Early van brakes and service problems general. Although a lot of this article addresses disc brake issues, it also contains much information that pertains to any G van brake system.
Examples of disc brake brackets available for 2011, see the 7th post on this thread
Before you do anything else "READ THIS"
Disclaimer of Warranty:
Neither the seller, designer or manufacturer will be liable for any loss, damage or injury directly or indirectly arising from any use of this item. This bracket is not D.O.T. approved. Before using this product the user shall determine the suitability of this product for its intended use, and the installer shall assume 100% of all responsibility and liabilities, legal and financial, at all times and conditions under which it is used or misused. It is the responsibility of the installer and user to determine the compatibility of this product with the manufacture of any vehicle or other product said user intends to use in conjunction with this product. It is the responsibility of the installer and user of this product to know the laws governing the use of this product throughout the jurisdictional areas said user intends to use this product.
The following is not formal instruction or recommendation but simply a description of how I put these on my own van.
The first thing you need to understand is no two vans are exactly alike and your van may require some things be done differently then other vans. There are many Vanners on the web sites willing to answer your questions and assist you as best they can. Ultimately you are doing the job and will have to deal with what differences come up on your van. Changing your van to disc brakes is absolutely not a one size fits all, out of the box bolt on kit.
Here is what I did on my van.
I put my machine on safety stands and pulled off both front drums, then the hubs, then I disconnected the front flex hoses at the frame attach point by cutting the steel line and the clip. Removed the four bolts holding the backing plates onto the spindles without taking any of the other brake parts off the backing plate. I had to shove the brake shoes aft a bit to get the bottom bolt out but it all came off as one piece quick and easy.
I actually replaced all the steel lines on my van because old brake fluid gets corrosive. It doesn't really flow much while being used and rusts brake lines on the inside. Sometimes this clogs the line restricting flow causing uneven braking during emergency stopping or dragging brakes. Other times a line could be about to blow; which will show up when under emergency braking right when you didn't need to find that out. Any brake lines more then 20 years old should not be trusted as safe. I replaced all my lines, hoses and fluid, it was the smartest $50 ever spent. Use 3/16 seem less galvanized or stainless steel lines.
I cleaned up all rust and scale from the spindle mounting surfaces and gave them the paint they deserve.
I installed the brackets on the outside of the spindles with the offset to the inside and to position the calipers forward. I used three new bolts per side. One 2+ ¾" 7/16NF grade 8 or better with self locking nut and two 1+ 5/8" 7/16 NF grade 8 with self locking nuts. At this part I would never use bolts less then grade 8, Because I don’t want to die. I replaced the fourth castellated nut with a new self locking nut. Grade 8 bolts will have five dashes on the head. I provided army-navy military spec part numbers for these bolts so anyone with access to the Services or a civilian aircraft repair facility can get high quality stuff there.
I Use the rear brake rotor from a 1979-81 Trans-Am. I picked up two at NAPA # 85774. This same rotor comes made in America or made overseas or in the drilled high performance version all at different prices.
HUB PREPERATION:
The hub preparation is probably the most important part of this installation.
The rotor did not fit both of my hubs the same, or strait, because of un-machined, out of round casting, slag and a ridge on the barrel of one of my hubs.
Hat type rotors have to fit nice and easily onto a clean, flush and strait mounting.
This size rotor must have not more then .004” run out or they may pulsate and cause a lower pedal. In fact all current day manufacturers require the wheel nuts to be torque evenly because this fit is that sensitive that unevenly tightened wheel nuts will cause brake pulsation. Wheel nut torque should be a star pattern at about 45 then 90 ft/lbs on 7/16 studs.
Studs
I removed the studs for ease of clean up and filing before replacing them with ½" longer ones. The rotor is 3/16" thicker then the drums, this will cause that much less wheel stud protrusion. If I were mounting steel wheels this might not be a problem but I am installing much thicker Magnesium wheels and decided the original studs were not long enough. There should be a min of 9 turns engagement on the wheel nuts.
I used NAPA # 641-1267 studs.
The studs can be just pound out with a 2lb Hammer. Some people prefer to use a press.
Please NOTE: These instructions are for the G series vans... If you have any experience with installing disc brakes in the A or E series vans, your input would be appreciated!
