That is a good question. Right now we have no plans to go with another parking brake caliper though.
We originally designed the rear parking brake setup to use an internal drum setup, but after hearing about a couple issues with that setup on the other rear kit, we went back to an individual caliper for the parking brake. We have used several of the Wilwood parking brake calipers on custom setups before including mechanical spot calipers like in your picture and the MC4 and have always preferred the MC4 over the mechanical spot calipers for a couple reasons. The MC4 is basically a floating setup that is very easy to adjust by the end user and setup properly, also the attachment point for the cable is more secure than the mechanical spot calipers we have used. The MC4 is also a lot simpler in operation than the internal drum and easier to install. Wilwood does list the MC4 as maxing out at 12.88" and we are using it on a 14" rotor, however we do have it mounted so that there is plenty of clearance from the caliper to the rotor and also the pad is in complete contact with the rotor and does not hang off of the rotor at all. Typically the reason you limit a caliper to a certain size rotor is for those reasons. Also, since the center of force of the pad is further out on the rotor, there is a torque advantage when applied vs. the center of force closer to the center of the rotor. We have also used the MC4 on other custom setups with larger than 12.88" rotors before and they work fantastic. We will be doing more testing on the setup though before it is released and will make sure that it can lock up the rear while at speed, hold the Slingshot on steep hills, etc. If this parking brake setup does not perform atleast as good as stock, we will ditch it and probably just go back to the internal drum setup we already prototyped also.
Hope that helps,
Dave
Dave@DDMWorks, are there any further developments or info on this?
