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I have a 2007 Audi TT 2.0 TFSI that has been sat for a while and the discs are all rusty and need replacing. I ordered some new discs from the internet and entered the registration number of my car to find ones that would fit. The new ones have just arrived and while they are the same diameter as the old ones they are not as thick. The old ones are vented whereas the new ones are solid so the old vented ones are considerably thicker than these new solid ones. Is that ok? Can you fit thinner discs or do you have to match the thickness of the previous discs?

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    Rust is not a problem on discs. Apply the brakes a few times and it will be gone. Discs will get a rust "bloom" ( very thin layer) overnight under some conditions of humidity ,etc. – blacksmith37 Apr 14 '20 at 14:40
  • I agree with @blacksmith37 on this, you only need to replace the discs if they are worn out of tolerance or warped. Sitting won't cause these issues, the chances are good your discs are fine. There will be plenty of other things you can spend your money on. – GdD Apr 14 '20 at 20:55
  • Oh no its ok they are quite old and worn and its not just the faces of the discs that are rusty all the edges are very rusted and bubbled to the point where bits are flaking off. I'm turning it into a track car so I was upgrading the brakes anyway. – geoffs3310 Apr 15 '20 at 11:22
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You have ordered the incorrect discs, or the supplier has made an error.

You will need the correct vented, thicker, disc as the caliper has a « jaw » sufficiently large for the combined thickness of pads and vented disc.

If you do try to use the solid disc then the pistons could easily pop out of the caliper and you have zero brakes...

Contact the supplier and get the correct vented disc.

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    That's not the only problem. Solid discs can't get rid of the heat so well, so heavy braking at speed will at least cause more serious brake fade, and at worst could cause the disc to deform or break with serious consequences. – Graham Apr 14 '20 at 18:55
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    @Graham Brake fade is irrelevant if the calipers don't fit the disc. As for OP, there's no way the VIN can tell you what brakes go into the car, so it's not the supplier's fault. Only a VW dealer can cross-reference the BOM from the VIN to find the brakes that went into that specific vehicle. Either that or OP can take the part number from the existing brakes. These vehicles can come with a few different types of rotors from the factory, depending on what was ordered when it was purchased, iirc. – J... Apr 14 '20 at 19:13
  • @J... My friend owns a workshop and his supplier can very well get you the right brakes by vin. I suppose VW would get anti-trust issues in the EU if they dint provide this data to aftermarket parts re sellers. Do you really think any reseller would offer to search parts by vin, if that they would not able to deliver meaningful results? (Some french cars still give you headaches though as they have different brake parts sometimes only depending on production month of the same car) – Daniel Apr 14 '20 at 21:41
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    @Daniel Maybe it's different in the EU. Just picked a shop at random in NA and they say : Only an authorized Audi VW dealer can access the bill of material info, which reveals what braking components that were used to build your car and the subsequent brake code. Blauparts is an independent Audi VW parts specialist and doesn't have access to this bill of material info. We therefore cannot tell you what your brake code is. – J... Apr 14 '20 at 21:52
  • @J... In the EU we also have type and model number in your papers, which gets you to your part 90% of the time. Rest 10% you have to look at the old part to see which is which. Just piked a random shop and by make model year and motor I got this PS: They also show the original parts numbers for Audi that could be 1K0 615 301 AA or 5C0 615 301 B or 5Q0 615 301 F which all fit this rotor. – Daniel Apr 14 '20 at 22:01

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