Types of Discs: Technical Comparison

Although all brake discs fulfill the same basic function, differences in their design and manufacturing significantly affect their performance, especially in the context of sports discs for cars.

Solid (smooth) discs

Solid discs, also known as smooth or conventional discs, are the most basic and common type, especially on the rear axles of many vehicles or in mid-low range cars.

Design: Completely smooth braking surface.

Advantages:

• Pad durability: With no irregularities, the pad wears more evenly and slowly.
• Quiet: They produce the least noise.
• Cost: They are the cheapest to manufacture and replace.

Disadvantages:

• Heat dissipation: Their ability to dissipate heat is the most limited. Under intensive use, they are prone to fade and warping.
• Gas and debris evacuation: They lack mechanisms to evacuate gases generated by the friction of the pad at high temperatures (causing a pillow effect) or to clean debris from the pad.
• Not suitable for extreme sports driving: Their thermal performance makes them unsuitable for continuous, high-demand braking.
• Recommended use: Daily cars with gentle driving, rear axles of vehicles with ABS/ESP, or applications with low braking demands.

drilled discs

Drilled discs feature holes on the braking surface. This design is aesthetically appealing and often associated with high-performance vehicles.

Design: Multiple holes evenly distributed across the braking face.

Advantages:

• Heat dissipation: The holes act as small conduits that increase heat dissipation surface area and facilitate the evacuation of gases generated by the pad (the "degasification" phenomenon).
• Pad cleaning: They help clean the pad surface by removing debris, improving the coefficient of friction.

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• Sporty appearance: They offer a very aggressive and sporty aesthetic.
• Improved initial bite: They can provide a more direct pedal feel and a sharper initial bite due to the "cut" in the pad material.

Disadvantages:

• Structural fragility: The holes can create stress points that, under extreme and repetitive thermal cycles, may lead to the development of cracks or fissures, especially around the edges of the holes.
• Faster uneven pad wear: They tend to wear the pads more quickly and irregularly.
• Noise: They may produce slight noise or whistling during braking.

Recommended use: Moderate sporty driving on roads and occasional track days where aesthetics are a factor. Not recommended for intense racing due to the risk of cracking.

Slotted discs (ridged)

Slotted discs, also known as slotted, feature grooves or channels that run across the braking surface. This is a very popular design in racing.

Design: Slots (straight, curved, or J-shaped) machined into the braking surface, without penetrating completely through the disc.

Advantages:

• Gas and debris evacuation: The slots are highly effective for evacuating gases formed between the pad and the disc at high temperatures and for cleaning pad debris. This maintains a more constant coefficient of friction and reduces fade.
• Crack resistance: Since they are not through-holes, they better preserve the structural integrity of the disc, being less prone to cracking under thermal stress than drilled discs.
• Aggressive bite: They provide a very aggressive and consistent initial bite.
• Cooling: The slots also help dissipate heat by increasing the contact surface with the air.

Disadvantages:

• Faster pad wear: Like drilled discs, they tend to wear pads faster than smooth discs.
• Noise and vibration: They can produce more noise (a characteristic hum) and a slight vibration in the pedal compared to smooth discs.
• Recommended use: Intense sporty driving, frequent track days, and racing, where fade resistance and consistency are prioritized over comfort and pad durability.

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