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Rust - rear dics

Discussion in 'New A3/S3 (8V Chassis)' started by Little Red Monster, Nov 19, 2013.

  1. Little Red Monster

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    Yes, I appreciate it is normal for discs to rust, but although my front discs clear of rust as soon as I go on a short run, the rears do not appear to operate very often. Following a 6 mile drive and braking a number of times, the rear discs were still rusty with very few signs of it being removed. It would appear all the braking is concentrated on the front brakes, with very little if anything on the rears. I did brake very hard a couple of times, but it has made little difference. I understand long term rust left on a disc can cause issues with braking performance. With my last car, I could drive off with the handbrake gently applied on for a few yards and this would have cleared the problem, not an option with the new A3 and its electronic handbrake? Anyone else notice this? Any solutions?
     
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  3. cemerson

    cemerson Well-Known Member

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    It's not so much that the braking is concentrated there (it is a bit), but the whole weight of the car pushes forwards as you brake and causes the front brakes to do so much more work than the back. The handbrake usually uses all of them.

    I wouldn't worry about braking performance - as you have discovered the backs aren't used anywhere near as much as the fronts in braking so shouldn't matter.

    You can always pull the handbrake switch up and hold it to 'emergency' brake (somewhere quiet!) to see if that helps - can't do 'gentle' though!
     
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  4. JimmyH

    JimmyH Active Member

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    Callipers may be seized.
     
  5. RobH_S3

    RobH_S3 Active Member

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    Don't the brakes automatically massage the disk to keep heat in them so the brakes are predictable in all conditions? The rear brakes should still be working and deffo shouldn't have rust on them after a run. The brakes are front biased but no where near to the extent of the rears rusting up.

    I would be taking it to the dealer to get looked at. You may not notice the rears not working at low speed but at high speed you will need them to keep the car neutral and stability control uses the brakes to maintain control aswell.
     
    #4 RobH_S3, Nov 19, 2013
    Last edited: Nov 19, 2013
  6. smudger69

    smudger69 Member

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    Mine are exactly the same and I had it at two dealers and Audi UK were involved too. All in all I was told its normal and nothing they can do to sort it. So it was a waste of time going to the dealers with the problem. I sent pictures to Audi UK so their technical department could look at them and they also said it was normal.
     
  7. Silky-S3

    Silky-S3 Is loving his new 8V S3!

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    Are you guys talking about the face of the disc or the hub?
     
  8. smudger69

    smudger69 Member

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    On mine it's the face of the disc about three quarter inch all the way round.
     
  9. dieseldoug

    dieseldoug Member

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    After I wash the car the docs show the colour of orange on them all, take it along the road for 1/2 mile round trip and all docs back to normal whith no hard breaking very light breaking in fact.
    As mentioned above you may have sticking slides on your callipers.
     
  10. steeve

    steeve Well-Known Member

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    There is a similar problem on Subaru STi's the Brembo's are stunning brakes but the rears tend to get a little rusty. It's used as a sign that the car hasnt been driven all that hard. To clean them on my STi you had to brake hard a few times, and I mean hard, like your life depended on it. Or like a Subaru should be driven.
    Try it and let me know.
     
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  11. cuke2u

    cuke2u Well-Known Member

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    Braking force on a car is usually 70% front and 30% rear. The only time I've noticed rust on my rear brakes is after I've cleaned the car or it has been raining, the rest of the time they are clean...
     
  12. JimmyH

    JimmyH Active Member

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    brake bias all depends on the drive wheels, engine size, amd disc size! Some are 90/10 down to 60/40.
     
  13. cuke2u

    cuke2u Well-Known Member

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    And if it is wet, that's why I said usually...:o.k:
     
  14. slipped_disc

    slipped_disc Member

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    Just had my A3 in with Audi today for a faulty fuel flap release, and mentioned that my offside rear disc was 50% rusty (all the others are fine). I was expecting them to say, "Don't worry - that's normal.", but instead they said they'd heard reports of this. They took photos and were going to send them to Audi HQ. They said they'd plan to change the disc and pads at the car's first service next month.

    Has anyone else had this problem, with a similar response from Audi?
     
  15. ChiYoung

    ChiYoung Active Member

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    Try going reverse and braking, makes the car apply more pressure on the rear brakes. As we some people know from the chewaca noise on first meters.
     

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