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Topic Review (Newest First)
02-18-2016 10:07 AM
malibudave I submitted a double post.
02-18-2016 10:04 AM
malibudave Below is an analysis using the Brake Torque Calculator found on Pro-Touring.com. This calculator will give you an idea of what brake torque is for a certain front and rear setups. I am just going to show the changes from the stock front g-body brake system and compare them to a Blazer dual piston brake swap, a stock LS1 Camaro brake swap, a LS1 Camaro brake swap with Corvette calipers

Page 7, Post #140

Brake sizing and selection tutorial featuring Ron Sutton and Tobin of KORE3 - Page 7
This entire post is a really good read if you are interested about brakes.


Here are the inputs that are the same for ALL different types of brake systems shown below.
• 6 to 1 pedal ratio
• 26” tall tire
• 100 ft/lb pedal pressure
• Manual Brakes – NO POWER ASSIST
• Pad Coefficient of Friction - .45
• Use of stock type (tandem) master cylinder

__________________________________________________ __
Stock G-body/S10/3rd Generation F-body Front Brake System
• Rotor Diameter – 10.5”
• 7/8” Bore Master Cylinder Area - .601 sq-in
• Line Pressure – 998 psi
• Front Caliper Piston Area – 4.909 sq-in
• Front Clamping Pressure – 4899 pounds
Front Rotor Torque – 964 ft/lb
• Tire Forces – 890 lb
__________________________________________________ __
Stock LS1 Camaro/Firebird Front Brake System
• Rotor Diameter – 12”
• 7/8” Bore Master Cylinder Area - .601 sq-in
• Line Pressure – 998 psi
• Front Caliper Piston Area – 4.931 sq-in
• Front Clamping Pressure – 4921 pounds
Front Rotor Torque – 1107 ft/lb
• Tire Forces – 1022 lb
__________________________________________________ __
Stock LS1 Camaro/Firebird Front Brake System with Corvette Calipers with 7/8” bore master cylinder
• Rotor Diameter – 12”
• 7/8” Bore Master Cylinder Area - .601 sq-in
• Line Pressure – 998 psi
• Front Caliper Piston Area – 3.994 sq-in
• Front Clamping Pressure – 3986 pounds
Front Rotor Torque – 897 ft/lb
• Tire Forces – 828 lb

Stock LS1 Camaro/Firebird Front Brake System with Corvette Calipers with 21mm bore master cylinder
• Rotor Diameter – 12”
• 21mm Bore Master Cylinder Area - .537 sq-in
• Line Pressure – 1117 psi
• Front Caliper Piston Area – 3.994 sq-in
• Front Clamping Pressure – 4461 pounds
Front Rotor Torque – 1004 ft/lb
• Tire Forces – 927 lb

__________________________________________________ __
Stock Blazer Twin Piston Front Brake System
NOTE: The Blazer twin piston front calipers have a piston area too large to run a .875” bore master cylinder. These calculations are using a 24mm bore master cylinder.
• Rotor Diameter – 10.75”
• 24mm Bore Master Cylinder Area - .701 sq-in
• Line Pressure – 856 psi
• Front Caliper Piston Area – 5.152 sq-in
• Front Clamping Pressure – 4410 pounds
Front Rotor Torque – 889 ft/lb
• Tire Forces – 821 lb

Stock Blazer Twin Piston Front Brake System
NOTE: The Blazer twin piston front calipers have a piston area too large to run a .875” bore master cylinder. But to show the differences between the systems, these calculations are using a .875” bore master cylinder.
• Rotor Diameter – 10.75”
• 7/8” Bore Master Cylinder Area - .601 sq-in
• Line Pressure – 998 psi
• Front Caliper Piston Area – 5.152 sq-in
• Front Clamping Pressure – 5142 pounds
Front Rotor Torque – 1036 ft/lb
• Tire Forces – 956 lb


Rating from best to worst:
1. LS1 Camaro / Firebird stock front brakes with 7/8" bore master cylinder.
2. Blazer Twin piston stock front brakes with 7/8” bore master cylinder. NOTE: This setup will not work with a 7/8” bore master cylinder.
3. LS1 Camaro / Firebird front brakes with Corvette brake calipers and a 21mm bore master cylinder. NOTE: A 21mm master cylinders are fairly rare and hard to find.
4. Stock g-body/S10/3rd Generation F-body stock front brake system with 7/8" bore master cylinder.
5. LS1 Camaro / Firebird front brakes with Corvette brake calipers and a 7/8” bore master cylinder.
6. Blazer Twin piston stock front brakes with 24mm bore master cylinder.
12-07-2015 10:30 AM
malibudave Manual brake installation with adapter plate painted satin black to match firewall better.

