material of 2-piece rear rotor's hat

[maicol76]

I removed my 2-piece rear rotors for replacement discs (mine is Alcon Superkit), then found rear rotor hat's material is steel and front one is aluminium.
I wonder if other company(Brembo, Ap racing, Stoptech and etc) products are like that. I would be grateful if anyone would use BBK to check (by using magnetic)and let me know.

[pbonsalb]

Parking brakes would go through aluminum much faster than steel.

[jritt@essex]

Originally Posted by maicol76

I removed my 2-piece rear rotors for replacement discs (mine is Alcon Superkit), then found rear rotor hat's material is steel and front one is aluminium.
I wonder if other company(Brembo, Ap racing, Stoptech and etc) products are like that. I would be grateful if anyone would use BBK to check (by using magnetic)and let me know.

Some companies use steel in the rear hat assembly for the parking brake. Steel is much harder than aluminum. We (AP Racing by Essex) use aluminum. We've found that:

A) Our track day customers aren't using their parking brake handle for drift mode. As such, you don't need a ridiculously hard parking brake drum. A softer aluminum one works fine, holds the car in place, and lasts for years without issue. As long as the car isn't repeatedly driven with the parking brake applied, wear will be negligible. To my knowledge we've never had a customer in the history of our brake kit program with a specific problem related to our parking brake hat being aluminum. Here's an example of an owner with 5 years and 50,000 miles on his kit on an e90 M3.

B) Aluminum is much lighter than steel, which is why we use aluminum. To us, the substantial weight tradeoff isn't worth a little bit of durability on the parking brake.

C) Some of our customers completely remove their parking brake, and don't view it as at all important or relevant.

StopTech and Brembo use aluminum hats on the vast majority of their rear applications as well, including the M3. Aluminum has been a proven solution for many years, and as long as the owner isn't driving around with the parking brake engaged, it doesn't come up as an issue. Hopefully that helps. Thanks.

[pbonsalb]

Or drifting. Or at least doing some 180s every now and then.

[Richbot]

Some use a ~1/16" thick steel annular insert inside the aluminum hat. I would think there would be some dissimilar metal issues in heavy track use, but for a street kit I've seen this on a few

[jritt@essex]

Originally Posted by Richbot

Some use a ~1/16" thick steel annular insert inside the aluminum hat. I would think there would be some dissimilar metal issues in heavy track use, but for a street kit I've seen this on a few

Yes, some do use that solution.