JCC asked me about my floater axle, and we got to talking brakes, and he suggested I post about my brakes.

Front:
Dr Diff kit - Gen III viper front calipers on SRT8 14.1x1.25" rotors. The rotors weigh about 27 pounds each (!), and the hubs are aluminum. The kit uses 73+ disc brake spindles and a caliper mounting bracket he makes. The brakes fit inside factory GT500 wheels (18x9.5 with 45mm offset). This wheel also fits around the tie rod end, which allows for the 7.2" of backspace. *With this combo, the tire hits the frame before lock on my duster.

Rear:
Schreiner Enterprises 9" floater using 5x4.5" hubs, Coleman 14x1.25" rotors, Gen III viper front calipers, and brackets I made. I went with a floater axle so I could run 4 piston calipers and not worry about pad knockback. The brackets consist of cut down GM Metric caliper brackets bolted to 1.25x1.25x8.5" aluminum stock. The caliper brackets run a full 360* around the axle - made for a much easier job!

Pads:
Cadillac CTS-V factory pads - they are branded "Brembo", and are a Ferodo HP1000 compound (same compound that probably all 'brembo' branded pads use, including the new Camaro, Viper, and high end exotics). The CTS-V pads are .300" taller than the viper pads, otherwise they are the same dimensions. They are the same size pad used on the Viper ACR-X, which uses these exact calipers. The pads fit height-wise on my rotors (just barely). They cost less than Viper brembo pads, though some aftermarket pads cost more in this size (vs viper size). I will probably have to stagger the pad compound to get the bias right, but I'll wait to fix it once I know I have a problem.

Master cylinder: 15/16" from Dr Diff. Manual. Should be about right, but if not, I'll change it out.

Wilwood proportioning valve - I'll probably need all 58% reduction in line pressure to get close to the right bias at threshold braking. With sticky tires, I'll end up with a more aggressive pad in the front.

The car isn't running, but I'll report back once it is, let ya'll know how this thing stops. The goal of the car is to run with a C6 Z06 and porsche GT3 on a road course.

Pics:

Nice!!

any reason why you went with the same size caliper in the back instead of running the Gen 3 rear viper calipers, which are also a 4-piston design that looks like the fronts, but with smaller pistons.

I put gen 2 front brakes on all 4 corners on my Dakota, with 13" rotors (same bolt pattern as Viper) but I have factory RWAL that keeps me from locking up the rears. --and it works great despite the RWAL being designed for a disc/drum system.

I bought a set of 4, and they ended up being two sets of fronts. Not a huge difference in volume (4.3 sq/in vs 3.9 sq/in).

Same brakes I have in the front.

How much room did you have on the spindles?

When I did my 8 piston calipers on the same diameter rotor it was a really tight fit. There was only one place I could mount the calipers and that spot allowed about 1/2" of wiggle room. The lower ball joint, upper control arm, and sway bar prevented stuffing it anywhere else.

I kept my TSM rear lower bracket adding spacers to bring them into position. The biggest difference being that I kept the 8-3/4" rear end.

Thanks for making me have brake envy.

We have built similar set-ups on other cars, and unfortunately with e 15/16" M/C and no help behind it, you will drive it the first time and most likely it will not stop! We learned our lesson a while back.... This type of set-up could need hydraboost and some other type of unique boosting system.

Let us know if it works out as-is.

I use a manual 1-1/8" MC from a D150 and it works great. The pedal feels great. It's a bit lighter than the factory manual drums but not as soft as a typical power brake system.

My caliper volume is different than the Viper setup but it still demonstrates the ability to use a common manual MC on a big brake system.


When fitting my calipers, I mounted a rotor, wired it to prevent movement, and wedged a caliper in place using the brake pads and wood shims. Running the suspension through the full range of motion including steering angles put the caliper in it's place. I have about 1/4" of clearance to the upper control arm and about that much between the lower inner edge of the caliper and the ball joint arm.

I got lucky. Fitting those things had not even crossed my mind when I dropped the cash for them.

My front calipers have two 28mm and two 32mm pistons per side. The total volume is less than you'd think.
The rears use 28mm and 30mm pistons. Again, fairly low volume.

The manual master has a 1-1/8" bore.


If you're getting more than .010" pad movement then something is wrong. Brake pads normally ride a couple thousandths of an inch off the rotor. Anything more will lead to a squishy pedal.

Thanks for pointing out the MC error!

Quote:

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To determine if the MC is too small, look at the pressure generated vs the pad movement.
High pressure at low movement = too small.
Low pressure at high movement = too large.

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Any rule of thumb for the above rule?

I found an interesting point of reference offered by Mark Williams:
http://www.markwilliams.com/braketech.aspx

Rule of thumb from their website:
9.6 sq in = 7/8 MC
14.4 sq in = 1" MC
19.2 sq in = 1 1/8 MC

From what Feets is describing I need a larger master than my 15/16". I need to push pretty damn hard on the pedal to get a hard stop.

Rule of thumb?

Well, who's thumb are you using? My thumb is likely different than yours.

The feel is a personal thing.
As a general rule you want about 1000 psi of pressure at the caliper.
Now to put a wrench in things...

When you have a longer lever arm (read larger diameter rotor) you won't need quite as much pressure. It's like having a longer wrench. You don't need to pull as hard to get the same torque.

That means you can use a bit less pressure with larger diameter rotors. What doesn't change is pad movement.
To get an idea how far your pads move, run the numbers on your stock stuff. Try to work out similar pad movement at a reasonable pedal travel and pressure.


Clear as mud?

i think the book was "driving to win by jackie stewart?"

research concluded that a driver could mentally modulate leg power better if it dident have movement in the equation so cars were setup with as solid a brake peddle as possible.a driver could "hit" the peddle with a more accurate amount of force without movement in the brain as well.

does this aply to our cars or gocarts on steroids where mechanicle advantage may not be nessesary i have no idea.i have however puty a big bore aluminum mas cyl on a 4 wheel drum 69 dodge truck,the peddle felt like it bent more than it moved it seemed like i could stop perfectly on a mark with it stopping.it was just an experiment, i changed it back before i sold it.

i wonder how much leg power factors into this,8 months ago i was leg pressing 1000 lbs.i had to stop leg training due to hitting my knee REALLY hard on the asphalt and after that all lifts felt really spooky.i kept waiting for it to go away but it wouldent.about three weeks ago i just said o well and started leg work again.after a couple leg workouts it feels fine but the presses have been kept under 800lbs.leg feels fine so ill be strong again in no time

Do whatever you want on your car but I'm not going to live with a solid brake pedal.

Pressing 300 lbs on your brake pedal to stop the car at every red light and stop sign would get old VERY quickly. Think about it. How many one leg 300 lb presses can you do? Now, how many times do you hit the brakes on your way to work? No matter how He Man you think you are I bet the brake pedal would still win.
It would also be hard on the seat frame and floor.

Some people forget that we drive these cars for pleasure.