I recently bought replacement AP discs for my Son's Big brake conversion on his Subaru Impreza WRX which I am helping him to convert into a trackday car. When they arrived and I had a good look at them I noticed on each one bare metal sections on the outside of the fins. This must be where metal is machined off for balancing? The problem is they do not re-annodise or re-paint the bare metal so an obvious potential for quickly going rusty once they get wet! I am suprised at this oversight by AP considering the cost of them.I had to mask off and paint the affected places as I dont want them going rusty. Anyone else noticed this on their new AP discs?

 

yeah mine were same and full outside of disc aswell were its vented... i found alot of this type of stuff is like compomotive alloys i found there lashed over paint wise shitty finished for what there cost but there said when i contacted them there a competition alloy like that matters like

 

I don’t believe discs are coated, the temperatures they reach it would last 2 mins.
Its only the outside face that would get wet when the car is parked and discs are cold anyway !
After washing the car, drive it a mile and all brakes will be dry.

 

When you look at the new AP discs the fins section to me looks like it is annodised or heat treated, you can see clearly the sections which have been machined off is bare metal which stands out and looks different to the the rest of the fins.

 

Is it not the difference between the cast finish and machined finish.

 

anodising is a process for aluminium.

Bake discs are not anodised, and racing discs like AP....rust like feck if left.

 

Agreed 👍🏻

 

That is what I am saying, you can see clearly the sections on the fins which have been machined back to bare metal for balancing which look nothing like the finish on the rest of the fins.Probably nothing to worry about but I have painted the bare metal sections with high temperature paint.

 

Yes visually different, but the cast is bare metal anyway.