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 The Evolution of Brake Rotors: From Cast Iron to Carbon Ceramic, and Understanding the Differences

The Evolution of Brake Rotors: From Cast Iron to Carbon Ceramic, and Understanding the Differences

We often have clients coming in with carbon ceramic braking systems installed in their cars, asking for some clarity on the differences between traditional cast iron or steel rotors and carbon ceramic rotors.
To understand it, we would break it down into four significant points before finally diving into the cost:

1. Heat

Brake discs/rotors under heavy use are subject to very high temperatures. This is especially true on the track where temperatures can reach upwards of 400+ degrees, three times more than daily driving. When heated for prolonged periods, cast iron can be prone to distortions and begin presenting disc inconsistencies.

If the disc becomes warped due to overheating, this can result in vibration when braking. Once this occurs, the only remedy is to replace the rotors to stop the vibration/shuddering under braking. Alternatively, carbon ceramic rotors can operate at much higher temperatures for extended periods, dissipating heat much better than cast iron, making rotor distortion a thing of the past. Minimal thermal expansion is the name of the game here.

2. Brake fade

Brake fade is the sudden reduction of stopping power. Brake fade has several causes, all of which are more common on cast iron rotors. When operating at above-optimal temperatures, the brakes can temporarily and permanently underperform. The brake feel will diminish, and braking performance will be lost.

The leading causes are overheating brakes above optimal temperatures, brake fluid boiling (or vapour lock), and improper pad/rotor interaction due to improper bedding of brakes causing glazing (something we will need to cover in more detail in a separate post).

3. Weight savings

Cast iron rotors are much heavier than carbon ceramic rotors. This lowers the car’s unsprung weight, helping with performance in multiple areas. Unsprung weight is the weight that is not supported by the suspension. This all comes down to the principles of inertia. Handling and ride quality are much improved as the suspension has less weight to manage and can react more quickly to changes in inertia. The lighter unsprung weight in carbon ceramic rotors also means less rotational weight is present when coming to a stop when braking and less weight to move when accelerating.

While the braking system is only a part of the picture, adding carbon ceramic brakes significantly lowers a vehicle’s unsprung weight.

4. Durability and longevity

The durability and longevity improvements with carbon ceramic rotors are dramatic, up to 3 times longer, generally speaking. If cast iron rotors’ lifespan typically lasts from 50,000 to 100,000 km, carbon ceramic rotors can last anywhere from 150,000 km to 250,000 km and beyond. Of course, this will vary significantly on driving patterns, but one can expect the rotors to be good through the life of the first ownership cycle.

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All the positives do come at a cost, quite literally. The price, in comparison with traditional cast iron rotors, is astronomic, to put it mildly. One can expect starting prices for OEM rotors to cost $5,000 apiece. As an example, a recent Mercedes-Benz E63S was quoted $12,000 on parts alone for a pair of rotors, and this is just for the rear! The first owner may never incur the replacement cost due to the longevity of the carbon ceramic brakes on OEM vehicles.

Subsequent owners, on the other hand, must take caution. Factor in the potential costs of replacement, and, of course, INSPECT THE BRAKES pre-purchase.

Conversely, if you have carbon ceramic rotors installed on your vehicle, and your brakes become due, get a second option if quoted for the rotors. Remember this general rule of thumb. When optioned with carbon ceramic rotors, brake pads should be the only thing needed on the braking system for the first 150,000 km under typical driving conditions.

So in summary, are carbon ceramic brakes better? In almost every foreseeable way, that’s a hard yes! But when factoring in the cost when they become due, that answer isn’t so clear.

For more information, feel free to contact us with any questions.

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