Brake Systems: Rotors
NOTE:
Determine the need to recondition based upon individual rotor conditions that follow. Friction material replacement does not require rotor reconditioning unless other justifications exist. Do not recondition new rotors unless it does not meet installed OEM specifications. It is not necessary to replace rotors in axle sets unless required by the vehicle manufacturer. However, when replacing or reconditioning a rotor due to the conditions that follow, you may suggest reconditioning of the other rotor on the same axle to eliminate uneven braking behavior. Determine the need to replace based upon the individual rotor conditions that follow. Reconditioning is defined as machining and block sanding, or block sanding only. Block sanding is defined as using 120-150 grit sandpaper with moderate to heavy force for 60 seconds per side. Always wash rotors after servicing or before installing.
| Condition | Code | Procedure |
|---|---|---|
| Corrosion affecting structural integrity | A | Require replacement |
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NOTE:
Examples of severe corrosion are: composite plate separated from friction surfaces and cooling fins cracked or missing.
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| Cracked | B | Require replacement |
| Hard spots | 2 | Suggest reconditioning or replacement of rotor according to OEM specifications |
| Lateral runout (wobble) exceeds OEM specifications | B | Require re-indexing, reconditioning, or replacement according to specifications |
| Measured thickness is less than OEM discard specifications | B | Require replacement |
| Rotor thickness is less than OEM ""machine to"" specifications but thicker than ""discard at"" | 1 | Suggest replacement |
| specifications, and rotor does not require reconditioning | ||
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NOTE:
Only applies to vehicles for which OEM ""machine to"" specifications exist. If OEM does not supply ""machine to"" specifications, the rotor may be worn to discard specifications.
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| Rotor thickness will be less than OEM ""machine to"" specifications after required reconditioning | B | Require replacement |
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NOTE:
If OEM does not supply ""machine to"" specifications, you may machine to discard specifications.
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| Surface finish incorrect | B | Require recondition or replacement |
| Surface is rust-pitted | B | Require reconditioning or replacement of rotor according to OEM specifications |
| Surface is scored | B | Require reconditioning or replacement of rotor according to OEM specifications |
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NOTE:
Scoring is defined as grooves or ridges in the friction contact surface. Some vehicle manufacturers require machining when scoring exceeds their allowable specifications.
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| Tapered affecting performance | A | Require reconditioning or replacement |
| Thickness variation (parallelism) exceeds OEM specifications | B | Require reconditioning or replacement of rotor according to OEM specifications |