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Strange Brake Problem

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After my last DE event I washed my car. There was a lot of brake dust on the wheels and so I used a strong jet of water to wash most of it off. Some of the spray inadvertently went onto the rotors and actually managed to wash out the brake dust through the cross drilled holes. Needless to say, the disc started rusting almost immediately. So far, this is all normal. I went for a drive afterwards and braking was significantly less effective. I figured the pads must still be wet, and the problem will go away after a couple of stops. It did not, even after 2 more days of (careful) driving. It felt like the brakes were slippery and I needed a lot more pressure to stop. First I suspected air in the lines, but pressure bleeding did not help.

I bit the bullet and removed all pads. What I found was uneven wear on all pads. Parts of the pads were smooth (which is how I would expect them to look) but other portions were rusty looking or rough (see middle of pad in the picture). The rough parts on the pad typically corresponded to still rusty looking tracks on the rotors (see middle of the rotor, towards the left of the picture). All the rotors are scored, but they have been this way for a while. They seem to be within the wear limit.

Question for the collective intellect:

1) Is it normal for rotors to look this scored?

2) What's the mechanism behind this strange problem? Moist brake dust in the cross drilled holes contaminated the pads which in turn transferred to the discs?

3) Anyone else have had this happen, and what was you remedy?




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Looks to me like your pads/rotors are glazed. It also looks like some of the pad material got so hot it created patches of buildup as it broke loose.

I think you need new pads and rotors. You might also consider some track pads and change them before and after each event.

Here is a good article on what happened...


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You have corroded discs (that may have also been overheated). The 'rings' around the disc am i right in assuming they are 'rust' rings?? I had this on the innner face of me rear discs, which tends to originate from getting your discs wet, letting them rust up and not drying them off quickly enough or hard enough..... My pads (and discs) when i took them off looked exactly like yours. Fortunately the rust was only on the inner face of the rears, so didnt really affect my braking too much. These brakes are designed for 'fast' driving use and need to be 'stood' on frequently in my opinion to clean off any c**p that gets on there (and rust).

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You have corroded discs (that may have also been overheated). The 'rings' around the disc am i right in assuming they are 'rust' rings??

Yes, they are rust rings.

I agree with you all, that probably the best remedy is to get new pads and rotors. While waiting for my mail order I decided to take all the pads out, and grind them flat with my sander. Next I cleaned the rotors and pads with brake cleaner, and reseated the pads. Braking has improved markedly and because the pads started of flat, the height of the ridges in the rotors. has been reduced somewhat. The rust rings are also gone.

Not sure I would recommend doing this, but at least it did improve the situation.

I am also amazed how easy it is to replace the pads on these cars. You can just about do it with out any tools.

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I am fairly sure they can 'skim' these discs on the car. Went in to the dealer one day and saw a 911 on the stand with the 'skimming' machine hooked up, it had cross drilled discs (think it was a C4S). I have also been told (when i had the same issue) that i could have mine skimmed. This was by two different places......... I didnt, so i'm not 100% if its possible but they did know what discs i had so i'm a good 98%. In any case like we have all said, ideally new or 'skimmed' discs with new pads. The cheap (and nasty) option is new or flat pads with your old dics (which you have done) to wear that rust off (a bit), with even less braking efficiency for a while!! Careful! :unsure:

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