08-27-2015 02:00 PM
malibudave Caliper Update:

I have found a good NON low drag (normal) bolt in replacement brake calipers for stock front brake systems. These brake calipers can be used with strait bore (normal) master cylinders and step bore master cylinders.

It is under the Centric Brand. They are about $33 plus shipping at rockauto.com.

Part number are:
14162066
14162065

AFCO has a brand new replacement brake calipers. They are about $49.99 plus shipping. $100 order are free shipping at Summit Racing, Jegs, and Speedway Motors. These should be NON low drag.

The part numbers are:
6635003
6635004
01-01-2015 05:58 PM
malibudave One of the main problems that arise when converting to manual brakes using a 7/8" bore master cylinder is LOW drag calipers.

LOW drag calipers require a step bore (quick take up) master cylinder. In my opinion they are too large to operate smaller 2.50" bore calipers with sufficient pressure, they are harder to bleed, and they have a 100lb residual valve that can fail. My opinion also is to change out to new (NOT rebuilt) calipers to make sure you do not get a set of LOW drag calipers.

To learn a little bit about new stock size calipers, I just purchased a set of left and right AFCO 2.5" bore metric calipers that are a bolt in, stock, replacement caliper for g-bodies, S10s, and most 3rd gen f-bodies. I removed the stainless steel piston and square piston seal to make sure it was not a LOW drag caliper.

SPECS:
MFG. Part #: 7241-9003 RH and 7241-9004 LH
Centerline of Holes: 5.50
Caliper Pistons: Single Piston Diameter: 2.50
Inlet fitting: 10mm-1.5 Material Type:
Steel Finish: Natural
Sold in Quantity: Each

Description:
The 2 1/2" bore steel GM metric caliper is designed to be a used as a stock replacement caliper. The caliper features a stock appearing remanufactured castings, remanufactured grounded 2 1/2" stainless steel piston, and low drag seals (see below) . Each caliper is assembled and pressure tested.

LOW DRAG SEALS
Though the description says "low drag seals", the seals are square with no noticable taper.




The seal-groove in the bore of the caliper are also square with no noticable taper.


When the seal is installed, it barely clears the top of the bore, and because of this, the piston to bore clearance, it seams, to have fairly tight tolerances.

The small end of the piston is what contacts the back of the brake pad. It measures 2.38".
The large end of the piston is what is inside the bore of the caliper. It measures 2.50"


Inside of piston cup, facing the brake pad.


Backside of piston that is installed inside the caliper bore.


I have bought these same exact part numbers a few years back and these new ones are a different casting with, what looks to be, a stainless steel piston. These calipers DO NOT come with pads, but they come with slider pins and slider pin bushings. At this time, they are around $40, and seem to be an improvement over the previous design.

Bottom line is that these should be a good stock replacement, NON low drag, brake caliper that will work with both strait bore master cylinders and step bore (quick take up) master cylinders.
06-21-2013 09:21 PM
malibudave Here is a list of strait bore master cylinders that will bolt up to a G-body’s angled firewall when using a flat, manual brake adapter plate. This is a list from smallest to largest.

21mm (0.826”) bore 1993 Dodge Shadow master cylinder (other years and models may work)
• Requires adapters to mate master cylinder outlet to stock lines. The adapter Part number is MC-SF at Disc Brake, Steering and Suspension Products for classic Chevy and Ford cars and trucks.
• Mounting holes spaced 3.25” versus GM master cylinder’s 3.375”.
• Hard to find.
• Light in weight.
• Advertised as 21mm, but may be delivered in 7/8” or 24mm bores. Measure bore size before you buy. Rebuilt/Used ones will have a “1” cast into the front of the aluminium body under the reservoir.
• Can buy new or used. New ones are fairly cheap to purchase.
• Aluminium body – new, used, or rebuilt.
• Large reservoir can hold enough fluid for rear disc brakes.

