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So. I took this out of the shop today and I didn't even feel comfortable leaving my neighborhood. The pedal feels bled, but must be pressed as hard to the floor as possible to stop. I don't mean that it's hard to press, simply that it does nothing for the first 3/4 travel.
This is stock calipers, pads ( all new), earls hoses, all new lines front and rear. I moved the pivot point about an inch.
I wonder if the ratio isn't providing enough travel?
So. I took this out of the shop today and I didn't even feel comfortable leaving my neighborhood. The pedal feels bled, but must be pressed as hard to the floor as possible to stop. I don't mean that it's hard to press, simply that it does nothing for the first 3/4 travel.
This is stock calipers, pads ( all new), earls hoses, all new lines front and rear. I moved the pivot point about an inch.
I wonder if the ratio isn't providing enough travel?
-- Joe
If you have stock, from the factory calipers, they are LOW drag and need a step bore master cylinder to function correctly. This is why you get about 3/4 of travel before you get some pedal pressure. LOW drag calipers require more fluid to work correctly. The strait bore 1.03" bore master cylinder included in the kit is filling up the LOW drag calipers first, then starting to apply pressure in the system after the calipers fill up with the volume of fluid they need.
These calipers are NON low drag, normal calipers and will work with strait bore master cylinders.
Once you get the AFCO calipers installed, you will have a very firm pedal, but with the large bore master cylinder, your brake system will may build pressure to effectively stop the car. If this is the case, you may need to reduce the size of your master cylinder to a 7/8" bore or 24mm bore depending on what rear brakes you are using.
What is your rear brake setup? If disc, what rear caliper are you using?
If you have stock, from the factory calipers, they are LOW drag and need a step bore master cylinder to function correctly. This is why you get about 3/4 of travel before you get some pedal pressure. LOW drag calipers require more fluid to work correctly. The strait bore 1.03" bore master cylinder included in the kit is filling up the LOW drag calipers first, then starting to apply pressure in the system after the calipers fill up with the volume of fluid they need.
These calipers are NON low drag, normal calipers and will work with strait bore master cylinders.
Once you get the AFCO calipers installed, you will have a very firm pedal, but with the large bore master cylinder, your brake system will may build pressure to effectively stop the car. If this is the case, you may need to reduce the size of your master cylinder to a 7/8" bore or 24mm bore depending on what rear brakes you are using.
What is your rear brake setup? If disc, what rear caliper are you using?
Hello,
I ordered some speedmaster calipers which are supposedly not a low-drag design:
Measure the outside diameter of the pistons of the ACFO calipers just to make sure they are 2.75". I don't have experience with the AFCO version, but the CPP Big Bore calipers I bought a few years ago did not measure out to 2.75" (measured about 2.56"). I know the Wilwood 2.75" diameter piston calipers are in fact 2.75", because I have used them in the past.
Can you post up pictures of those calipers once you get them?
I have used those calipers with a 7/8" bore master cylinder and had good results.
The 1.03" bore master cylinder that you have will give a firm pedal, but the clamping force at the front and rear calipers will be low and you most likely find it hard for the car to stop.
I would start with a 7/8" bore master cylinder and if you feel that you are not getting the volume you need, step up to a 24mm or 15/16" bore master cylinder. Smaller bores will give you higher brake line pressure and more clamping force at the calipers.
Double check your pushrod alignment with your current setup. Because of the design of the 3rd and 4th gen F-body's brake pedal assembly, the brake pedal arm is pointing strait down at the floor board when it is not being pressed. If your push rod is set up going strait into the master cylinder when the brake pedal is not being pressed, then the piston travel of the master cylinder will be reduced as the brake pedal is pressed.
As the brake pedal goes through its range of motion, the pin in the brake pedal arm that the push rod attaches to will arc up and away from the master cylinder piston. It is easier to see this than write about it. Bottom line is that at the end of the pedal stroke, your brake pedal will be moving 2 to 3 inches, but your master cylinder piston will not be moving much at all.
The push rod will need to be level with the piston of the master cylinder when it is at the end of the pedal stroke. The stroke of the master cylinder piston only needs to travel about 1 inch in distance to supply the volume of fluid needed for the calipers.
I would set up the pin location on your pedal like this. This will be easier to do with the pedal assembly out of the car and the manual brake conversion mocked up on the bench.
1. Have the brake pedal at the resting (NON pressed) position.
2. Unhook the pushrod from the master cylinder.
3. Using a long, thin wood dowel (about the same diameter as the push rod), have the wood dowel come strait out of the master cylinder. Wood dowel should be positioned against the center of the master cylinder piston.
4. Mark on the wood dowel where it intersects the middle of the pedal arm.
5. Remove the wood dowel and measure one inch on the dowel from where you marked on the dowel. Make the one inch mark towards the direction of the master cylinder piston.
