19/07/2017 12:45pm
There have been two principal materials used for their production in recent years. Cast Iron and Stainless Steel.
Cast iron is very cheap to produce and produces very good friction coefficients but it is also fragile, it is not compatible with many modern pad materials, particularly sintered pads, it is heavy and of course it rusts. Grey cast iron discs can shatter and ductile cast iron is fragile, very fickle with pads and in our experience can warp very easily. We distributed a range of discs made from ductile cast iron for several years and had to return far too many that were warped. The answer usually came back that the problem had occurred due to the use of inappropriate pads but the truth is it happened far too often! Some companies still believe it is the right material to use but there are just too many negatives and not enough positives.
Stainless steel on the other hand, although a little more expensive has a lot more positives. It doesn’t rust, or at least not to any great extent. It is very robust, it is tolerant to almost all brake pads and particularly to sintered_brake_pads. It is highly resistant to wear, it doesn’t shatter and it resists heat very well. When it was first used the friction coefficients were not as good as cast iron and this convinces some that cast iron is still the right material. But I asked a Brembo executive about it some years ago and he said, that was true 30 years ago but the friction coefficients of stainless_steel_discs and sintered_pads went past cast iron around 20 years ago! As usual, for proof he pointed to the race results and pointed out that with the exception of carbon discs in GP, every race bike fitted with Brembo brakes for the last 20 years or so had used stainless_steel_discs not cast iron. Since they are the winning brakes in almost every major championship year in year out it is difficult to argue. The exact specification they use has never been released but it is made specially for them.
So, in modern times at least stainless steel is definitely the way to go but you still need to take care what you buy. After all wood is a very good material to make a boat from. The Spanish armada thought so but you can also make a toy boat from balsa wood. One you can fight a war in and the other wouldn’t last 20 minutes in a duck pond. There are wooden boats and there are wooden boats!