I've dealt with the "not being able to lock up" issue a few years back. Ultimately found that manual brakes do not work well on heavy street cars (>3500lbs) unless you do one or more of the following:
Disclaimer; I also have big sticky Toyo’s on a 3800lb car. Lighter car, set-up and smaller less sticky tires will lock-up sooner.
Yes pad Cf is a huge factor but...if the extra pad Cf doen't do it for ya here is more info. Ceramic pads are only for show because of no dusting. Not too good at stopping.
*
Higher Caliper pressure (1000psi min..1500+ ideal based on 4sq in caliper) required for pad Cf below .4 (street pads)
I used Willwood’s BP30's (.5-.6Cf) on 13" rotors, SL6's and 3/4 master. That locked them up! Stopped the car perfect, (to my liking) but at the expense of major dusting, squealing and rotor degradation. Needless to say I removed them. Oh yea. pad knockback started on the rear rotors with the Ford 9” due to the small master. Now I'm using power assist with large 1 3/16 master and Wilwood BP10’s. (.4Cf) Will put you through the glass..and lock up if I so choose.
*
Increase Pedal Ratio Currently running 4:1 power assist and have run up to 6:1 and 8:1 for the previous manual system to try and get more caliper pressure.
*
Larger Diameter Rotors (i.e. 13 to 14" nets approx +10% rotor braking torque)
*
Power brake assist Just a hunch, but if you don’t like the higher pad Cf’s to get your desired braking, you’ll be switching over.
Good Web Calc:
http://www.jakelatham.com/radical/in...culators.shtml