Pads for AP Racing 4-pot RD42 (CP3215 D40/D42).

1. Project Mu PCR09

   11 options · from $387 · 1 in stock

   Project Mu’s Club Racer. A strong trackday pad, but with a 300°C floor it is the range’s worst choice for a cold first lap.

   300–800°Cµ 0.42–0.55Needs heattrackday · circuit

2. Project Mu H20

   5 options · from $525

   A sprint and flying-lap compound used in GT and NASCAR classes.

   200–800°Cµ 0.42–0.44Needs some heatsprint · circuit

3. Circo M119

   1 option · from $508

   Circo’s sprint answer: around 0.5 friction from 50°C, so it works before the pads are hot. Rally and circuit.

   50–800°Cµ 0.48–0.51Usable from coldrally · circuit · sprint

4. Project Mu H16-03

   3 options · from $470

   Project Mu’s GT and TCR-level race compound.

   200–650°Cµ 0.45–0.60Needs some heattrackday · circuit

5. Project Mu H21

   3 options · from $572

   Circuit and endurance racing. Project Mu rate it as kind to the rotor with long pad life.

   200–850°CNeeds some heatcircuit · endurance

6. Project Mu H22

   3 options · from $525

   The rear-axle partner to H20, H21 and H16-03, chosen for low wear.

   Operating range not published

   circuit

7. Project Mu H27

   1 option · from $691

   A low-volume compound Project Mu publish no figures for. Ask us before ordering.

   Operating range not published

Figures are the manufacturers’ own published data for each compound. Where a brand doesn’t publish a figure we say so rather than estimate it. From cold is our reading of each manufacturer’s published minimum operating temperature, not a separate rating they publish. Manufacturers test on their own equipment, so friction numbers are best compared within a brand rather than across brands. Not sure which suits your AP Racing 4-pot RD42 (CP3215 D40/D42) setup? Ask BuildBot or email us with your car, class and typical session length.