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  #16 (permalink)  
Old 07-29-2012, 03:49 PM
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  #17 (permalink)  
Old 07-29-2012, 03:50 PM
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Old 07-29-2012, 03:50 PM
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I purchased my second new master cylinder from rockauto.com a while back and just now had time to install it. The master cylinder is a Centric brand PN# 130.62005. It is a manual brake master cylinder for a g-body with a 7/8" bore. I installed it and bleed the brakes from back to front and got a good, firm pedal. I left the speedway motors recalled calipers installed, for now, to see how the system all worked together. I noticed, while I was under the car bleeding the brakes, I saw a lot of caliper defection as my dad pumped the brake pedal when the bleeder screws where closed.

How did it do? For the setup I have, it did very well. I could not lock up the front brakes, but the braking felt more confident than when I had the stock, 24mm bore power master cylinder . I felt, if I was driving this on the street a lot, I wouldn't have to anticipate my braking. I felt I could stop where I wanted to when I wanted to under normal street driving. As expected, the pedal stroke is longer than a power brake pedal.

What would I do different? I would find a better front caliper. I think I will try the Wilwood single piston, 2.75" bore, metric caliper. From my experience with the inspection of 2" bore, Wilwood, single piston, metric calipers, I think the 2.75" big bore Wilwood will have a larger piston that the CCP/Speedway Motors 2.75" big bore caliper. I just worry that any 7/8" bore master cylinder may not have the volume of brake fluid needed to make these work.
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Old 07-29-2012, 03:51 PM
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Things I learned from this process.

*New master cylinders are hit or miss in functionality. My first new one I bought did not work, but it was a clearance item from rockauto.com. I ended up spending another $80 plus shipping for the Centric brand one that actually worked.
*The larger the caliper piston is the better the clamping force.
*Caliper deflection affects brake performance more that I thought.
*The smaller the bore of the master cylinder is the better the pressure to the caliper.
*But if the bore of the master cylinder is to small, it may not have enough fluid to fully compress the caliper piston.
*The diameter of the brake rotor also affects the performace of the brakes not only because of rotor area and heat dissipaton, but also a larger diameter rotor gives the brakes greater leverage. Just think of using a 6" long breaker bar instead of a 5.25" braker bar to get a bolt loose. A longer bar will have a easier time getting the bolt loose. A 10.5" rotor has a 5.25" (half the rotor diameter) of "leverage". A 12" rotor has 6" of "leverage". Larger is better.
*They make brake pad designed for drag racers. They work better when cold and are for vehicles that do not use their brakes on a daily basis.
*Wilwood makes nice metric calipers.
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Old 08-07-2012, 10:05 PM
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Just recieved my Wilwood 2.75" big bore calipers in today. These are very nice calipers, just like the Wilwood 2 inch metric calipers. The piston diameter measures 2.704 inches. On the underside of the caliper, there are ridges that bridge the piston side (inside) of the caliper to the wheel side (outside) of the caliper. These ridges are not present on any of the other calipers. These ridges should cut down of caliper deflection. The weight of each of the 2.75" calipers is 4 lbs 8.6 ounces with out the bleeder screw. I hope the 7/8" bore g-body manual brake master cylinder can handle the increase in volume these calipers may require.





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Old 08-07-2012, 10:06 PM
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Caliper Specs

Caliper............................Part Number........Advertised Bore Size.......Actual Piston Size.....Weight
Wilwood 2" Bore Caliper........PN 120-9333...................2.00"...................... ....1.981"................4lb 1.6oz
US Brake / AFCO Caliper.......PN 7241-9004..................2.50"....................... ...2.376"................6lb 4.7oz
CCP Big Bore Caliper............PN CP412526...................2.75".................. .........2.565"................6lb 11.2oz
Wilwood 2.75" Bore Caliper....PN 120-8926...................2.75"...................... .....2.704"................4lb 8.6oz
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Old 08-15-2012, 06:47 PM
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G-bodys came with manual brakes from factory, I had a 80 malibu 4 dr., 3 on the floor and id stopped mint, i liked it better than power brakes. When I parted out the car I kept the master and put it on my El Camino that had power brakes, all i did was switch masters and used the pushrod from the manual setup, case closed, worked perfect. When you start changing front calipers to bigger bores you need more fluid, and than you mess up all the engineering work GM did, lol. I have g-body calipers on my 50 chevy and my 57 pontiac, I bet they are heavier than any g-body, and have never had a problem.

