Double-check my braking plan

[derekf]

Brakes, like so many things on my car, have been up in the air for a long time and a lot of ideas have sounded like the 'proper' way to go. Unfortunately, I don't remember what went with what and why item A was a better idea than item B at the time.



What I've got right now:
Tall (B-body) spindles
Joe's C5 front caliper brackets
93-97 Camaro/C4 rear caliper brackets

The plan:
C5 front calipers (2 40mm pistons) on C5 13" rotor
C4/93-97 Camaro rear calipers (1 40.8781mm piston) on Camaro 11.6" rotors.
15/16" bore master cylinder

Now, I remember reading that the rear piston should be ~60% of the size of the front (but I can't find where I read that so it may be my imagination) and in my searching this morning I found a post that said that the rear piston area should be no more than 50% of the front.

If I break out my rusty math skills, I get 2512mm area for the fronts
(40mm diameter = 20mm radius; 20mm^2 * pi -> 1256mm, *2 for 2 pistons -> 2512mm)
and 1311.75mm for the rear
(40.8781mm = 20.439mm radius; 20.439mm^2 *pi = 1311.75mm)
which would appear to leave the rears at 52% of the fronts.

If y'all would, please a) doublecheck my math, and b) doublecheck my thought process - it's not too late to change directions on this so long as I haven't bought anything expensive.

[Salt Racer]

a) Your math is close enuf (I got 2513.3mm^2 and 1312.4mm^2). I multiply the numbers by two for floating calipers, so effective piston area of 5026.6mm^2 and 2624.8mm^2, respectively.

b) It really depends on the combination of parts you have, so there's no set rule, or set % ratio of rear piston area/front piston area (as far as I know, anyway). A car with super low CG, 65% rear weight bias and 25" front and 32" rear tires will require a lot more brake in the rear than a car with high CG, 58% on nose with same diameter tires all way around, for example.

My rear calipers (1.375" 4-piston) have 62% of total area of my front calipers (1.75" 4-piston). 13"/12" rotors, and 27.2"/28.5" tires, w/ 57% front weight bias. It's basically an oversized A-body w/ big block (Riv is E-body, JFYI). It's been working just fine since I got the rear pressure dialed in.

Not sure about your M/C bore size (depends on pedal ratio and power-or-manual), but otherwise it looks fine to me. Make sure you have some means of adjusting the front/rear brake bias (dual M/C or proportioning valve).

[derekf]

Thanks, Katz.

I'd neglected to add the adjustable proportioning valve I'd planned, or to point out that this is for my '65 Malibu. M/C would be powered - either vacuum-powered or Hydroboosted.

[Salt Racer]

With power assist and pedal ratio of 4:1 or better, you can probably do 1" M/C. But don't quote me...

CarlC has setup somewhat similar to yours on his Camaro (which happens to be one of my fav. Camaros on this site - very clean but he uses it on tracks regularly). Check out his webpage and see what he'd done.

[Hydratech®]

Thanks, Katz.

I'd neglected to add the adjustable proportioning valve I'd planned, or to point out that this is for my '65 Malibu. M/C would be powered - either vacuum-powered or Hydroboosted.

IF you end up going the hydraulic assist route, note that master cylinder bore sizing is very pleasantly de-emphasized quite a bit, due to the unique characteristics of their functions. For instance, a 15/16ths bore mc would be a general candidate for manual usage vs your combo, a 1" bore would be a general candidate with the vac assist, and with hydraulic assist, you could actually run a range of 1" to 1 1/8" bore with spectacular results. If you were to install one of our systems, I'd steer you towards the 1 1/8" bore...

[blown66chevelle]

please school me on joes c5 brake brackets, havent been on line hear for a while ,i must have missed this, thanks dwayne

[dennis68]

Joe's brake bracket to fit the C5 caliper onto B spindles can be seen below....