What actually is this?

TBC the two arrows are pointing to the same thing; the left arrow is pointing to the circular part of the Thing and the right arrow is pointing to the side part of the Thing.

Is it actually just part of the disk? Is it separate? Can it be replaced on it's own?

Is it easy enough to replace, or, is it more like fooling with the axle??

On my (previously mentioned :) ) lexus IS 350 C, this is the rear wheels.

It's the only thing that isn't factory-new on this low-mileage 2012 so it seems a shame!

enter image description here

(*) FTR the brakes seem a touch soft (suspiciously long pedal travel) so as well as having the fluid bled/replaced, it may be advisable anyway to replace the pins? calipers? etc. If so could do it all at once.

  • BTW - It's a bit odd for the rotor to rust like that. In most cases that part is coated with a protecting coating to prevent rust. Is it possible this was a flood vehicle?
    – jwh20
    Commented Jan 20, 2023 at 16:10
  • great point @jwh20 - you know, it wasn't a flood vehicle, but, it has very low mileage. and it is 10 yrs old. and it lived in Fla. so a bit humid? to me it does not appear to be coated. maybe just from sitting around disuse? maybe it was replaced with a cheap oem part ? IDK ...
    – Fattie
    Commented Jan 20, 2023 at 16:17
  • That's possible. The air in FL, especially near the coasts, can be very salty and that can contribute. It looks to be cosmetic so unless it's bothering you there is no need to replace it now. Eventually the rotors will need replacement due to wear and you can get new ones that don't have rust then.
    – jwh20
    Commented Jan 20, 2023 at 16:42
  • they do in fact need to be replaced! so it works out fine... TY !
    – Fattie
    Commented Jan 20, 2023 at 16:55
  • Fair enough. Difficult to tell from the photo.
    – jwh20
    Commented Jan 20, 2023 at 17:38

1 Answer 1


The part you are highlighting is the BRAKE ROTOR. Yes, it can be replaced on its own and should be if it's worn or damaged.

You're pointing to this part of it but it's all one piece:

Brake Rotor

Here's the one for the car in question, showing the large hat (Brembo 09.C930.11)

enter image description here

  • Totally understood now - THANKS! :) perfect answer
    – Fattie
    Commented Jan 20, 2023 at 16:08
  • The big thing you've totally got wrong in your answer is: the rust isn't on the rotor - it's on the rim. And that's not all one piece. There is a break between the rim and the rotor. I mean, the rust is probably 95+% on the rim and less than 5% on the rotor. Commented Jan 20, 2023 at 18:39
  • @Pᴀᴜʟsᴛᴇʀ2 No, you're wrong. It's not a "rim" it's a "rotor hat". Only in custom racing applications is the hat separate from the rotor--all braking forces are transmitted through the hat into the wheel thus a single piece design is more durable. The manufacturer here has painted the rotor hat largely for appearance as rust isn't being scraped away by braking action.
    – user71659
    Commented Jan 20, 2023 at 19:19
  • @user71659 - Look again. Yes, there's a hat which is attached to the rotor (one piece). Then there's the standoff which is the back of the rim. They separate where the line is which goes all the way around. It is about 1/2 and 1/2 hat and rim standoff. Yes, the rotor/hat is a "single piece design". I know what a hat is. I know it is contiguous with the rotor itself (in this case). I also know the other part is the rim. Commented Jan 20, 2023 at 21:18
  • @Pᴀᴜʟsᴛᴇʀ2 No it's not. The rust is completely on the rotor hat. Look up the actual part at an auto parts site, there is no "rim standoff". What you're confusing as a separate piece is a groove cut between the top brake disc and the hat, a similar groove is in the picture above. This is to prevent the top surface from warping due to thermal expansion against the hat.
    – user71659
    Commented Jan 20, 2023 at 21:57

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