I found this info on a thread at the apteraforum.com: http://www.apteraforum.com/showthread.p ... 05&page=12From Craig Osterday, the designer of the EV1's brake system.
"The EV1 did have Hydraulic front brakes (standard hydraulic aluminum
calipers), but they were pressurized by a modified ABS6 actuator, which was
activated by the PFE (pedal force emulator). This provided hydraulic
pressure to the front calipers. It was still brake-by-wire, as there was no
direct hydraulic linkage between the pedal and the calipers. The ABS6 was a
motor - ball screw actuator which Delphi used to make, and was on many GM
vehicles. The rear brakes were all electric, using a motor/ball screw
actuation to expand the drum linings (the drum was a special
carbon/metallic/aluminum composite for weight savings. Hope this helps.
And it was a very high-tech car, and a blast to drive. (It even would lay
rubber). The weak link was the batteries. I drove it home when it was 25F,
and barely made the 20 mile drive before the batteries died. Thank goodness
it had REGEN braking to help the charge."
You can also contact the poster of the messages because she has contact with Craig Osterday.