What is the difference between street, sport and track brake pads?
Every pad compound is a compromise between friction, temperature range, wear, noise and dust. A pad that is strong at 600 °C is usually weak and noisy at 50 °C. The right pad is the one whose operating window matches how the car is actually driven.
What a pad is made of
A brake pad is a steel backing plate carrying a friction material: binders (phenolic resins), fibres, abrasives, lubricants such as graphite, and fillers. The recipe decides how much grip the pad generates at a given temperature, how fast it wears and what it does to the disc.
Street pads are usually NAO (non-asbestos organic) or so-called ceramic compounds: quiet, low dust, gentle on discs, and effective from cold. Sport pads are typically semi-metallic or higher-carbon blends: more friction and a wider temperature range, at the cost of dust and noise. Track pads use high-temperature resins or sintered metallic compounds built to keep their friction level at disc temperatures a street pad would never see.
Friction coefficient and the edge code
The friction coefficient (μ) is the ratio between the force pressing the pad onto the disc and the braking force it produces. Many pads carry an SAE J866 edge code: two letters printed on the edge of the pad. The first letter is the friction measured at normal temperature, the second at elevated temperature: D = 0.15–0.25, E = 0.25–0.35, F = 0.35–0.45, G = 0.45–0.55, H = above 0.55. A typical street pad is “EE” or “FF”; many race pads are “GG” or higher.
The code is a coarse classification from a standard test, not a performance guarantee. Two “FF” pads can behave differently at the edges of their range, so the manufacturer’s friction-versus-temperature curve is more useful when it is published.
The operating window
Every compound has a temperature range in which μ is stable. Below it, the pad bites weakly; above it, resins break down, μ drops and the pedal stays firm while the car stops less — pad fade. Street pads are designed for cold bite and moderate temperatures; track pads for high, stable friction once hot. A track pad used cold on the road gives long stopping distances on the first stop of the morning, squeals, and wears discs faster.
Practical rules
Same compound on both wheels of an axle, always.
Changing compound on one axle only changes brake balance between front and rear. On cars with ABS and stability control this is managed, but the feel changes; on track it can change how the car rotates under braking.
New pads need bedding: a series of progressively harder stops without coming to a full stop, to lay an even film of pad material on the disc. Skipping it is a common cause of judder later (see hot spots).
Dust is not a quality indicator. Aggressive compounds dust more because they work partly by abrasion.
For a car that sees occasional track days, the usual answer is a street or sport pad on the road and a dedicated track pad fitted for the event, with fresh high-temperature fluid.