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I've seen people commenting about this before but this is the worse case I've ever seen. I wonder if there has been a change in the steel used for the rotor? Has this always been a problem with older models, in particular the C7? I kept my C6 outside and don't remember anything as bad as what this picture shows. It's a new addition with only 200 miles on it.
I also wonder if GM could pony up a better quality, rust resistant rotor based on some type of stainless alloy? Anyone know of a reason why stainless couldn't be used for a rotor.
Assuming this happens when you wash the car? If so right after washing it drive around the block lightly riding the brakes. Thats has been my process on all my corvettes..... then I pull into the drive and dress the tires. Rotors are dry and rust free as are the tires.......... dry.
Yes it does and it lands all over that pretty mega dollar wheel as you can see in the picture! Believe it or not that brownish (I would say rust colored wheel, but I'm not that crude) wheel used to be black....
I never let it happen! As you say the brown iron oxide gets on the wheels! When I had black wheels on my 2014 Z51 it was very noticeable the few times it started to rain and I quickly pulled into the garage! Since my first Vette in 1988 (the C8 will be my 6th) I always drive my car right after washing! All you need to do is get the rotors warm and it won't form.
My MO is right after drying the car I drive it a short distance down the block applying the brakes aggressively a few times. Just like the energy required to accelerate, need the same to stop! It turns into heat!
Then I pull in the driveway I clean the water drops from the mirrors and rear spoiler etc. Then with a rag, clean any water from the wheels and apply tire dressing! Very little extra time!
SIDEBAR
I recall when someone purchased a C7 as their first Vette and after seeing the brown rotors after he washed it said never saw that in any prior cars. I asked if he always had used car washes. He said yep! You always drive the car after going to a car wash!
Aren't those ceramic brakes megabuck brakes? Rust resistant alloys typically cost more than cheaper steel. Just a matter of trying to meet a price point.
From Google: According to several people on the AMG forums, they received a carbon ceramic brake rotor and pad change estimate of somewhere between $15,000 and $18,000 when the time finally came to do the work.
I think that price is for one wheel. For the price of 4 brakes you can buy yourself a new C8!
Last edited by tdrake2020; Jul 16, 2020 at 04:20 PM.
You can’t use stainless because it’s sucks at absorbing and managing large amounts of heat.
Carbon Ceramic Rotors are available but those will cost you $12000 for a brake job. So take your pick.
I figured there had to be a reason other than cost. Seems like some smart chemist/engineer could find a rust resistant material that works. I doubt we'll ever see carbon ceramic rotors on a C8 the near future.
As far as the alloy goes: this is cast iron, not steel. A cast Iron with a low viscosity when molten so it takes on the shape of the mold easily and accurately.
Cast Iron has several properties that make it better than steel, it is (ahem) castable at low cost and high yield, easily machined (if dirty) and resistant to vibrations (noise), fairly strong and finally, it can take a lot of heat. And BTW mild steel rusts faster than CI. Cast Iron tends to rust on its surface, with little pitting (unlike mild steel).
The surface rust goes away as soon as the brakes are applied.
Carbon ceramic brakes are hideously expensive
Carbon Carbon brakes are cooked in an autoclave in an ammonia atmosphere for 6 months (MONTHs) to have the carbon permeate the carbon mesh--this is not related to carbon fiber at all. If you think Carbon Ceramic brakes are hideously expensive, these are in another league altogether.
Great post! I'm not a metallurgist, but don't different quality cast iron alloys exist? i.e. One alloy that rusts before your eyes and another that rusts slower?
Great post! I'm not a metallurgist, but don't different quality cast iron alloys exist? i.e. One alloy that rusts before your eyes and another that rusts slower?
Rotor iron also has specific alloys to improve the heat characteristics as well. Lots of carbon and usually some chrome and Ti to improve friction. While not exactly high tech - it is engineered.
If the pads are bedded well they leave a layer on the rotor (that is how they work best in fact) and it won't rust as quickly.
Great post! I'm not a metallurgist, but don't different quality cast iron alloys exist? i.e. One alloy that rusts before your eyes and another that rusts slower?
Originally Posted by KNSBrakes
Rotor iron also has specific alloys to improve the heat characteristics as well. Lots of carbon and usually some chrome and Ti to improve friction. While not exactly high tech - it is engineered.
If the pads are bedded well they leave a layer on the rotor (that is how they work best in fact) and it won't rust as quickly.
-Ken
Agree, won’t rust "as quickly" BUT they will rust. Just washed my 2017 Grand Sport with well bedded pads/rotors this morning and they were brown within 1/2 hour.
However just like the 5 Vette’s since my first in 1988, drove it down the block a few hundred yards applying the brakes hard and all gone. Suggest poster do that after washing! It’s not GM being cheap. There are some coatings surface treatments used but typically not on performance rotors! Stopping is key design issue for a Corvette!
As I mentioned - after pulling back in the driveway picked up the inevitable water drops that came from inside the mirrors and rear spoiler. Applied tire dressing and used a rag to pick any water etc on the wheels! Note it doesn't happen after driving in the rain because even modest braking has to dissipate a lot of energy, all converted to heating the rotors!
Great post! I'm not a metallurgist, but don't different quality cast iron alloys exist? i.e. One alloy that rusts before your eyes and another that rusts slower?
There are at least 4 different kinds of cast Irons, and dozens of flavors within each kind; some of which are created by temperature×time×diffusion after being cast,..... this is a science in an of itself.
The kind of cast Iron one uses for engine blocks (nodular/ductile--strength) is not the same as the cast Iron one wants for brakes (grey--machinable, wear resistant) is not the same as one wants for anvils (white cast iron).
Yes it does and it lands all over that pretty mega dollar wheel as you can see in the picture! Believe it or not that brownish (I would say rust colored wheel, but I'm not that crude) wheel used to be black....
There have been cars and motorcycles made with stainless steel rotors. No one uses them anymore, because they stop like ****.
The rotors in that photo must have been sprayed with salt water.
Last edited by Red Mist Rulz; Jul 17, 2020 at 08:35 PM.
Not sure why no one seems to have noticed post #15, but if you spray the stuff in the link below on your rotors after washing and while still wet, you can eliminate this problem. A small bottle of the concentrate is probably a year's supply or more if you wash twice a month or so. I learned about it on a Porsche forum.
You'll still have brake dust w/ Z51 performance-oriented OEM Brembo pads, but your rotors won't rust if left wet after washing. You can do the same thing by driving the car immediately after washing, but the rust happens quickly before the car even dries.
Believe it or not that brownish (I would say rust colored wheel, but I'm not that crude) wheel used to be black.... 
