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My father's Opel Astra F 2008 has thick bands of rust on the rear brake rotors. Both brake rotors are almost identical. Is it possible that the pads only cover the non-rusted part of the disk, or is this always indicative of a braking issue?

Bands of rust

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The inside band is not an issue. There is space between where the brake rides on the rotor (the shiny part) and the hat (the hub area). There has to be space here to allow the rotor to rotate independently of the brake pad and caliper.

The outside band may be more problematic. On most disk brake setups I've looked at, there will be a small band, usually measured in millimeters between the shiny part and the outside of the rotor. I cannot tell the exact measurement on yours, but it seems to be much broader than what I'm used to.

Two things to look for here to tell if you have a potential issue. First, look at the shiny area on the back side of the rotor. This area should mirror the same area you are seeing on the side we are looking at. Secondly, look at the disk opposite this one on the same axle. Does it look the same? If the rotors look the same on each side and on both sides of the axle, then there is probably not much to worry about. If, on the other hand, there are discrepancies, then there is probably a need to have them looked at. It could be a chunk of friction material has come lose and therefore there's not as large of an area of contact being made to the rotor. This causes uneven braking, which may cause other issues down the road.

  • Thanks for the detailed answer. The other side on the same axle looks similar, the top region of rust might be slightly thinner (but the same height). It's late here now, tomorrow I'll try to get a mirror between the disk and the dust shield to inspect the inner side of the rotor. – Ives Mar 5 '17 at 21:29
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    @Ives - It is hard to differentiate between the dust shield and the edge of the rotor. Upon closer inspection of the image you posted, it looks as though the actual "band" at the top is not as great as I thought. Really, I don't think you have much to worry about. The contact area of the rotor looks in really good shape without a lot of ridges. If the back side looks about the same, I think it's looking good. Also, double check to ensure you have enough meat left on your brake pads while you're there ... might as well check for piece of mind. – Pᴀᴜʟsᴛᴇʀ2 Mar 5 '17 at 22:48
  • I was unable to visually inspect the inner side of the rotor due to the close proximity of the dust shield. I did however perform a "digital" evaluation in the true sense (using my digits), and it feels like the lip on the inner side is just as wide as the one on the outer side. So I guess the pads just cover a relatively small area by design. The pad has approximately 3 to 4 mm of material left (visually). Thank god for open rims, this would be 10x more difficult through steel rims like the ones on my car. – Ives Mar 6 '17 at 18:47
  • Just to clarify: if the shiny part has/had lots of rust on it, is that a problem / is that indicative of a problem that needs to be fixed? – ashes999 Jun 17 '17 at 20:50
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If the size of the pad matches the "clean" surface then no, you don't have an issue - until, that is, you try to remove the pads...

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