If rotors have deep grooves in them are they UNsafe to drive on. Just had my front brake pads replaced and was told that rotors needed to be replaced, but when I pushed them on it, they said it wasn't UNsafe, it just might be noisy. AT what point would driving on these rotors be UNsafe and is there any other reason to replace these front brake rotors sooner than later?
Light scratches and shallow grooves are normal after use and won't affect brake operation.
Deep grooves - over 0.015-inch (0.38mm) deep - require disc removal and refinishing or replacement.
In our state AZ, by law auto shop's and auto repair store's are required to hold rotor's from owner's that are bellow minimum thickness for safety.
It sounds to me that your brake rotor's are not below minimum thickness. Or they would have said flat out replace them. Why they want to replace them and not resurface them, I don't know. But you should alway's resurface or turn your rotor's whenever you replace your brake's. Resufacing the disc brake rotor's produce a smooth, flat surface that will eliminate brake pedal pulsation and other undesirable symptoms related to questionable disc. (Brake noise, uneven pad wear, faster wear on brake pad's.)
Without knowing the thickness of your rotor's I can't say if they need to be replaced. The minimum disc thickness is cast into the hub of your rotor. To check, place a dial indicator at a point about 1/2-inch from outer edge of the disc. Set the indicator to zero and turn disc in place. The indicator reading should not exceed 0.006-inch. If it does the disc should be resurfaced. Or you can take your rotor's to a local parts store like AutoZone and they will do it for you.
Rotor's that are below minimum thickness are unsafe, and should be replaced.
March, 8, 2008 AT 8:17 AM
Grooves decrease the contact surface area between the pads and the rotor. As a result, the stopping power is reduced. It may be unsafe if you have an aggressive drive style or are in a tight situation.