Hi Guys - Hope you don't mind the thread hi-jack (Thought I'd keep the info together rather than start a new thread - but if that what you'd prefer, let me know and I will)...
I'm just going through this at the moment - have put AU2 front calipers (twin 40mm pistons) and (some other - known but ashamed
) rear discs from hoppers stoppers. The kit came with a generic 7" dual diaphragm booster and bracket and XB 1" dual circuit master.
The supplied bracket / booster combo aims the pushrod just above the brake pivot pin. Now most power/boosted setups have a pedal ratio of 4-4.5:1 - the 64-66's is 6:1 (This is more in line with manual brakes.) . Installed and brakes worked fantastically, but pedal travel was 3/4 the way to the floor (In line with the above statement about pedal ratio).
Changed the booster / bracket combo back to my original ( the one with the lever arm). This bracket doubles your mc travel compared to straight through, but requires double the effort - in effect turning the pedal ratio to about 3:1
( Note that This bracket is about 30mm longer than the non-lever one (as shown on page 1 of this thread), and to put the dual booster on, the master would hit the shock tower.)
Now the brakes work pretty well, with really short pedal travel, but I feel that I'm a bit below where the braking should be with twin 40mm pistons and 330mm discs on front.
I'm considering having my master sleeved to bring it down to 7/8", which would put me just about smack on the 4 ratio - and should give me more stopping at the expense of a bit more travel (that I have plenty in my sleeve)
My 2 questions are :
1) How much does that brake pin bracket shown by ausfox on p1 alter the pedal ratio ( I may consider re-installing the generic dual diaphragm booster and bracket if that changes the swept length enough (Although not too keen as that will increase the angle of the pushrod into the booster)
2 I think I have picked up in this thread that the lever bracket ( travel/force multiplier) is for manuals, but auto's have a straight pushrod from pedal to master. If so - how do they get enough travel not to have a spongy pedal with the 6:1 pedal ratio - because I believe that it is the one pedal for all 64-66 mustangs - or am I mistaken and there is an auto/power pedal out there with a lower pin ?
Thanks
Dave