7/8” (0.875”) bore 1978-1980 GM G-body manual brake master cylinders.
• Can buy new or used. Rebuilt are fairly cheap. New are fairly expensive.
• Reservoir too small for rear disc brakes. The reservoir from 1979 Buick Riviera with four wheel disc brakes can be retrofitted to this master cylinder.
• Advertised as manual brake units, but may be delivered as a 24mm, vacuum power boosted unit. Measure bore size before you buy.
• Bolt in.
• Cast iron body – new, used, or rebuilt. (no aluminium)

7/8” (0.875”) bore 1993 Dodge Shadow master cylinder (other years and models may work)
• Requires adapters to mate master cylinder outlet to stock lines. The adapter Part number is MC-SF at Disc Brake, Steering and Suspension Products for classic Chevy and Ford cars and trucks.
• Mounting holes spaced 3.25” versus GM master cylinder’s 3.375”.
• Easier to find.
• Light in weight.
• Advertised as 7/8”, but may be delivered in a 24mm bore. Measure bore size before you buy.
• Rebuilt/Used ones will have an “8” cast into the front of the aluminium body under the reservoir.
• Can buy new or used. New ones are fairly cheap to purchase.
• Aluminium body – new, used, or rebuilt.
• Large reservoir can hold enough fluid for rear disc brakes.

24mm (0.944”) bore 1978-1980 GM G-body power brake master cylinders.
• Can buy new or used. Used are fairly cheap. New are fairly expensive.
• Reservoir too small for rear disc brakes. The reservoir from 1979 Buick Riviera with four wheel disc brakes can be retrofitted to this master cylinder.
• Bolt in.
• Come in cast iron and aluminium. 1978-1979 are cast iron. 1980 is aluminium (some models i.e. El Camino).
• New master cylinders will most likely be cast iron regardless of year.
• Rebuilt units come in cast iron and aluminium (1980 – some models).

24mm (0.944”) bore 1993 Dodge Shadow master cylinder (other years and models may work)
• Requires adapters to mate master cylinder outlet to stock lines. The adapter Part number is MC-SF at Disc Brake, Steering and Suspension Products for classic Chevy and Ford cars and trucks.
• Mounting holes spaced 3.25” versus GM master cylinder’s 3.375”.
• Easiest to find.
• Light in weight.
• Advertised as 24mm, but may be delivered in a 7/8” bore. Measure bore size before you buy.
• Rebuilt/Used ones will have a “4” cast into the front of the aluminium body under the reservoir.
• Can buy new or used. New ones are fairly cheap to purchase.
• Aluminium body – new, used, or rebuilt.
• Large reservoir can hold enough fluid for rear disc brakes.

24mm (0.944”) bore 1993 Dodge Dakota master cylinder (other years and models may work)
• Rear brake line outlet is 9/16-20 versus GM rear brake line fitting of 9/16-18. The fitting for GM brake line may be used to “rethread” the master cylinder’s outlet.
• Front brake lines bolt up.
• Mounting holes spaced 3.25” versus GM master cylinder’s 3.375”.
• Can buy new or used. New ones are fairly cheap to purchase.
• Aluminium body – new, used, or rebuilt.
• Large reservoir can hold enough fluid for rear disc brakes.
• Reservoir not angled like above Dodge and GM master cylinders.

1.0” bore 1979 Buick Riviera with 4 Wheel Disc Brakes.
• Can buy new or used. Used are fairly cheap. New are fairly expensive.
• Reservoir is made for rear disc brakes.
• Bolt in.
• Come in cast iron and aluminium.
• New master cylinders will most likely be cast iron.
• Rebuilt units usually come in aluminium.

1 1/32” (1.03”) bore 1985 Dodge Diplomat master cylinder (other years and models may work)
• Rear brake line outlet is 9/16-20 versus GM rear brake line fitting of 9/16-18. Fitting for GM brake line may be used to “rethread” the master cylinder’s outlet.
• Front brake lines bolt up.
• Mounting holes spaced 3.25” versus GM master cylinder’s 3.375”.
• Can buy new or used. New ones are fairly cheap to purchase.
• Aluminium body – new, used, or rebuilt.
• Large reservoir can hold enough fluid for rear disc brakes.
• Reservoir not angled like above Dodge and GM master cylinders.

