I ordered an
AP Racking BBK from Essex, the ones based on the Radi-Cal Pro 5000R calipers and J Groove discs.
I will keep the rears stock, though I am using the ECS Tuning 2 piece rear rotors.
I will run Ferodo DS1.11 pads on the fronts, and DS2500s on the rears for the track, then swap out the DS1.11 fronts for DS2500s for street usage. I figure if I keep some "trackable" pads as my street pads, in a pinch I can use them on the track. I'm not married to Ferodos, just there is a local racer supply shop that stocks them and I like to support local where I can.
It turns out that I experienced what felt like knockback, but was actually an issue with the DS2500 fitting into the front caliper(s??). Some folks here had a thread about it, and that is what helped figure it out. When I put the Hawk HPS 5.0 pads back on, the brakes feel good for street usage.
For me, the stock BMW Z4M brakes are not adequate for this car and how I drive on the track. I will run the AP Racing BBK on the track in about 10 days.
I may one day swap out the rear brakes for an AP Racing BBK, but that would really be more about convenience for pad changing and aesthetics than a performance gain worth the cost. But uh... those J Groove discs and nice calipers would look good front and rear
Thanks for the guidance, and the thread that helped sort out why my brakes were shite. This community is an invaluable Z4 owner resource.
Cheers,
Eamonn