Brake Disc Skimming: When Can Discs Be Skimmed and When Should They Be Replaced?
When brake discs become worn, scored or develop an uneven braking surface, replacing them isn't always the only option.
In the right circumstances, brake disc skimming can restore the braking surface and allow a serviceable disc to continue doing its job safely.
But not every brake disc should be skimmed.
The important question isn't simply “Can we skim it?” It's whether the disc will still meet the required specifications once the machining is complete.
What is brake disc skimming?
Brake disc skimming is a precision machining process that removes a small amount of material from the braking surfaces of the disc.
The aim is to create a smooth, even surface for the brake pads to work against.
At The Cape Brake Company, we perform both onboard and off-car brake disc skimming using dedicated and specialist workshop equipment.
Why would a brake disc need skimming?
Over time, the working surface of a brake disc can change through normal use.
Depending on its condition, skimming may be considered where there is:
- Surface scoring or grooving
- Uneven wear
- Surface irregularity
- Brake vibration associated with the disc surface
- A need to restore an appropriate mating surface for new brake pads
However, the presence of one of these conditions does not automatically mean the disc can or should be skimmed.
It needs to be inspected and measured first.
How do we decide whether a disc can be skimmed?
Brake discs have dimensional limits.
Before machining, the condition and thickness of the disc need to be assessed to determine whether sufficient material remains for it to be machined while still staying within the applicable specification.
We also look at the overall condition of the component.
If the disc is unsuitable for safe continued use, machining it simply to avoid replacement would not be the right repair.
When should a brake disc be replaced instead?
There are circumstances where replacement is the appropriate option.
These can include a disc that is:
- At or too close to its minimum allowable thickness
- Excessively worn or damaged
- Cracked
- Severely scored or deteriorated
- Unsuitable for machining
- Unable to remain within specification after the required material is removed
In those cases, CBC will recommend replacement rather than trying to save a component that should no longer be used.
Is skimming always cheaper than replacing brake discs?
Not necessarily, and price shouldn't be the only factor in deciding which route to take.
The cost and availability of replacement discs vary enormously between vehicles. On some vehicles, replacement may make more sense. On others, a serviceable disc with sufficient material remaining may be a good candidate for machining.
Our approach is to assess the component in front of us and recommend the option that makes sense for the vehicle.
Should brake discs be skimmed when fitting new brake pads?
Not automatically.
If the existing disc surface is in good condition and the disc remains within specification, machining may not be required.
Where the surface condition does need attention, skimming may provide the new brake pads with a clean, even mating surface, provided the disc is suitable for machining.
Again, the decision should come from inspection and measurement rather than a blanket rule that every pad replacement requires either new or skimmed discs.
What is the difference between on-car and off-car brake disc skimming?
With on-car skimming, the brake disc remains fitted to the vehicle while it is machined using equipment attached to the vehicle.
With off-car skimming, the brake disc is removed and mounted on dedicated machining equipment.
CBC currently prefers off-car brake disc skimming, which allows us to work with the component directly and assess it as part of the process.
Does CBC only skim brake discs?
No.
Our workshop machining services also include brake drum skimming and flywheel skimming where the component is suitable for machining.
For brake drums, the same basic principle applies: the component must be inspected and remain within its allowable specifications.
Flywheel skimming is a different application but uses precision machining to restore the mating surface where appropriate before clutch installation.
Skim or replace? Measure first.
There isn't a responsible one-size-fits-all answer.
A brake disc shouldn't be replaced simply because skimming exists, and it shouldn't be skimmed simply because machining is possible.
At CBC, we prefer to inspect, measure and then recommend.
If the component can be safely machined and doing so makes sense, we'll tell you. If replacement is the correct option, we'll tell you that too.
Need your brake discs checked?
If you're experiencing brake vibration, scoring, unusual brake noise or you're replacing brake pads and aren't sure about the condition of your discs, we can inspect them and advise whether they can remain in service, be skimmed or should be replaced.
The Cape Brake Company
207B Main Road, Strand
WhatsApp: 067 194 7039
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