Painting Genuine Mercedes discs

[bikes & cars]

I have bought a set of genuine mercedes discs for my sl350, the discs are supplied painted in a grey "protective" coating.

I am going to spray paint the discs with VHT paint before I fit them, my question is has anyone else done the same thing, did you remove all of the grey "protective" coating before you painted them with a VHT paint or did you spray the VHT paint directly over the grey paint that,s on them.

also any recommendations on which VHT spray paint is best for the job

thanks in advance

 

[MancMike]

Leave the protective coating on, it's designed to be worn off by the pads. (mine said specifically on the packaging)

Don't get your additional paint on the friction area of the disc, so mask it off if you can. You can use your old disc to know where the friction area is, and transfer the measurements across.

I changed my pads and discs all 'round last weekend, and that coating will be gone the first time you use the brakes.

I've sprayed bare discs in the past on the non friction areas to stop them going rusty brown, but I didn't bother with these, as that coating should last a while, I think that's it's purpose. (on the non-friction areas). Time will tell!

 

[whitenemesis]

^^^^ what he said, leave the grey coating on. Mine are rust free with no special treatment..

 

[brucemillar]

Fit the discs drive the from 20mph to abut 117mph check that the brakes are all OK then apply paint.

I painted mine with smooth Hammerite.

 

[BTB 500]

Yup I used silver smooth Hammerite on the hub part of my SL disks ... worked perfectly, and no visible rusting.

 

[noogieman]

smooth Hammerite spray paint, is it heat resistant?

painting hub in silver gives a nice look.
is there heat resistant gloss Hammerite spray paint to protect hub from brakedust after painting hub with silver?

the upper part of the disc where the round edges of the disc is going, where the cooling vents are.
would you paint this section in silver to keep away from rust?

would you paint the inside/backside of hub to prevent from rust?

 

[brucemillar]

I just painted the center hub section on my C55 discs. I did with a brush and smooth Hammerite gold. Paint on, leave for a few hours then drive. The heat bakes it like enamel. Still there two years later.

 

[flango]

You shouldn't paint the hub it affects brake performance as that is one route that heat dissipation is channelled

If you look on YouTube you will see the thermal studies of the heat flowing from the disc into the hub and away

 

[BTB 500]

You shouldn't paint the hub it affects brake performance as that is one route that heat dissipation is channelled

If you look on YouTube you will see the thermal studies of the heat flowing from the disc into the hub and away

Painting the rim of the hub could indeed slightly reduce the amount of heat radiated from there. But so long as you don't paint the mating surface, the disk is still bolted directly to a large chunk of metal (the wheel) which acts as a pretty good heatsink. If heat radiation was a significant factor the hub part of the disk should have a black surface finish ... don't think I've ever seen this? Of course that's why car radiators are painted black.

High performance brakes have carbon etc. discs which aren't an integral part of the hub anyway.

 

[BTB 500]

I just painted the center hub section on my C55 discs. I did with a brush and smooth Hammerite gold. Paint on, leave for a few hours then drive. The heat bakes it like enamel. Still there two years later.

Yup I only did the visible part of the hub on my SL (thin coat, brushed on) ... purely for cosmetic reasons. This was when I fitted the AMG wheels, which expose the disc hubs more than the Ceginus ('Evo') ones it had on before. Done 7 years ago now, no problems.

 

[flango]

Painting the rim of the hub could indeed slightly reduce the amount of heat radiated from there. But so long as you don't paint the mating surface, the disk is still bolted directly to a large chunk of metal (the wheel) which acts as a pretty good heatsink. If heat radiation was a significant factor the hub part of the disk should have a black surface finish ... don't think I've ever seen this? Of course that's why car radiators are painted black. High performance brakes have carbon etc. discs which aren't an integral part of the hub anyway.

All serious performance discs, rotors and hub are finished in Matt black steel for this exact reason. No need for it on a road car I agree, when I had my brake upgrade done it was AP that told me not to paint them and the reason why and I never have. Not had any issues with the brakes either even on the ring under extreme conditions

 

[hotrodder]

Of course that's why car radiators are painted black.

While black paint will be better than light colours with regards to thermal radiation, paint of any colour adds a layer of insulation to the part...
Whether the radiator (heat exchanger)* is in a house or car the bulk of heat transfer occurs via convection and conduction, relatively little by radiation
Radiators are painted mostly for corrosion protection and appearance

All serious performance discs, rotors and hub are finished in Matt black steel for this exact reason. No need for it on a road car I agree, when I had my brake upgrade done it was AP that told me not to paint them and the reason why and I never have. Not had any issues with the brakes either even on the ring under extreme conditions

How do you make a steel cast iron brake disc matt black? Or matt grey? The various coatings used on brake discs are done by several methods which are effectively paint most of the time...
A zinc phosphate treatment followed by painting with an epoxy E coat or a single step self phosphating E coat. Automatic E-coat facility, Electrocoating, E Coating
ATE talk about a paint system with an aluminium base ATE Brakes -Original ATE brake discs probably something similar to GEOMET® 360 which also hints at the other reason things like radiators are painted... the coating hinders heat transfer less than corrosion
Brembo bigging up the corrosion resistance of their UV coating paint compared to other E coats and zinc passivation https://www.brembo.com/en/Press/Com...ati Stampa 2012/Brembo_UV_Coated_Discs_EN.pdf

* same deal with the A/C evaporator except it works 'backwards' and water-oil heat exchangers work the same way too... convection from fluid to the surface the tube, conduction through the tube and into the fins and then convection from the tube/fin surface to the other fluid whether it's a liquid or a gas

 

[flango]

As I said MOC makes them black all the way through

 

[hotrodder]

So you're claiming that cast iron brake disc is

black all the way through

and it's not a coating that wears off the friction surface leaving the coating (E coat, black phosphate etc) to continue to provide some corrosion protection on the unswept areas?

 

[flango]

No the disc is not made out of cast iron, carbon steel or stainless steel. I would have to check the actual composition of the disc but they are definitely black all the way through been using them on race cars for years

 

[hotrodder]

So it's of zero relevance to an OEM cast iron disc for a road car that was painted for corrosion protection as part of the manufacturing process then

 

[flango]

So it's of zero relevance to an OEM cast iron disc for a road car that was painted for corrosion protection as part of the manufacturing process then

If you read my post I said it was for specialist performance and race cars and not suitable or applicable to OEM parts and road cars

At no point did I Indicate or imply the discs I was talking about were cast iron, as a qualified metallurgist that would have been pretty stupid

 

[hotrodder]

I did read what you posted, origionally you said (my bold)

All serious performance discs, rotors and hub are finished in Matt black steel for this exact reason. No need for it on a road car I agree, when I had my brake upgrade done it was AP that told me not to paint them and the reason why and I never have. Not had any issues with the brakes either even on the ring under extreme conditions

before back pedalling when called out

as a qualified metallurgist that would have been pretty stupid

Keep going...

 

[flango]

Those that know me on here know my capabilities and experience for those that don't know me I couldn't give a toss about their opinions. Life's not a popularity contest

 

[optimusprime]

info

Disc painting is a must to stop rust building up on the outer rim ,and on the hub part .I have done my car .The old ones i took off were rusty on the edge and in the centre. Dont paint the face that contacts the alloy wheel , but a little copper slip is what it will need .So removal of the rim will be easy next time you remove it... The spray paint i used was anti rust.. mask off before ypu paint them .Your like me , as i wanted to paint them so i did.