600 Re-branded as Radi-CAL™ R2 - Silver bottle with Blue cap. R2fluid has a dry boiling point exceeding 300°C and has been developed for racing applications where high temperatures are being experienced, e.g. when using carbon discs and the ultimate in brake fluid performance is required. It should be noted that before using R2fluid, any existing brake fluid should be drained completely from the brake system. The system should be thoroughly purged with new R2 and can be filled completely with new R2 fluid.
- Recommended Shelf Life The recommended shelf life of an unopened fluid bottle is 18 months. AP Racing recommend any fluid manufactured after that time to be disposed off and not used.
Research has shown that the relationships between problems reported and properties identified may be expressed as follows:-
- Long /Spongy Pedal a) Compressibility, up to three times that of glycol based fluids b) High viscosity, twice that of glycol based fluids, leading to slow rates of fill and retention of free air entrapped during filling, and hence bleeding difficulties.
- Sudden loss of brakes a) Air absorption. Gasification of absorbed air at relatively low temperature produces vapour lock effect. b) Immiscibility (failure to mix) with water. Whilst the presence of dissolved water will reduce the boiling point of glycol based fluids any free water entrapped in silicone-filled systems will boil and produce vapour lock at much lower temperatures (100°C or thereabouts)
- Hanging on of brakes a) Low lubricity. In disc brake systems the sole mechanism for normalisation of system pressure upon release of pedal pressure is a designed-in tendency of seals to recover to their ‘at rest’ attitude. Low lubricity works against this tendency. b) High viscosity exacerbates the effect of (a) above. It should not be assumed, therefore, that the high price of silicone fluids implies higher performance in hard driving or even normal road use.