The hubs remounted onto the spindles can be held and rotated easily while filing.
Look at the ingenious set up Kakster created!
I put my hubs on a lathe to clean them up. But I used the lathe only to spin to hubs, I did not machine them on the lathe, Like KaKster I used a file and emery cloth to mill them down to correct size. I did this because the circular areas that need to be reduced must stay true with the bearing surfaces inside the hub and the hub could not be mounted onto the lathe 100% true. If I had used the lathe tools to “Cut” the spindle it would have made the rotor run off center. A file and emery cloth ride the hub evenly all around even if it feels a little off center.
I had to remove high spots from the outer diameter and radius the corner so the hub would fit well in the rotor.
The rotor MUST fit over the hub freely !
This ridge has to be filed down to “just fit” the inner rotor centering hole snug. This is what makes the rotor centered on the hub.
I removed this evenly all the way around while spinning the hub.
There is the ridge trimmed down. Filing 101
You can also see in this picture the nice radius I put on the outer diameter so it fit inside the rotor real clean.
On one of my hubs the casting on the back rubbed on the bracket around the inside. This was a file fit as well.
I also filed the face of the hub, you can see where there was a high spot from previous stud damage.
The new studs can be drawn in using a standard wheel nut (reversed) and a spacer or stack of washers. I zap them in with a impact wrench. This pulls the stud spline in strait to its bottom. Using a hammer to install the studs may distort the hub face. Sometimes a hydraulic press can be used to install the studs, care must be taken to support the hub immediately around the stud when using a press so the hub face does not become distorted like that previous damage in the above picture.
After checking final fit into the rotor hat.
A little paint, repack the bearings, new grease seals and install. I used new dust caps too.
Install the rotor, this is the time to check for run out.
An explanation of how to check and correct your rotor run out can be found in the Early van brakes and service problems article found on the home pages of
VCVC.org or Vintage- vans.com
These shims are available to correct .003”, .006” and .009” at parts jobber stores. UAP NAPA part number is BA80303, BA 80306 and BA80309 respectively.
The hat type rotor can also have run out and knock back caused by loose or worn wheel bearings just like the solid rotor mention above.
I used a dial indicator on the installed rotor to measure and correct its run out. This should be done at initial installation and then will only need rechecking if a brake pulsation occurs.
Pad installation
Hold the rotor in position with nuts and install pads and calipers
Note: the outside pad needs to be crimped so it fits the caliper tight and I recommend using "break quiet" .
Use standard brake pads only they will give you best braking performance for this application. High performance, High heat or Racing brake pads will give you poor street braking performance! They don’t bite until they are up to 4000* and higher.
This top tab is made to be dent down just enough to make the pad fit tight onto the caliper
If the tab is bent just right the outer pad should have to be pinched on using channel lock pliers or "C" clamp. But wont take much force at all to install. Its just a “Rub tight ” fit.
Install the hoses
Flex hoses are another story. There can be many options depending on the high of your suspension and where on the frame you want to attach them. You want the hose to be as small in diameter and as short as possible but have enough length to handle full turning left to right at "fully extended suspension high”. The hose will be long when suspension is compressed. You must make observations of the hoses behavior and take measures to prevent it from getting caught in the rotating wheel or getting hooked on any stationary component. I clamped my hoses low on the shock body in such a way that lower section of hose below the clamp deals with the steering left to right and the upper portion of the hose deals with the suspension travel up and down. The clamp on the shock is low enough that when the shock is fully compressed the top bell on the shock does not hit the clamp.
PARTS LIST, “Napa numbers”
Rotors; # 48-85774 1979 – 81 Trans-am (four wheel disc) rear rotor.
Pads # AE728A Basic # 728 pads used on lots of GMs
Calipers #
SDC2422028 and SDC 2422029 79-81 Trans –Am front.
SDC2422028 and SDC 2422029 79-81 Trans –Am front.Hoses # 38102 (19”) or (for lower ride height 36845 (15”))
Banjo Bolts # 82703
Long Wheel studs # 641-1267
4 Grade 8 bolts 7/16 20 NF X 1+ 5/8" or (mil spec) AN7-15A
2 grade 8 bolts 7/16 20 NF X 2+ ¾" or (mil spec) AN7-26A
8 lock nuts 7/16 20 NF
If needed
Grease seals # 17187
Outer bearings # BR2
Inner bearings # BR6
Dust Caps #730-2436
Other mods that I needed to do
Unlike the 2nd Gen, the 1st Gen sway bar has to be lowered at its frame mounting using 2" blocks and longer bolts to clear a duel master cylinder. The belly pan needs to be trimmed to accommodate this.
