J Hook Discs are the latest disc face design by AP Racing. Vagbremtechnic adapted the initial design onto OEM discs for the following reasons.
1.They give improved bite
2. For high temperature track day use they give better debris clearance and reduces distortion / vibration.
For road use we decided to opt for the version where the outer grooves do not run out to outside diameter but stay within the confines of the disc face. For road applications they also generate less noise than straight or curved groove discs and don't suffer the fatigue cracking that drilled disc users can experience after many heat cycles.
So win win for J hook, Vagbremtechnic also take a non handed OEM casting and Left/Right the J Hook pattern to ensure temperature stability and an appropriately designed disc face for either the nearside or offside of the car to give a good gas path despite not using a handed casting. We've seen some real success on a budget with these discs especially when used with a four piston caliper upgrade.
Where they really come into their own though is when theyre combined with a more capable set of brake pads - this is a real track day enabler and we find customers finding other weaker areas of their car such as tyres and suspension now that their car stops reliably again and again. J hook is the homologated disc face for BTCC and has been for three years.