1 1/8” (1.125”) bore 1985 Dodge Ram master cylinder (other years and models may work)• Rear brake line outlet is 9/16-20 versus GM rear brake line fitting of 9/16-18. Fitting for GM brake line may be used to “rethread” the master cylinder’s outlet.
• Front brake lines bolt up.
• Mounting holes spaced 3.25” versus GM master cylinder’s 3.375”.
• Can buy new or used. New ones are fairly cheap to purchase.
• Aluminium body – new, used, or rebuilt.
• Large reservoir can hold enough fluid for rear disc brakes.
• Reservoir not angled like above Dodge and GM master cylinders.
12-24-2012 05:14 PM
cobalt327 Glad to hear that you're stopping well again.

I have seen cases where, during the adjustment of the drums, the entire brake shoe assembly gets pushed to one side. This will give a "false" sensation of the shoes dragging slightly, making it seem that the shoes are adjusted w/a light brush w/the drum. But once the brakes are applied the shoes center themselves, and there's no dragging, or if there is still some drag, the shoes are still not out far enough.

I've gotten in the habit of taking the adjustment down far enough that the brakes are almost locked, then loosening them to the lightest drag setting.
12-24-2012 04:35 PM
S10xGN OMG!

You'll be happy to know the problem has been solved! There were (at least) two issues at work here:

1) After removing the rear drums (which I had so "carefully" adjusted) I found the PASS side to be spot on while the DR side had at least 3/8" clearance between the shoes and drum. This was causing a lot more master cylinder "stroke" to be absorbed by the rear circuit = increased pedal travel.

2) The bleeder screws were not at the highest point on the big-bore calipers, so I had them off the spindles and was using a 1" block of oak to simulate the rotor while bleeding them. What I wasn't seeing was that the oak block was actually deforming under the pressure. This time, after removing the air, I replaced the calipers on the spindles and finally had a good pedal. The car drives and stops better than before, so all is GREAT!

Russ
12-23-2012 10:32 AM
S10xGN
Quote:
Originally Posted by cobalt327 View Post
The combo valve need reset? Rear brake shoes adjusted to just barely brush drums?
No combi valve, since I am running "bigs and littles". If I can ever get the rear brakes to do their part, I may add a prop valve. I have manually adjusted the rear shoes until I can hear them scraping, yet 30# on my master will not actuate them at all? My next step will be to pull off the drums and watch the pistons under light pedal pressure. One thing I have noticed, the older drum vehicles usually have 1/4" line from the master to the rear TEE fitting and I used 3/16" all the way...

Russ
12-22-2012 04:52 PM
cobalt327
Quote:
Originally Posted by S10xGN View Post
Dave,

You say this works, Wilwood says it works... It doesn't work on my car. This is making me think there's a problem with the rear circuit. Even though I have had as much as 30 PSI on my pressure bleeder, the rear wheels would still turn by hand. I get good flow from both rear bleeders and these were new, complete drum kits from Ford. Maybe they were built wrong? I didn't spend any time looking at them, just slapped them on. Would defective rears give me an extended pedal stroke? Now I'm wondering if I should remove the drums and see what's happening on a pedal press?

Russ
The combo valve need reset? Rear brake shoes adjusted to just barely brush drums?
12-22-2012 09:58 AM
S10xGN Dave,

You say this works, Wilwood says it works... It doesn't work on my car. This is making me think there's a problem with the rear circuit. Even though I have had as much as 30 PSI on my pressure bleeder, the rear wheels would still turn by hand. I get good flow from both rear bleeders and these were new, complete drum kits from Ford. Maybe they were built wrong? I didn't spend any time looking at them, just slapped them on. Would defective rears give me an extended pedal stroke? Now I'm wondering if I should remove the drums and see what's happening on a pedal press?

Russ
12-20-2012 10:35 AM
S10xGN
Quote:
Originally Posted by malibudave View Post
Sorry to hear that. I have spent a B-load of money also to get to the point I am at. There is not reason that you should have gotten zero pressure when using a 1” bore master cylinder when I am getting pressure with a 24mm bore master cylinder using a 2.75” bore Wilwood calipers.

Things to try if you haven’t already:
1. How was the F100 brake lines mounted? Back brakes on the front port and Front Brakes on the back port (nearest to the firewall). How are yours usually mounted on the Maverick? I would think that you will need to match the brakes lines to what the f100 had, if the Maverick was not set up like the F100.

See pic below, this is the Grenada master but the F-100 is nearly identical. You can see the TEE to the front circuit under the blue 2# resid while the red 10# resid feeds the rear circuit.

2. If you didn’t bench bleed the master cylinder, take it off the firewall and bleed it on the bench to make sure you get a full piston stroke.