1st Gen Sway bar Mods:
Frame bushings 1st Gen NAPA PN 265-1925
End link kits 1st Gen NAPA PN 18070
Additional notes for disc brake installation:
Some little know reasons for spongy or less then solid brake pedal.
Aside from the usual air in the system or master cylinder not properly bench bleed.
Drum brakes although self adjusting should have the adjuster checked for freedom of movement and be periodically manually adjusted.
Calipers that hang up on the caliper bracket will cause much pedal loss.
I had to file the flats a little where the calipers make contact.
Read more at this link.
But that statement is not enough!! The caliper needs to be absolutely free to slide on the guide pins when installed. You should observe the caliper moving when your friend presses hard on the pedal. YOU SHOULD NOT SEE ANY FLEXING OF THE CALLIPER BRACKET!! If the bracket is flexing at all (look carefully) the caliper is hanging up. This will happen when any one of the two slide pins (when installed tight) pull or push the caliper hard up against either slide flat. I have mentioned earlier the brackets might be tight and I had to file the flats but I discovered that the initial file fit must also include installing one guide pin and check to see the caliper is free on both flats when the other guide pin holes line up. Better yet you should be able to move the unbolted end of the caliper up and down to intentionally misalign the holes about a 1/16" and observe the caliper not binding at either flat. Now remove that first slide pin and install the other by itself in the other hole and look for the same results. One of my brackets would fit the caliper nice but then lock up on one flat when the pins were installed. This made the bracket flex inboard when the brakes were applied. The bracket would flex about 1/16", enough to see by eye, and that caused about ½" of pedal loss.
Loose wheel bearings will also cause a lower then normal or spongy pedal.
Another thing that causes pedal loss or sponginess is flex hoses with a twist on them when mounted. The hose will try to straighten itself out under pressure resulting in some pedal loss. You might notice the new hose has all the numbers and a strait line printed on it. That line should be strait when installed, not spiraling around at all if possible.
It is recommended to use the smallest brake lines you can get away with. Usually 3/16 line is best.
We should add, the installation I did which you read here was on a 65.
The 2nd gen vans have the flex hoses attach to the frame forward of the wheel were the 1st gen attaches behind. Also the 2nd gen sway bar is quite different and may require some alteration at the axle mounting. Some people have installed these brackets on the 2nd gen and reported they did not have to make any changes to the sway bar brackets.
-again because each van and parts they are made up from
is different, some alterations may be needed for your situation.
Brake Boosters and power brakes. A separate topic which requires much modification and fabrication skills. Has been done in several different ways, there is no one best way. You will have to do much research if you want power brakes.
Brake Pedal Height adjustment, see the link on Early van brakes and service problems general . (at the beginning of this article)
The master cylinder
Many people have changed their master out several times trying to get the pedal feel they want, including me.
They have tried the 2nd gen master, 3rd gen master, early corvette, 79-80 firebird, F150, and others. Most of these should work with varying degrees of success, or not. The corvette style master ( in two sizes) is what most aftermarket brake kit suppliers sell.
I am reluctant to state what I think is best because so many Vanners install a master and then get all hot under the collar because their van brakes don't feel like their 2009 Escalade brakes or what ever they were expecting it to feel like. They come back at me as if its my fault that they had unrealistic expectations.
The crazy part is, in most of those cases they didn't have the brakes at the wheels installed right or bleed right and their problem had nothing to do with the master which they didn't discover until they went to a 2nd or 3rd master type.
Here are the basic requirements to be considered.
#1 Need to know if and what residual check valves are inside a master. Masters came with all kinds of arrangements of built in residual check valves depending on what vehicle they where made for. Unfortunately the only way I know of being sure is to know what the brakes will act like if you have the residual valves wrong. So I choose a master cylinder that has none, and I added then to the outside.
