The compound
Circo S99.
Circo’s entry-level racing compound, also used in 2WD rally. It works from 100°C to 700°C — enough range for club racing without the cold-lap penalty of a full race compound.
Operating range100–700°C
Friction µ0.40–0.43
Pad lifeSame - no numeric figure published.
Cross-brand equivalents
Run something similar.
These are the compounds we stock for the AP Racing 6-pot RD54 (with tab) whose published friction and operating temperature come closest to Circo S99. They are a starting point for switching brands — not a guarantee of identical feel, because each manufacturer measures friction on their own equipment.
WinmaX W5
Very close100–750°Cµ 0.40–0.43
WinmaX’s standard circuit model, and the default club racing and rally choice in the range.
Matched on published friction and operating temperature.
From $405Project Mu H21
Partial match200–850°C
Circuit and endurance racing. Project Mu rate it as kind to the rotor with long pad life.
Matched on published operating temperature only — one of the two brands doesn’t publish a friction figure, so this is a weaker comparison.
From $656Project Mu H21-07
Partial match200–850°C
An endurance compound developed for GT and Porsche one-make racing.
Matched on published operating temperature only — one of the two brands doesn’t publish a friction figure, so this is a weaker comparison.
From $890Compare every compound for the AP Racing 6-pot RD54 (with tab)
Fits the same caliper
More pads for the AP Racing 6-pot RD54 (with tab).
Pairs well with
