930 Calipers - Factory Finish

[martin_gibson]

Can anyone clarify what factory finish (if any) was applied to the Turbo 930 calipers?

Thx

Martin
911SC 3.6

[Porsche virgin]

I suppose it was different from year to year. Mine were from a '78 and are yellow.

Hope this helps.

[martin_gibson]

They are 89 930 calipers and I am getting some conflicting advice suggesting that they were either painted (type?) or anodised at the factory?

Thx

[Steve@Rennsport]

Martin.

These came black anodized.

[rsrfan]

The calipers on my 86 930 were black anodized at the factory. I have NEVER seen factory painted 930 calipers.

JP

[martin_gibson]

Originally Posted by Steve@Rennsport

Martin. These came black anodized.

Steve,

Great, appreciate the clarification.

I have access to a local anodiser, so how should he best approach preparation(media blasting?) and re-anodising of the calipers whilst ensuring that the piston bores are protected?

Thx

Martin

[Steve@Rennsport]

Originally Posted by martin_gibson

Steve,

Great, appreciate the clarification.

I have access to a local anodiser, so how should he best approach preparation(media blasting?) and re-anodising of the calipers whilst ensuring that the piston bores are protected?

Thx

Martin

Martin,

We use soda blasting to clean the calipers before re-anodizing and rebuilding them. Its a totally benign process thats FAR better than anything else.

[martin_gibson]

Originally Posted by Steve@Rennsport

We use soda blasting to clean the calipers before re-anodizing and rebuilding them. Its a totally benign process thats FAR better than anything else.

Steve,

Forgive my ignorance, but how do you protect the piston bores during soda blasting then anodising or are the pistons left in-situ?

Thx
Martin

[Steve@Rennsport]

Originally Posted by martin_gibson

Steve,

Forgive my ignorance, but how do you protect the piston bores during soda blasting then anodising or are the pistons left in-situ?

Thx
Martin

I leave the pistons in place during this process but the soda medium will not hurt the bores at all.

[RWebb]

huh - I guess the bores are hardened or plated?

[martin_gibson]

Originally Posted by Steve@Rennsport

I leave the pistons in place during this process but the soda medium will not hurt the bores at all.

....and ditto during anodising?

[Steve@Rennsport]

Originally Posted by martin_gibson

....and ditto during anodising?

Nossir. The caliper pistons are first extracted and then anodizing is done with the calipers empty.

[martin_gibson]

Originally Posted by Steve@Rennsport

Nossir. The caliper pistons are first extracted and then anodizing is done with the calipers empty.

Steve - that's clear now - thanks for your help, much appreciated - Martin

[Steve@Rennsport]

Originally Posted by RWebb

huh - I guess the bores are hardened or plated?

Nope, they are not,...

Soda blasting is a very gentle process if its done properly.

[89911]

This is pretty much the finish. An anodized, black-grey look. I like it and wouldn't paint them

[fredmeister]

What are the pistons made out of for these 930 calipers? They appear to be bronze not stainless steel.
Also, are there any seals to replace in the piston bores as they don't look like they have a protective outer rubber seal like other Porsche calipers?
I used to rebuild my A-calipers in my 911SC almost twice a season because DE days would destroy the seals with heat.

[Steve@Rennsport]

Originally Posted by fredmeister

What are the pistons made out of for these 930 calipers? They appear to be bronze not stainless steel.
Also, are there any seals to replace in the piston bores as they don't look like they have a protective outer rubber seal like other Porsche calipers?
I used to rebuild my A-calipers in my 911SC almost twice a season because DE days would destroy the seals with heat.

They are hard anodized aluminum and have 2 seals for each piston: one is a hydraulic seal and the other is a wiper.

Your seal issues were all about excessive heat and thats cured by larger brakes that have more thermal dissipation capacity.

Brake cooling kits certainly help but when one is cooking the seals, its time for bigger brakes.

[KFC911]

If ya want bling, here's mine (sourced from Steve W) painted with the two part caliper paint from our host:

[martin_gibson]

Originally Posted by Steve@Rennsport

Soda blasting is a very gentle process if its done properly.

Next question: having just dismantled the (89) turbo hubs (presently painted red) and the rotors (rusty) should I apply the same process (soda blast & anodise) as per the 930 calipers - clearly I would not anodise the rotors.

Thx

Martin

[KTL]

Anodizing is typically done with aluminum alloys since they respond best to it. It's also done with titanium, magnesium, beryllium,......... but not iron. Keith's picture above your post shows plated rotors. That would be the way to go. Point being is rotors are actually treated in some cases. As far as anodizing goes, it's purpose is to establish a protective layer of iron oxide that is very hard. If you did anodize an iron rotor, it may be undesirable since the hard surface might not have desirable friction properties? Zinc plating works good because it wears off easily where in contact with the pads and the remaining non-pad contact areas stay looking good for a while. Turns out iron is not a good candidate for anodizing anyway. The process causes expansion of the metal and the resulting iron oxide layer forms cracks & then flakes off, thereby defeating the purpose of anodizing it in the first place!

You could anodize the front hubs, plate the rotors and paint the hubs. The anodizing for the hubs should be thin so it doesn't make it difficult to install the bearing races. For the rear hubs, plating them may prove troublesome since the plating will add thickness and make the press fit into the wheel bearing even tighter. The plating would likely chip off. That's why i'd paint them with high temp enamel instead.