Description
Radi-Cal R4 boasts the highest dry boiling point of any racing brake fluid currently available (340 deg C) and offers outstanding resistance to vapor lock / pedal fade under the most arduous of conditions. A higher vapor lock point means a firmer brake pedal at the extremes of brake temperature.
Radi-Cal brake fluid has enhanced lubricity which increases the life of metal moving parts within the brake system and increases efficiency.
'Typical' Boiling Points.
- New Dry 340°C.
- 'Wet' E.R. 195°C
500ml Bottle
To view the AP Catalogue, click Here
Servicing & Replacement Guide
AP Racing’s competition guidance is essentially: bleed the system immediately before each event, ideally using fluid from a new, sealed container. R4 is hygroscopic, so once opened it begins absorbing moisture, which progressively reduces its boiling point.
A practical race-car schedule would be:
- Before every race meeting: Bleed each caliper until fresh, bubble-free R4 is coming through. This is particularly important after a hot previous event.
- Full fluid replacement: I’d recommend a complete flush with fresh R4 at the start of the season, and again during the season depending on event frequency and brake temperatures.
- After overheating/boiling the brakes: Replace the fluid before the car runs again. Don’t just bleed a small amount from the calipers.
- Opened bottles: For critical race use, don’t rely on R4 that’s been sitting around opened for months. AP specifically recommends fresh fluid from a previously unopened container for maximum performance.
- Never reuse bled fluid.
R4 has a very high dry boiling point of 340°C, but its quoted wet boiling point is around 195°C. That difference is exactly why keeping moisture out of a race-car system matters.
