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Do properly bedded brakes still rust?

B

beardedGTI

Ready to race!
Location
Louisville, KY
Car(s)
2017 GTI Sport 6mt
So with just under 200 miles I took my 2017 sport on the backroads and attempted to bed the brakes in following the instructions of numerous posts and videos. This is the first time I've attempted bedding pads on any vehicle. At about 600 miles I gave her a wash and notice the rotor surface instantly glaze over in a light rust. It's not a blotchy kind of rust that I've seen on other rotors after a wash, but a smooth uniform one. I was under the impression that properly bedded brakes would not rust due to a transfer of brake material to the rotor surface. Is this not the case?

To be clear, my question here is not aesthetics (rust is ugly, why is it happening) but about functionality (did I not bed the pads in correctly?).
 
M

Mk7CarbonSteel

Passed Driver's Ed
Location
Delaware
Slight rust on rotors is normal after getting wet. It happens on all cars. It has nothing to do with bedding the brakes. That may be true for ceramic brake pads, but semi metallics would transfer metal too, that would rust.
 
B

beardedGTI

Ready to race!
Location
Louisville, KY
Car(s)
2017 GTI Sport 6mt
Interesting. So I'm aware that (most) pads have metal content in them. However I've never seen flash rust on a pad itself. I just assumed this was because the composition was way more other stuff than metal. So if there is a thin layer of brake material bedded on my rotor it's a) more metal than anything else b) about to get scraped off when I apply the brakes for the first time.

Is there a sure fire way to tell pads have been properly bedded? I did 10 60-to-5 stops followed by a cool off followed by another 10. Several pieces I read seem to indicate that you'll be left with a semi-gloss grey surface on the rotor face but even after looking at pics of this supposedly bedded surface I found it tough to tell the difference.
 
Finglonga

Finglonga

Drag Racing Champion
Location
Stafford, UK, Earth, Solar System.
I have done 40k miles and my last car had done 70k, they both had rust after getting wet within a hour. Perfectly normal and disappears the first time you use them.
 
B

beardedGTI

Ready to race!
Location
Louisville, KY
Car(s)
2017 GTI Sport 6mt
I totally see now that I could have worded the title of my thread better. To be clear, I'm not concerned about having rust on the rotors. What I am trying to figure out is whether I successfully bedded my brakes. I was using the rust metric simply because my understanding of the bedding process, I thought you would have little to no rust on the surface due to the thin layer of melted composite embedded on the surface. If properly bedded brakes can still rust, what is another metric either testable or observable to tell if bedding was successful?
 
Sandman GTI

Sandman GTI

Drag Race Newbie
Location
Tennessee USA
Finglonga said:
I have done 40k miles and my last car had done 70k, they both had rust after getting wet within a hour. Perfectly normal and disappears the first time you use them.
Click to expand...

Disappears?
I am sure mine ends up on my wheels.
Or that is what it looks like when driven after a car wash.
Hard to keep wheels clean.
 
breaking badly

breaking badly

Banned
Location
St. Olaf
beardedGTI said:
At about 600 miles I gave her a wash and notice the rotor surface instantly glaze over in a light rust.
Click to expand...
Normal.

Brake rotors are made of cast iron and iron WILL rust when wet.

Iron does rust in the presence of water, oxygen and even more
when salt comes into play. You cannot do anything against that
other than keep them dry and/or brake that light rust away.



beardedGTI said:
I was under the impression that properly bedded brakes would not rust due to a transfer of brake material to the rotor surface. Is this not the case?
Click to expand...
Bedding in brake pads doesn't affect rotor rust at all. Nor do
(pseudo) "ceramic" pads help on this.



beardedGTI said:
To be clear, my question here is not aesthetics (rust is ugly, why is it happening) but about functionality (did I not bed the pads in correctly?).
Click to expand...
As mentioned, nothing to do with it.



beardedGTI said:
Is there a sure fire way to tell pads have been properly bedded? I did 10 60-to-5 stops followed by a cool off followed by another 10. Several pieces I read seem to indicate that you'll be left with a semi-gloss grey surface on the rotor face but even after looking at pics of this supposedly bedded surface I found it tough to tell the difference.
Click to expand...
To me, you have completely overdone this. ;) Don't get fooled by
forum talk. Stock brake pads don't require 20 stops. If at all, 6 to
10 would have been enough.
At the latest when they start to smell or begin to fade (do require
more pedal pressure) you're done.
Don't worry, after 20 stops from 60 you are definitely done with it. ;)



beardedGTI said:
To be clear, I'm not concerned about having rust on the rotors. What I am trying to figure out is whether I successfully bedded my brakes. I was using the rust metric simply because my understanding of the bedding process, I thought you would have little to no rust on the surface due to the thin layer of melted composite embedded on the surface. If properly bedded brakes can still rust, what is another metric either testable or observable to tell if bedding was successful?
Click to expand...
Seems to me someone did promise too much. :(

Guess I understood your question from the beginning. It's been
quite clear. :)


.
 
N

nate704

Go Kart Champion
Location
Virginia
please don't forget to wash and wax your rotors after every car wash or rain, so that you can keep the rotors clean and shiny
 
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