Last edited by krazeyone; 08-15-2012 at 06:52 PM. Reason: forgot something
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Old 08-16-2012, 08:02 AM
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Krazeyone, thanks for the feedback. Good thing is that almost all g-body cars from 1978 to 1988 are set up from the factory to accept manual brakes. The hole is drilled in the pedal, so all you need is a plate to cover the firewall, an adjustable pushrod, and a retention cup to keep it from falling out the back of G-body 7/8” bore manual brake master cylinder. Problem is now most rebuilt calipers may be of the quick take up (low drag) variety and are problematic (won’t have the volume) when using a strait bore master like the 7/8” bore g-body master cylinder. A step bore master cylinder is required for those brakes and, in my opinion, have to large of a bore at 24mm. I assume your calipers on your 50 and 57 were part of a kit, so they, more than likely, would not be quick take up (low drag). But if you bought them at the auto parts store, they may be the low drag type, because these calipers where used from 1978 to 2003 on G-bodies, 3rd gen F-bodies, and S-10 Trucks and SUVs. Most of these cars from 1981 on came with the quick take up (low drag) calipers. Do the auto part store’s suppliers rebuild them with out the quick take up design? I have not idea, so that is why I would always go aftermarket when using a metric caliper.

I believe the problem I have now is caliper deflection and or a pad that requires more heat (FF rated) to work. The bore size of the caliper is only an issue if the MC doesn’t have the fluid volume to make it work. With an increase in bore size and piston area, I should see an increase in clamping force. I am going to try the 2.75” big bore Wilwood metric calipers and test to see if my 7/8” bore master has the volume. If it does, and I don’t get the braking I want, I will then change to a different (EE rated) pad.

David Schultz
manualbrakes.com
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Old 08-27-2012, 10:29 AM
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This week I put on the Wilwood big bore calipers. I got them bled and immediately had less pedal pressure when using the 7/8” G-Body manual brake master cylinder. The pedal almost went to the floor. I assume it is from the increased piston diameter over the Speedwaymotors.com “Big Bore” calipers (2.704” Wilwood v 2.565” Speedwaymotors/CCP) that I replaced. When driving with the Wilwood big bore calipers, I could pump the pedal 3 or 4 times and get the pressure I needed and would lock up the right rear tire and stop the car just like the other calipers. I suspect now I will need a 24mm bore G-body master cylinder (from a power, vacuum boosted G-body) and EE rated front pads to replace the FF rated front pads I have on the front now. The EE rated front pads have better “bite” when the rotor is colder. FF rated front pads have better “bite” when the rotor heats up. Since this is a street driven car, the EE rated pads should be a better choice and will match the rear EE rated shoes that are already on the car.
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Old 11-21-2012, 04:25 PM
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I am done testing the manual brake setup with a stock, aluminum, rebuilt, 24mm bore, 1980 El Camino master cylinder. With only this change, I got back the brake fluid pressure that I lost when I upgraded to the Wilwood 2.75” metric calipers using the 7/8” bore master cylinder. I bench bleed the master cylinder installed it in place of the 7/8” bore master cylinder, bled the line at the master cylinder, and then bled the car at all four wheels.

On the test drive, using the 24mm master, I did a few hard stops from about 30 mph. I was rewarded with both rear wheels locking up, but the front braking system felt as if it still wasn’t grabbing. After the testing, I jacked the front of the car and removed the wheels and I unbolted the calipers so I can take a look at the pads. I suppose during my very first manual brake test, I did not bed the brakes in properly and I glazed the brake pads over. I do not know why I did not notice this when I put on the Wilwood calipers other than not recognizing what glazed pads look like. The glazing most likely happened because I had a large master cylinder and small calipers on my first manual brake test and, at the time, I wasn’t getting enough pressure to the pads to do accomplish correct bedding. The moral of the story is to bed your pads properly.

Good news is that I found out what the issue is with the front brakes not grabbing. Bad news is that I didn’t deglaze my pads and retest. I didn’t deglaze the pads I originally used because went ahead and upgraded to a Wilwood Polymatrix A brake pad.

I went to the Wilwood PolymatrixA pad because of its good, cold clamping properties and, before I realized about the glazing pads, I had thought this would help with front brakes. **As a warning from Wilwood to any one using these pads, Wilwood considers these race pads**. These are aggressive pads and will most likely wear the front rotors prematurely and are intended for race use only. These pads have almost twice the friction coefficient as a “stock” type pad. I am using this aggressive pad because the front rotors are small, the brake pads are small, the front calipers are a floating design, and the car is now has manual brakes. These pads are also a wallet buster at $150 a set.

The braking test with these pads where a noticeable night a day difference. I felt very comfortable and confident while driving and stopping. On hard stops, the nose of the car would “dive” down and the rear wheels still locked up. Only time will tell if these front pads are good for everyday use with this manual brake setup.

If your car is a daily driver and not a drag car, you most likely do not need to change out to larger wheel cylinders on the rear drum brakes like I did. The original stock 3/4” bore wheel cylinders versus the larger 7/8” bore wheel cylinders should reduce rear lock up on hard braking.

For a drag racer with large, wide, sticky tires on the back, the larger 7/8” bore wheel cylinder may be better to keep the rear tires from spinning when your holding the car on the line with just the brakes. An aggressive front pad may also be needed to hold the car on the line (contact one of the major brake pad manufactures for suggestions).

From my experience, to do a manual brake system on a g-body or s-10, some or all of the brake components will have to be replaced. You cannot just remove the vacuum booster and bolt the master cylinder to the firewall and expect your braking to function well. It is a system approach.

