Painting Rotor Hats...

[91redFox]

Hey guys,

This thread may be repetitive, but I've searched endlessly and cannot find what I'm looking for.

I recently bought new cross drilled and slotted rotors for my cobra brakes and, like many, I plan on painting the hats and outside edges to prevent rust and corrosion.
However, the rear rotors (ordered from the same company) are zinc plated, while the front are not.
I want to paint the front to keep them from rusting on non-contact areas, but would like the rear to match.
Have also heard the coating doesn't last very long...
Does anyone have any experience with painting over zinc plating?
I'm assuming I will have to etch the plating with scotch-brite then prime and paint, but I wanted to see if anyone else had done so before.

Thanks in advance!

 

[cobra1965]

Just buy some high temp paint, your color choice and clean them up really good and paint them..

 

[squeak93]

Some will flame me for this but I don't tape anything off. I just spray the whole rotor face/edges with a high temp paint (usually duplicolor engine enamel) and then let the pads remove the paint where they ride. This keeps you from having unsightly rust rings and makes both the hats and edges look clean.

If you dd or see a lot of rocky roads then expect chips. But for a non dd car or weekend warrior I've had great success.

 

[91redFox]

Thanks for the replies!
It is a weekend car, so it shouldn't be a problem.
As far as the painting goes, I was worried about the paint not sticking to the zinc plating on the rear rotors.. Do you guys have any experience with this?

 

[MFE92]

Some will flame me for this

And for good reason. The pads won't scrape the paint off in one pass like some putty knife on wet paint. They'll wear it off, but not before a hole bunch of that's not supposed to be there gets embedded in the surface of the pads.

 

[mikestang63]

Some will flame me for this but I don't tape anything off. I just spray the whole rotor face/edges with a high temp paint (usually duplicolor engine enamel) and then let the pads remove the paint where they ride. This keeps you from having unsightly rust rings and makes both the hats and edges look clean.

If you dd or see a lot of rocky roads then expect chips. But for a non dd car or weekend warrior I've had great success.

Really really bad idea. The paint will junk up the pads and then get ground into the pads and rotors. There is a reason the rotors are machined and the pads need to be installed clean. There will be no way those pads will properly setup.

But a can or spray or brush on caliper paint and do it right the first time.

Oh, and drilled rotors are not only a waste of money, they crack and can literally break (not brake) into pieces. If you bought a set of cheap Ebay rotorsm send them back. A good set of blanks are all that is needed for most street cars with a set of Hawk pads.

 

[91redFox]

Oh, and drilled rotors are not only a waste of money, they crack and can literally break (not brake) into pieces. If you bought a set of cheap Ebay rotorsm send them back. A good set of blanks are all that is needed for most street cars with a set of Hawk pads.

Waste of money? They dissipate heat and improve braking performance...
I can assure you they are not cheap ebay rotors lol
I do lots of "spirited" back roads driving and hard cornering and thought I would benefit from the cross drilled rotors.
My car has had CD rotors on it for years while being autocrossed by the guy that had it before me, without any issues, still have the same ones in it today. Also felt I would be "downgrading" by going from cross drilled rotors to blank ones.

 

[Mustang5L5]

Waste of money? They dissipate heat and improve braking performance...

No, they don't.

This is a big misunderstanding on the purpose of crossdrilled rotors. The holes are there to allow gases venting from race pads to escape. This is why they were typically seen on mostly exotic supercars using race or semi-race type pads. Since most street pads do not vent gases, they are not needed and typically just for show. The crossdrilled rotor "fad" was simply people looking at high end cars and saying "I want that too".

As for cooling, the way a rotor cools is that the central vanes pump cool air outwards through centrifugal force through the center of the rotor and pick up heat and expel it outwards. This is why brake cooling ducts dump air as close as possible to the backside of the rotor where the vanes can pick up this cool air and pump it through the rotor internally. The crossdrilled holes are perpendicular to this airflow and do now contribute significantly to any cooling effect.

In fact, the crossdrilled holes reduce mass and force the heat in the rotor to concentrate in the mass that does remain, increasing heat in the rotor. If the rotor wasn't drilled, the heat would be spread out and absorbed more into the rotor mass that would be present reducing the number of rotor hot spots which leads to less pad material being transferred to the face of the rotor and leads to the build up of Cementite which reducing braking ability in the rotor.

DO not compare exotic, race-type brake systems on Lambo's and Porsche's which are designed from the beginning with different materials and the holes cast into them, as well as more exotic brake pad materials to standard passenger car Ebay rotors with holes drilled into them. They are nowhere near engineered the same way. Most often people claiming a braking "improvement" do so simply because they replaced worn out brake parts, loaded up with Cementite.