I always do this.

3. Make sure your bleeder screw, on the front calipers, is pointing strait up when mounted on the spindle to make sure all the air gets out. If not, remove from spindle, C-clamp the piston in the open position, clock the bleeder screw strait up, and then bleed that caliper.

With the Wilwoods, I had to do this. I used a 1" thick hardwood block in place of the rotor.

4. Make sure you’re your brake pedal is adjusted as far back toward the drivers seat as possible. Unscrew the brake light switch as far as you can with out it falling out easily, and then adjust the brake pedal pushrod out toward the piston of the master cylinder.

I made my pushrod adjustable, and the pedal is at the stock height.

5. Measure the piston stoke at the pushrod attachment point. I should have 7/8” to 1” of travel.

Hmmm, this I will take a look at. I can adjust it some, but really don't want my pedal a foot off the floor!

6. Make sure your brake pedal pushrod is just barely touching the back of the piston in the master cylinder. DO NOT PRELOAD the Master Cylinder piston.

The pushrod is clipped into a groove in the piston so it cannot come out. On the other end, the pedal has no stop so it can float freely.

7. The brake pedal pushrod should be inline with the master cylinders piston’s center line. If not inline, you will not the same pedal stroke and also wear out the master cylinder quicker.

Everything is comparable to stock as far as alignment goes.

My sister had a manual brake Maverick from the factory (25, or so, years ago). I cannot remember if it was front disc brakes or the year (I think 1976). But it had a very high pedal. I cannot remember how it stopped, but I know when the pedal released, it made a thud sound when returning to the depressed position.

Let me know what you find out.
12-19-2012 01:36 PM
malibudave Sorry to hear that. I have spent a B-load of money also to get to the point I am at. There is not reason that you should have gotten zero pressure when using a 1” bore master cylinder when I am getting pressure with a 24mm bore master cylinder using a 2.75” bore Wilwood calipers.

Things to try if you haven’t already:
1. How was the F100 brake lines mounted? Back brakes on the front port and Front Brakes on the back port (nearest to the firewall). How are yours usually mounted on the Maverick? I would think that you will need to match the brakes lines to what the f100 had, if the Maverick was not set up like the F100.
2. If you didn’t bench bleed the master cylinder, take it off the firewall and bleed it on the bench to make sure you get a full piston stroke.
3. Make sure your bleeder screw, on the front calipers, is pointing strait up when mounted on the spindle to make sure all the air gets out. If not, remove from spindle, C-clamp the piston in the open position, clock the bleeder screw strait up, and then bleed that caliper.
4. Make sure you’re your brake pedal is adjusted as far back toward the drivers seat as possible. Unscrew the brake light switch as far as you can with out it falling out easily, and then adjust the brake pedal pushrod out toward the piston of the master cylinder.
5. Measure the piston stoke at the pushrod attachment point. I should have 7/8” to 1” of travel.
6. Make sure your brake pedal pushrod is just barely touching the back of the piston in the master cylinder. DO NOT PRELOAD the Master Cylinder piston.
7. The brake pedal pushrod should be inline with the master cylinders piston’s center line. If not inline, you will not the same pedal stroke and also wear out the master cylinder quicker.

My sister had a manual brake Maverick from the factory (25, or so, years ago). I cannot remember if it was front disc brakes or the year (I think 1976). But it had a very high pedal. I cannot remember how it stopped, but I know when the pedal released, it made a thud sound when returning to the depressed position.

Let me know what you find out.
12-19-2012 10:11 AM
S10xGN Just to post back results, they were not good. The 1" bore master was still out of fluid at full stroke (pedal to the floor), even though a Wilwood tech assured me that 1" would supply plenty. In frustration, I swapped back to the original calipers, but did a full bleed after doing only one side. I had a pedal, but close to the floor. After swapping and bleeding both sides, I again had a good pedal. After all this d!cking around, the net change was from a 15/16" master to a 1" master, a lighter wallet, and a shelf full of wasted parts. I have not driven it yet, but I'm pretty sure the brakes will s%ck even worse than before...

Russ
11-26-2012 08:06 AM
S10xGN Well, so much for the C3 Corvette master, after "oblonging" the holes so it would fit my stud spacing, it wouldn't clear the valve cover. Had to order a 1970 F-100 master that more resembles my tall, upright Granada master but in 1" bore. Maybe by mid-week...

Russ
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