There are sandpaper scratches on brake rotors.?

Update:

I recently changed the brake pads for my car, even though sometimes when braking they make some squealing sound. I took my car to the shop where I got my brake pads changed and they told me they could sand both the pads and the rotors. Which they did. However, the rotor has visible scratches from the sandpaper used. I want to know if these will fade away, if I need to take my rotors to resurface or if I need to change the rotors.

12 Answers

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  • 12 months ago

    thats what it is

  • zipper
    Lv 6
    12 months ago

    The sand paper marks hurt nothing, and can improve stopping a little bit, they will wear out in short order any way. look for something real to ask about! I always sand my rotors when I replace the shoes, it only makes sense to do it!

  • 12 months ago

    New rotors have been honed so the pads bed in evenly.

  • Anonymous
    12 months ago

    First, I never read your story.

    I will clarify process.

    Resurfacing is putting the rotor in a lathe and a fine layer of metal is cut off which takes off the MIRROR finish. It also cuts off any warps in the rotor so it is perfectly flat. The rotor is STEEL. Only a carbide tip on a lathe can cut steel.(so not sandpaper) Sandpaper won't touch steel.

    . The brake pad(or shoe for drum brakes) is made out of a softer material than STEEL & the fastest way to get it so that there is 100% pad contact with the rotor is have the rough rotor sand off a bit of pad in case one edge of the pad is thicker than the other so it does not land on flat 100% in contact with the rotor surface. So by the rotor sanding off the high points on the pad it achieves 100% contact sooner. 100% contact means fully grabbing the rotor when you step on the brakes.= faster stopping time.

    . You CAN change pads without resurfacing the rotor, but if the pad is tilted a bit, on a smooth rotor it will be like that for a long time as part of the pad touches & part does not contact the rotor at all.

    Do a visual using the palms of your hands. Slap the two flat palms together. That is 100% contact. The left hand is the rotor and the right hand a single pad. Separate the hands again and this time tilt the right hand so it leans on an angle. Now bring the hands together and stop as soon as they touch and you will see that either the tips of the fingers touch the rotor or the heel of the right hand touches the left hand but the rest is not touching. What part is not touching IS NOT BRAKING. It is not 100% contact. so the brakes are not as solid. for stopping that rotor from turning. Having the roughed up rotor allows it to grind away at the high points faster to give you good brakes sooner.

    . The squealing you heard was the brake pads near the end. The squeal lets you know because you can't see it that the pads are almost gone.

    . You do not want to get to the point of no more pad because steel on steel does not stop you(and the backing surface to the pad is steel. It will damage the rotor as it gouges out the rotor.

    By the time you need pads again, the surface will be a mirror surface on the rotor. They have to resurface again for the new pads just so the pads seat well.

    **Check on You tube to see them resurface a rotor. It is automated because it is a boring job. Both surfaces are done.

    If it is still squealing then they put anti squeal tabs or anti squeal compound on the back of the pads and that should fix it. Tell at them if it is still squealing. They know how to fix. That should be part of the cost of doing the brakes.

    Some cars don't need the anti squeal compound or metal tabs.

    Auto mech 35+ yrs.

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  • M.
    Lv 7
    12 months ago

    Your question is about abrasive scratches, but your complaint is about squealing noise.

    Noises often come from places other than the surfaces of rotors and new friction pads.

    The surface, runout, thickness differences around the rotor dictate reusing the rotors as-is or machining or replacing the rotors.

    I'm wondering what they used to sand the rotors. 40 grit sandpaper?

    I'm curious if the squealing ceased.

    -General automotive mechanic since 1972

  • Anonymous
    12 months ago

    Sanding pads and rotors is never necessary but will do no harm at all. The pads contain a minute amount of abrasive which keeps the the rotors pristine each time you apply the brakes. Brake pad squeal is due to high frequency vibration when the brakes are lightly applied. A smear of copper based grease on the back of the pads cures this.Your monkey mechanics are unaware of this of course. Don't go there again.

  • John
    Lv 7
    12 months ago

    Gotta be. It helps them break in.

  • 12 months ago

    If they're not deep then I wouldn't worry about it. If you feel like you need to spend the money you can get them "turned"...(basically sanded down by a mechanic).

  • Bill
    Lv 7
    12 months ago

    Somebody used sandpaper on the rotors, or you let the pads wear down to the metal.

  • 12 months ago

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