Cross-drilled rotors look nice and all, but that's about it. Anyone doing serious AutoXing or Road-Racing will advocate quality plain-faced rotors for best cooling, reliability and function.

 

[mikestang63]

No, they don't.

This is a big misunderstanding on the purpose of crossdrilled rotors. The holes are there to allow gases venting from race pads to escape. Since most street pads do not vent gases, they are not needed and typically just for show.

As for cooling, the way a rotor cools is that the central vanes pump cool air outwards through centrifugal force through the center of the rotor and pick up heat and expel it outwards. This is why brake cooling ducts dump air as close as possible to the backside of the rotor where the vanes can pick up this cool air and pump it through the rotor internally. The crossdrilled holes are perpendicular to this airflow and do now contribute significantly to any cooling effect.

In fact, the crossdrilled holes reduce mass and force the heat in the rotor to concentrate in the mass that does remain, increasing heat in the rotor. If the rotor wasn't drilled, the heat would be spread out and absorbed more into the rotor mass that would be present reducing the number of rotor hot spots which leads to less pad material being transferred to the face of the rotor and leads to the build up of Cementite which reducing braking ability in the rotor.

DO not compare exotic, race-type brake systems on Lambo's and Porsche's which are designed from the beginning with different materials and the holes cast into them, as well as more exotic brake pad materials to standard passenger car Ebay rotors with holes drilled into them. They are nowhere near engineered the same way. Most often people claiming a braking "improvement" do so simply because they replaced worn out brake parts, loaded up with Cementite.

Cross-drilled rotors look nice and all, but that's about it. Anyone doing serious AutoXing or Road-Racing will advocate quality plain-faced rotors for best cooling, reliability and function.

Mike, could not have said it better.

Drilled rotlors on 99.999% of cars is for looks. Oh, let us know when you need to get those rotors turned.Not many shops will turn them.

 

[Jersey Joe]

Turn rotors? Who does that anymore?

 

[Boosted92LX]

No, they don't.

This is a big misunderstanding on the purpose of crossdrilled rotors. The holes are there to allow gases venting from race pads to escape. This is why they were typically seen on mostly exotic supercars using race or semi-race type pads. Since most street pads do not vent gases, they are not needed and typically just for show. The crossdrilled rotor "fad" was simply people looking at high end cars and saying "I want that too".

As for cooling, the way a rotor cools is that the central vanes pump cool air outwards through centrifugal force through the center of the rotor and pick up heat and expel it outwards. This is why brake cooling ducts dump air as close as possible to the backside of the rotor where the vanes can pick up this cool air and pump it through the rotor internally. The crossdrilled holes are perpendicular to this airflow and do now contribute significantly to any cooling effect.

In fact, the crossdrilled holes reduce mass and force the heat in the rotor to concentrate in the mass that does remain, increasing heat in the rotor. If the rotor wasn't drilled, the heat would be spread out and absorbed more into the rotor mass that would be present reducing the number of rotor hot spots which leads to less pad material being transferred to the face of the rotor and leads to the build up of Cementite which reducing braking ability in the rotor.

DO not compare exotic, race-type brake systems on Lambo's and Porsche's which are designed from the beginning with different materials and the holes cast into them, as well as more exotic brake pad materials to standard passenger car Ebay rotors with holes drilled into them. They are nowhere near engineered the same way. Most often people claiming a braking "improvement" do so simply because they replaced worn out brake parts, loaded up with Cementite.

Cross-drilled rotors look nice and all, but that's about it. Anyone doing serious AutoXing or Road-Racing will advocate quality plain-faced rotors for best cooling, reliability and function.

I get the idea of not using cheap ebay stuff, but does this statement mean don't buy drilled rotors period? Because every high end brake company out there sells them. Baer, Wilwood, Aerospace.. does this mean these are all snake oil.... or are you just saying don't buy ebay rotors? You mention Lambo and exotic race type equipment.. would these fall into that category?

 

[Mustang5L5]

I get the idea of not using cheap ebay stuff, but does this statement mean don't buy drilled rotors period? Because every high end brake company out there sells them. Baer, Wilwood, Aerospace.. does this mean these are all snake oil.... or are you just saying don't buy ebay rotors? You mention Lambo and exotic race type equipment.. would these fall into that category?

Those would fall in that category as well being an engineered system. If I wasn't on a cell phone is explain why. I'll update when back on a PC.


I was more or less talking about going out and buying a Nissan Maxima and tossing on a set of oem style cross drilled rotors and expecting an improvement.


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