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Originally Posted by flyingv
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Neat!
That's very similar to the factory firewall to dual masters with balance bar adapter that CNC Brakes used to offer years ago, but the Wilwood piece looks much cleaner.
Rob at No Limit Engineering also used to build something similar (a bolt on 2 bolt factory style master cylinder mount to dual master with balance bar adapter) that had a built in swinging intermediate pivot lever between the factory brake pedal and the dual masters to minimize side loading on the bores of the master cylinders. His adapter offered multiple bolt locations on the intermediate pivot lever to easily alter the pedal ratio without having to redrill your factory brake pedal. Not sure if he still makes it or not, but it was a cool piece.
Wilwood simplified things even further and appears to just have the balance bar sliding in a slot on the adapter to avoid twisting the balance bar and putting excessive side loading on the bores of the master cylinders. The slider might have a little more friction than Rob's swinging pivot lever solution and doesn’t allow easy adjustment of pedal ratio, but I bet the Wilwood piece still works just fine.
While a new pedal assembly with a built in balance bar along with firewall mods is a much cleaner and more compact solution than a firewall adapter that sticks way out, the Wilwood adapter is a great way to see if you like the feel and function of a manual setup with dual masters and a balance bar before you go slicing up the firewall up to install pedals, or if you prefer a "no mod" install.
I had the parts and was ready to slice up my firewall to install a full set of Tilton 600 pedals and 76 series masters for simplicity and a minimal look on the firewall, but when I decided to add ABS I found out that Tilton does not recommend the 76 series master cylinders for use with ABS as the pulsations from the ABS can damage the seals in the master cylinders. For ABS they said to use the 79 series ABS compatible master cylinders which are far more expensive and also have to be used with the far more expensive 800/900 series pedal assemblies, which have their own mounting quirks for a firewall mount setup as the master cylinders now move during the pedal stroke so you need a rubber lined seal plate on the firewall to allow the masters to move. While that’s OK for a race car, on a street car that sounds like an invitation to let hot air and engine noise into the car from leaks around the master cylinder seal plate… so I changed plans.
I'm now going with the DSE booster and master since the master is an OEM GM piece and compatible with ABS, and will have the ECM monitor booster vacuum levels with a late model OEM GM sensor/checkvalve at the booster inlet and the ECM can cycle a Hella UP5X series OEM auxiliary electric vacuum pump when needed to maintain vacuum in the booster. This arrangement of engine vacuum, check valves, and an auxiliary Hella vacuum pump is exactly how GM handled things on the CTS-V / ATS-V / ZL1 with vacuum brake boosters (before they went to the full brake by wire system with electric booster about 2 years ago.) A belt driven vacuum pump off a late model GM pickup would be another good solution as it's silent and wouldn't need any wiring, but it would be difficult to adapt to my Wegner accessory drive. The electric pump setup also has the advantage of being able to cycle and provide vacuum for the brakes even if the engine isn’t running.
When it comes to converting from power to manual brakes, just make sure you do the math for your current caliper piston areas and pedal ratio before converting from power to manual... some calipers with small piston areas just don't play nice in a manual setup, as you might not be able to get a master cylinder with a bore small enough to have reasonable pedal effort with them. A bandaid to that is to use very aggressive high-mu brake pads, but those kinds of pads often come with drawbacks on a street car like being excessively abrasive at lower brake temps which rapidly chews up rotors. A large piston area on the calipers for a manual brake setup gives you the widest options of pedal ratios and master cylinder bore sizes when it comes to dialing in the pedal stroke vs effort “feel” you are looking for.