Whenever you can see or feel grooves in them.
Yes. It does not make a difference whether is is the conventional, slotted or drilled rotors. They can all be machined in a brake lathe with the same accurate result.
Your front brake rotors need to be machined or replaced.
The Sintra has rear brake pads and disks. Inside the disks brakes are shoes for the hand brake. So yes, is does have rear shoes, but only for the handbrake.
you have out of round brake rotors, they can be replaced or machined if they are thick enough, the front pads should be replaced or placed on sand paper on a flat suface to remove the glazing so they will seat properly to freshly machined surface
worn pads change your brake pads and get your rotors machined while your at it
You need the front rotors machined or replaced.
Disks on the front, drums on the rear of my 1996. Disks all around on the 2002.
the brake rotars are out of round or warped.have them machined
Take them off and measure the machined surface for width and the diameter.
Brake vibration is usually caused by the brake rotors being warped. The rotors must be machined or replaced to correct the problem. if you can feel it in the steering then the drums are or rear rotor could be warped
Brake rotors or drums need to be machined or replaced. If it causes steering wheel shaking, check front brakes. If happens when applying parking brake look to rear brake problem.
No, by the time your breaks are making a bad noise, they will have damaged the disks.