Do you need an oversized caliper? In my opinion, no you do not.

Do you need to change out the front calipers? In my opinion, yes you do. Why? Because the stock calipers may or may not be a LOW DRAG design which requires a step bore master cylinder. How do you know that you have LOW DRAG calipers? You actually cannot physically tell, so its best to buy aftermarket calipers to cut down on variables that may cause trouble with your braking system.

Do I recommend rebuilt front calipers from the auto parts store? No. See above.

Do you need to change out the master cylinder? In my opinion, most likely you will need to. Why? It depends on what you are starting with. If you have a GM g-body vehicle that was built from 1978 to 1980, you have a strait bore, 24mm bore master cylinder from the factory and you can just upgrade to Wilwood 2.75” bore calipers if you master cylinder is in good working order. If you have a vehicle built from 1981 through 2003 you most likely have a step bore master cylinder. These master cylinders are too large for almost all manual brake conversions on a g-body or s-10. Now a choice has to be made. How much money do you want to spend on aftermarket front calipers? Cheapest ones that I have found are around $45 each with a stock size bore from U.S. Brakes. You will then need a 7/8” bore master cylinder to match to these front calipers. For a g-body car you can go with a new or rebuilt, stock replacement from a 1978 to 1980 g-body manual brake master cylinder. For an S-10, the only option I have found that readily bolts to the firewall and to the brake lines is a Wilwood 7/8” bore master cylinder. If upgrading to the Wilwood 2.75” bore calipers, you will need a 24mm master cylinder. The g-body options are a new or built stock power brake unit from a 1978 to 1980 g-body car. New ones will be cast iron. Most rebuilt ones will be cast iron. For some reason, the 1980 model years came in aluminum and these can be bought rebuilt (like I have installed in the latest test). For a s-10, you can use a stock replacement manual brake master cylinder from a 1982 to 1992 s-10 truck with manual brakes. These are step bore master cylinders with a primary bore of 1-1/4” and a secondary bore of 24mm. I do not recommend these master cylinders because they are hard to bleed and have a bypass valve that can fail. The other options are a 24mm Wilwood master cylinder and a 1990s 24mm Dodge Dakota master cylinder. Only issue with the Dakota master is the rear brake port is 9/16-20 instead of 9/16-18. I have found no adapter for this conversion yet.

Do I recommend step bore master cylinders? No, because they are generally too large for a stock size front caliper, they are hard to bleed, and they have a bypass valve that may fail. These three issues can be remedied by using a correct size strait bore master cylinder. A 7/8” bore master cylinder for stock bore, aftermarket calipers and 24mm bore master cylinder for a Wilwood 2.75” bore calipers.

Do I recommend other oversized front calipers other than the Wilwood 2.75” front calipers? No, because their piston size in these oversized calipers are not much larger than stock. The Wilwood caliper, visually, looks to be engineered better.

Do I recommend stock size calipers? U.S. Brake is the only caliper, of the aftermarket cast iron replacements I know, that is not a low drag caliper. There may be other aftermarket, “metric” calipers, but I cannot confirm if they are low drag or not. The U.S. Brake calipers are based on a stock casting. The other alternative is a stock, replacement aluminum, “metric” caliper from Wilwood. I have not used or viewed one of these calipers, but from engineering of the 2.75” bore and 2.00” bore calipers I have viewed, I suspect they should be just as well engineered and lighter.

Do I recommend larger wheel cylinders? If the car is street driven, most likely no. If drag raced, most likely yes to keep the rear tires from spinning when doing a brake stand

Do I recommend braided stainless steel flex lines? Yes, for the reduced ballooning and better pedal feel, but is not necessary.
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  #26 (permalink)  
Old 11-22-2012, 09:57 AM
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Strange that I missed this thread before. I'm going through something similar with my Maverick. I have (had?) factory "GM Metric" front calipers and Ford Racing 11 x 2 1/4" drums in the rear with a 15/16" bore Grenada master. Car always had a high hard pedal but very poor stopping, which made me leery of driving it. In search of some actual "braking", I swapped out to the Wilwood 2.75" bore calipers and now my pedal goes straight to the floor, out of fluid. I can get a pedal by pumping it several times, but that won't cut it on the street. Just ordered a 1" bore master and will see how much pedal I will get. BTW, that caliper change is a 34% increase in piston area per side!

Russ
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Old 11-22-2012, 05:32 PM
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I do have a long pedal travel, but the brake "feel" starts about a fourth of the way down and full lock up, of the rear wheels, happens about 3/4th, or a little more, of the way down. I may be at the very limit of this 24mn bore master cylinder.

Though the 24mm bore MC is just a tad larger than the 15/16" bore. It might be just enough to run out of fluid.

Let me know how the 1" bore MC works with your setup.
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Old 11-26-2012, 08:06 AM
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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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Old 12-19-2012, 10:11 AM
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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
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Old 12-19-2012, 01:36 PM
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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.
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