2

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.

Fattie
  • 371
  • 1
  • 13
  • 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 Jan 20 '23 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 Jan 20 '23 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 Jan 20 '23 at 16:42
  • they do in fact need to be replaced! so it works out fine... TY ! – Fattie Jan 20 '23 at 16:55
  • Fair enough. Difficult to tell from the photo. – jwh20 Jan 20 '23 at 17:38
  • @jwh20 Whatever rust is on the rotor hat, the unprotected rotor contact surfaces have rusted far more. The coating is merely for cosmetic purposes, they only painted these because the vehicle is expected to have fancy wheels with small spokes. See other vehicles, particularly trucks, that use unpainted rotors where surface corrosion is very normal. – user71659 Jan 20 '23 at 19:31
  • @jwh20 just TBC, I meant "from driving it and using the brakes, I am anyway going to replace the rotors and pads ..." – Fattie Jan 20 '23 at 19:33
  • @user71659 ah, thanks for pointing out that bit is called a "Hat", good one. In fact ... – Fattie Jan 20 '23 at 19:34
  • @user71659 yes TBC, the rust on the "hats" on both sides looks unappealing (the car looks as-new otherwise) so it's worth it to me to replace them for that (cosmetic only) reason. I understand on the disks, surface corrosion is normal! however, setting aside the cosmetics, the car has slightly weak brakes (softish long pedal travel, somewhat erratic behavior). for this reason I am bleeding/new fluids (good idea anyway on a 10 yr old) and changing the rear rotors/pads will "eliminate that from the equation" I'm sure you get what i mean. – Fattie Jan 20 '23 at 19:37
  • (aside, there's talk that it might be the "pins" on the calipers so maybe they all have to be replaced too! in terms of the soft brake mystery) – Fattie Jan 20 '23 at 19:43
  • BTW it was indeed the "pins" ! I simply completely replaced all the calipers, and, I got lovely brembo dissks (which obviously includes the "hat" which is now shiny as new Italian steel!) – Fattie May 19 '23 at 11:25

1 Answers1

3

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

Bob Cross
  • 24,365
  • 11
  • 83
  • 164
jwh20
  • 12,092
  • 1
  • 15
  • 25
  • Totally understood now - THANKS! :) perfect answer – Fattie Jan 20 '23 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. – Pᴀᴜʟsᴛᴇʀ2 Jan 20 '23 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 Jan 20 '23 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. – Pᴀᴜʟsᴛᴇʀ2 Jan 20 '23 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 Jan 20 '23 at 21:57
  • @user71659 - Well, believe what you want to believe. I'm not talking about a "rim standoff". I'm talking about the back side of the rim which faces up against the hat of the rotor. The hat isn't 5" tall. In fact, the rotor is only ~2.65" from back side of the rotor to the top of the hat ... because I did look it up. Anyways, we'll have to agree to disagree. – Pᴀᴜʟsᴛᴇʀ2 Jan 20 '23 at 22:06
  • @Pᴀᴜʟsᴛᴇʀ2 This video shows the entire rotor. It is clear that it's one piece. Another example of the wheel being removed without a spacer. – user71659 Jan 20 '23 at 22:19
  • @user71659 - Why do you keep talking about a spacer? Who's talking about a spacer? I'm talking about the backside of the rim. You know, the mounting boss which actually mounts to the front side of the rotor? And in the 2nd video, you can see the rim, it's OBVIOUSLY not the same kind of rim so it's not going to look the same. If you'd like to continue your side of this semi-quasi disagreement, please post it in the Pitstop as comments are not meant for drawn out conversations. – Pᴀᴜʟsᴛᴇʀ2 Jan 20 '23 at 22:27
  • hi @Pᴀᴜʟsᴛᴇʀ2 FYI I can absolutely assure you that in this case (on the lexus IS350C) it turns out it is definitely ONE PIECE. I bought a new pair of rotors (brembo) and on both the factory rotors (my photo at the top of the page) and the brembo rotors, the hat-section is definitely all the same piece as the rotor section. the hat is on the exterior, facing away from the car (as in my photo at the top) – Fattie Feb 27 '23 at 18:08
  • actually here is the exact part showing the large hat (which is all one piece) https://www.brembostoreusa.com/product/09c93011-brembo-rear-left-or-right-brembo-uv-coat-vented-brake-disc-rotor-for-lexus-gs350-rc350 – Fattie Feb 27 '23 at 18:11
  • @Fattie - Either I'm not explaining myself well, or you just aren't getting it. I wasn't suggesting the your rotor is more than one piece. Regardless of whether the rotor is mulit-piece or a single one, the part which stands out in the middle from the machined surface which attaches to the hub is called the "hat". The actual part which I was talking about and had rust on it appears to be the back side of the rim. There is a line between the two in the image. – Pᴀᴜʟsᴛᴇʀ2 Feb 27 '23 at 18:50
  • @Pᴀᴜʟsᴛᴇʀ2 gotchya yeah I meant to type "unless I misunderstand you guys" ! :) – Fattie Feb 27 '23 at 19:50