page_title: Disc brake
section_title: Brake disc
hierarchical_section_title: Disc brake / Brake disc
caption_attribution_description: Subject: Upgraded disc brake (283 mm) in my Peugeot 106 Author: Luc106 Date:November 14th, 2015 I release all rights in the public domain. Licensing I, the copyright holder of this work, release this work into the public domain. This applies worldwide. In some countries this may not be legally possible; if so: I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.
context_page_description: A disc brake is a type of brake that uses the calipers to squeeze pairs of pads against a disc or "rotor" to create friction. This action slows the rotation of a shaft, such as a vehicle axle, either to reduce its rotational speed or to hold it stationary. The energy of motion is converted into waste heat which must be dispersed.
  Hydraulically actuated disc brakes are the most commonly used form of brake for motor vehicles, but the principles of a disc brake are applicable to almost any rotating shaft.
context_section_description: The brake disc (or rotor) is the rotating part of a wheel's disc brake assembly, against which the brake pads are applied. The material is typically gray iron, a form of cast iron. The design of the discs varies somewhat. Some are simply solid, but others are hollowed out with fins or vanes joining together the disc's two contact surfaces (usually included as part of a casting process). The weight and power of the vehicle determines the need for ventilated discs. The "ventilated" disc design helps to dissipate the generated heat and is commonly used on the more-heavily loaded front discs.
  Discs for motorcycles, bicycles, and many cars often have holes or slots cut through the disc. This is done for better heat dissipation, to aid surface-water dispersal, to reduce noise, to reduce mass, or for marketing cosmetics.
  Slotted discs have shallow channels machined into the disc to aid in removing dust and gas. Slotting is the preferred method in most racing environments to remove gas and water and to deglaze brake pads. Some discs are both drilled and slotted. Slotted discs are generally not used on standard vehicles because they quickly wear down brake pads; however, this removal of material is beneficial to race vehicles since it keeps the pads soft and avoids vitrification of their surfaces. On the road, drilled or slotted discs still have a positive effect in wet conditions because the holes or slots prevent a film of water building up between the disc and the pads.
  Two piece discs (rotors) are a disc where the center mounting part of the disc is manufactured separately from the outer friction ring. The central section used for fitment is often referred to as the bell or hat and is commonly manufactured from an alloy such as a 7075 alloy and hard anodised for a lasting finish. The outer disc ring or rotor usually is manufactured from grey iron but in special applications can be from steel. Originating from Motorsport but now common in high performance applications and aftermarket upgrades. Two piece discs can be supplied as a fixed assembly with regular nuts, bolts and washers or a more complicated floating system where drive bobbins allow the two parts of the brake disc to expand and contract at different rates therefore reducing the chance a disc will warp from overheating. Key advantages of a two piece disc are a saving in critical un-sprung weight and the dissipation of heat from the disc surface through the alloy bell (hat). Both fixed and floating options have their drawbacks and advantages, floating discs are prone to rattle and collection of debris and best for suited to Motorsport whereas fixed is best for road use.
caption: Example of two piece disc in an aftermarket application
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