One of the main things holding people back from upgrading the stock brakes to a BBK on the BMW E89 Z4 is the OEM electronic parking brake system. Since it's a fly-by-wire system, which engages at the press of a button, it wasn't possible to swap the rear calipers without losing the parking brake function.... Until now!

After years of development and testing, our electronic line lock solution is finally ready for market! It's a direct bolt on part and installation couldn't be simpler. No modification is required, nor is any adjustment to the ECU settings. It literally slots straight onto the OEM parking brake motor and is secured in place with two bolts.

The system is priced at GBP390, which is a small price to pay for maintaining a balanced front/rear brake bias. Here is a link to more information and pricing:

They don't look too bad either!...