6. Install the wood dowel back up against the piston like it was previously and have it come strait out the back of the master cylinder centered on the master cylinder piston.
7. Press in the brake pedal.
8. While keeping the dowel level with the master cylinder, mark on the brake pedal arm where the middle of the dowel intersects the brake pedal arm at the one inch mark.
9. This is where you should drill your hole for your pin.
What I wrote is most likely clear as mud. Let me know if you have additional questions.
I have used those calipers with a 7/8" bore master cylinder and had good results.
The 1.03" bore master cylinder that you have will give a firm pedal, but the clamping force at the front and rear calipers will be low and you most likely find it hard for the car to stop.
I would start with a 7/8" bore master cylinder and if you feel that you are not getting the volume you need, step up to a 24mm or 15/16" bore master cylinder. Smaller bores will give you higher brake line pressure and more clamping force at the calipers.
Double check your pushrod alignment with your current setup. Because of the design of the 3rd and 4th gen F-body's brake pedal assembly, the brake pedal arm is pointing strait down at the floor board when it is not being pressed. If your push rod is set up going strait into the master cylinder when the brake pedal is not being pressed, then the piston travel of the master cylinder will be reduced as the brake pedal is pressed.
As the brake pedal goes through its range of motion, the pin in the brake pedal arm that the push rod attaches to will arc up and away from the master cylinder piston. It is easier to see this than write about it. Bottom line is that at the end of the pedal stroke, your brake pedal will be moving 2 to 3 inches, but your master cylinder piston will not be moving much at all.
The push rod will need to be level with the piston of the master cylinder when it is at the end of the pedal stroke. The stroke of the master cylinder piston only needs to travel about 1 inch in distance to supply the volume of fluid needed for the calipers.
I would set up the pin location on your pedal like this. This will be easier to do with the pedal assembly out of the car and the manual brake conversion mocked up on the bench.
1. Have the brake pedal at the resting (NON pressed) position.
2. Unhook the pushrod from the master cylinder.
3. Using a long, thin wood dowel (about the same diameter as the push rod), have the wood dowel come strait out of the master cylinder. Wood dowel should be positioned against the center of the master cylinder piston.
4. Mark on the wood dowel where it intersects the middle of the pedal arm.
5. Remove the wood dowel and measure one inch on the dowel from where you marked on the dowel. Make the one inch mark towards the direction of the master cylinder piston.
6. Install the wood dowel back up against the piston like it was previously and have it come strait out the back of the master cylinder centered on the master cylinder piston.
7. Press in the brake pedal.
8. While keeping the dowel level with the master cylinder, mark on the brake pedal arm where the middle of the dowel intersects the brake pedal arm at the one inch mark.
9. This is where you should drill your hole for your pin.
What I wrote is most likely clear as mud. Let me know if you have additional questions.
I put about 32 ounces of fluid through this bleeding all 4 corners, yet the pedal is very soft. I had someone push on the brakes while I had a 3 foot bar on the lug studs. If the pedal is to the floor as hard as possible, I can't turn the wheel with the bar. Any less and I can.
I will check the rod tomorrow, but I'm at a loss here. I expected a more firm pedal.
Any chance the rear PBR brakes are causing an issue?
The calipers measure out to 2.55/2.56, about .200 larger than stock.
-- Joe
The stock calipers have a 2.5" piston, need to measure it further down. The piston is stepped. Likely need to do the same with the AFCO caliper piston.
The stock calipers have a 2.5" piston, need to measure it further down. The piston is stepped. Likely need to do the same with the AFCO caliper piston.
RBob.
Hi RBob,
I wasn't aware of that. Perhaps they are in fact 2.75" then. The stock pistons (at the pad end) measured about 2.36", so either way they are bigger.
I bled and bled and bled these things, but I still have a soft pedal and it doesn't clamp unless I hold it to the very bottom. I double checked my rod, and it is 1" higher than the stock which should be 6:1 ratio, but either way the problem seems more like air trapped.
If you moved the push rod up on the pedal with out moving the master cylinder up on the firewall, the last half of your pedal stroke it not moving the master cylinder piston much at all because the the pin that holds the push rod to the pedal is moving up and away from the master cylinder piston.
Your pushrod will need to be in a strait line (inline) with the master cylinder piston when the brake pedal pad is pressed about 5 inches from its resting (unpressed) position. You will have a slight downward angle to the push rod when the pedal is in its resting position and when the pedal is in its fully pressed position, the push rod will be inline with the master cylinder piston. This is the only way you will get the inch of travel needed to move the volume of brake fluid needed to fill the calipers up with fluid.
