type: Digital
Application: Ultra torque (Aircraft Use Only)
Torque: 347 oz-in @ 4.8V, 403 oz-in @ 6V
Speed: .19 sec/60° @ 4.8V, .15 sec/60° @ 6V
Length: 1.58 in
Width: 0.82 in
Height: 1.56 in
Weight: 2.36 oz
Bushing Or Bearing: Bearing
Gear Type: Metal
Gear Material: Metal Alloy
Price: $140.00
That is your main issue...