Most all aftermarket brake kit suppliers, like the early corvette master because its low profile, comes in two bore sizes, has standard bolt and line sizes, and has no internal residual check valves. I used one of these because it fits all the needs of my van.
#2 master cylinders can come in many different Bore sizes and also in the "quick take up" type with stepped bore. Basically for these vans and every other vehicle in this weight class using these calipers and rotors either the 1" or 1.125" bore works . This is where personal preference of 'feel" comes in, and one has to make a choice. Because the original van brake pedal arm is not the best geometric ratio for either power or manual brakes, you get to play with choosing what you personally prefer.
The other reality about choosing a bore size is what do you have at the wheels?? drum/drum? disc/drum? disc/disc? or more to the point what size pistons are in the calipers and cylinders(how much fluid volume do they consume??).
Its a mater of physics, regardless of what’s at the wheels, a 1" bore master will give a lower pedal but be easier to push. A larger 1.125" bore will give a higher pedal but be harder to apply the same amount of braking force.
Some vanners are happy with the 1" on their set up.
I have chosen the 1.125" bore for my van.
Note: parts counter people may try to tell you Bore size is related to "power or manual" brakes but that’s not so. They deduce that based on the what they see on their application listings.
#3 is the question of power master vs manual master. There is only one difference between a power vs manual master and that is the hole depth in the piston where the pedal rod inserts. Power brake masters have a shallow hole because they are attached to a booster where the rod is not going to fall out of the master. Manual masters have a deeper hole in the piston so when you let you foot off the pedal and the pedal spring up faster then the master's piston returns, the rod will not fall out of the master. (Which would be bad on next brake application).
So to recap. You want a manual (deep hole) master.
you want a master with no internal residual valves.
you have to choose if 1" or 1.125" bore is what you like.
Look here
I am using the 1.125" bore deep hole master from “Tuff stuff “ , included was a bullet insert to convert the same master to a shallow hole, which I am using now because I switched up to a power booster. And I have changed up the pedal geometry to increase pedal height. This all very different then the early corvette application which used a 1" bore master for four wheel manual disc set up, but that car had a very different pedal linkage geometry.
Look under "universal MASTERS" PLAIN, 1.125".
Or Napa # M1974
Our vans need residual valves for each circuit whether it’s a disc/disc or disc/drum or drum/drum set up. Street rods and vehicles like our vans which have the master at or close to the same level as the calipers will gravity feed the fluid back to and overflow the master (a sure sign of this is always having to pump the brake once even though there is no air in the system). This can be prevented with the use of a single 10lb residual valve on the drum brake line and especially a single 2 lb residual valve on the disc brake line mount just out side the master cylinder. Residual valves will also attribute to a better brake pedal feel.They are available from aftermarket suppliers.
It is very important to not have more then one external valve on any circuit or you may have brakes that don't release or drag or can’t be bleed. I use the four disc master because it has no internal valves and I use two 2lb external valves on my van.
The rear brake line always connects to the pushrod end of the master cylinder so the rear brakes will begin to apply first.
Proportioning valves do not change the pressure to the rear wheels, what they do is slow the rate at which the rear brakes get up to the pressure the front have. Eventually all wheels will have the same pressure. Proportioning is actually a function of the wheel cylinder size and/or caliper piston size. (But can also be effected by many other factors like tire size, weight distribution rate of braking, tire pressures and so on) For these and many other factors proportioning valve are designed very vehicle specific. Any car model will have different proportioning valves depending on which engine the have, what accessories and so on. Vehicle designers and racers know that there is no way there can be a “universal” proportioning valve that works right on any vehicle.
That is why there is the “Adjustable Proportioning Valve”
I use a manually adjustable proportioning valve. These valves come with easy instructions for setting. Generally they should be initially set around mid adjustment, then very carefully try braking at slow speeds and work your way up to higher speeds in a safe environment. Try gentle braking at first and work your way to a full blown panic stop. Adjust the proportioning valve as required to attain all round best braking. Each and every vehicle will have its own best adjustment. And if you change you van, the tire size or load it up with weight or tow a trailer you can adjust for the changes real easy.
I had installed my valve with the knob at the master cylinder access hole so I can adjust it through the hole and then cover it so it doesn't get accidentally changed. Now I have it in the dog house where I can also easily reach it.
M1DADIO