If you moved the push rod up on the pedal with out moving the master cylinder up on the firewall, the last half of your pedal stroke it not moving the master cylinder piston much at all because the the pin that holds the push rod to the pedal is moving up and away from the master cylinder piston.
The BMR bracket doesn't move it up. I did notice that your manual brake thread has the master mounted along the top two bolts, where the BMR and other kits seem to be slightly lower.
I checked my rod again. I did drill the hole 1" up as per BMR instructions. I was tempted to try it in the stock location, but found out tonight that I can't even get the rod to angle down low enough to go to the stock location.
I can measure the travel tomorrow. You say an inch total?
From your picture, it looks as if the pushrod is in the correct location for your setup
I'm wondering if maybe the master is just bad. I cam push the pedal all the way with my hand without much effort.
I saw you posted this on your thread:
Originally Posted by malibudave
Wilwood-120-8924 has a 2.75" diameter piston and is NON low drag. These WILL NOT work with 7/8" bore master cylinders. A 7/8" bore master cylinder cannot supply the volume of fluid needed for the larger piston. A 24mm is the smallest you can use with this caliper.
So, assuming RBob is correct and I measured the caliper wrong, I cannot use a 7/8" bore master. I could try a 24MM master today:
Part Number: NM1983
Weight: 4.08lbs
Warranty: Limited Lifetime
Application: Except Turbo
With 15" wheels
Notes: With reservoir
Installation Hardware Included: Yes
Item Grade: OEM Standard
Master Cylinder Bore Diameter (in): 0.9439
Master Cylinder Color / Finish: Metallic
Master Cylinder Material: Aluminum or Cast Iron
Master Cylinder Port Sizes: Primary 0.375"-24 , Secondary 0.375"-24
Master Cylinder Reservoir Included: Yes
Package Contents: New Brake Master Cylinder, Reservoir, Bleeder Kit
Product Condition: New
To test your current master cylinder, plug both ports of the master cylinder and slowly pump the pedal. If the pedal gets very firm with little movement, hold the pedal down with some pressure for about 45 seconds. If it slowly sinks to the floor, it is bad.
For aluminum master cylinders, use the following part numbers:
These master cylinders have 3/8-24 inverted flare outlets.
Dorman M39451 is a 7/8" bore ALUMINUM master cylinder
Cardone 132412 is a 24mm bore ALUMINUM master cylinder
Joe, it isn't going to be that the MC bore is too small. A smaller bore will move less fluid and put the pedal further down to the floor.
Most likely there is air trapped someplace in the system. A couple of years ago I went through the same thing on a manual brake 4 wheel disc car. No amount of pedal pumping, vacuum bleeding, or gravity bleeding would get the air out.
Had a low soft pedal. I finally built a pressure bleeder and that did the trick. During bleeding a fine stream of the smallest bubbles I've ever seen was exiting the system.
Pressurized at 15 psi the fluid was moved rather quickly though the system. This allowed it to compress the air bubbles and move them out.
Joe, it isn't going to be that the MC bore is too small. A smaller bore will move less fluid and put the pedal further down to the floor.
Most likely there is air trapped someplace in the system. A couple of years ago I went through the same thing on a manual brake 4 wheel disc car. No amount of pedal pumping, vacuum bleeding, or gravity bleeding would get the air out.
Had a low soft pedal. I finally built a pressure bleeder and that did the trick. During bleeding a fine stream of the smallest bubbles I've ever seen was exiting the system.
Pressurized at 15 psi the fluid was moved rather quickly though the system. This allowed it to compress the air bubbles and move them out.
RBob.
This is very embarrassing but I think I figured out the problem.
I bought a new 24mm master today, and started taking the rod off the pedal to dissasemble. I noticed that my pedal was returning about 3/4" away from the brake light switch. I found it odd, but thought nothing of it initially.
I removed the master from the firewall and went to pull the rod out and I couldn't. I had to put the master in a vise and slide-hammer it out.
It then dawned on me, when i initially put the rod in it wasn't seated all the way. The rubber gromet just behind the ball was keeping it from seating. The first hard pump with the pedal seated it, and thereby reduced the travel of the brake pedal.
My guess is that it was getting maybe 1/2 the travel it was supposed to.
Compounded by the fact that I initially "bench bled" it hooked to the firewall with a pedal, I probably never got all the air out of it.
I decided to move forward and install the 24MM (.944") master. (the original was 1.032".
You're suggesting I use my pneumatic brake bleeder? How did your pressure bleeder work?
Otherwise I was gonna wait for the wife to get home tonight and ask her to kindly sit in the vehicle for an hour again
So the heim joint itself is just junk. It's hard to rotate, so when the bolt is tight it doesn't return the pedal all the way. If you leave the bolt loose, it rotates around the pedal returns fine.
10-28-2015, 01:09 PM
