M1D disc brake, 3 technical updates july 2014

If you have or are going to have front disc brakes this info will be usefull to you.

http://www.vcvc.org/showthread.php/25039-M1D-Disc-brake-technical-update-July-2014-1-Pad-fit


Sorry; Too lazy to re-create all this info

M1D

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,,,,,you know nobody here can read these unless they have a VCVC password.....

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Which set up did you put on it,,,,,,

I used the same front disc flex line for my 2nd gen as I used on the 1st gen. Part number BH38102 for both sides.
I like the fit.

1st gen




2nd gen




some of you may notice I have the flex line attached to the frame bracket in the opposite direction the original drum flex hose was. I do this for two reasons, #1 the part of the hose that moves up and down with suspension travel is well protected from the tire and wheel being behind the shock. #2 and more importantly this reduces the length of the front brake lines by about 12" on each side. (The less line the better).

On a side note; the sway bar bushings for the second gen are larger then the first gen. the part number for the bushing and the link I have listed on my instruction sheet is for a 1st gen.
I reused the old 2nd gen sway bar link because it is a good length for this install and I replaced the rubbers with new.

M1D Disc brake Technical update #2 July 2014
I installed a factory sway bar on my 2nd gen and encountered interference with my disc caliper which is what some other vanners have also reported. I corrected the problem quite easily in a manner previously mentioned, today I have some pictures on how to deal with this.
Be aware that your caliper will move inboard as your pads ware down so you should have at least a 1/4" of clearance from new.
The problem is the banjo bolt at the flex hose to caliper attachment hits the lower sway bar bracket on full turns.

There has been other remedies but this one is the easiest.

First you need to switch the brackets to opposite sides of the van, This will make the sway bar link be further back overtop the axle. Also cut a healthy 1/2" out of the vertical portion of the bracket on the caliper side.




This will make for ample clearance as seen here on this newly installed disc set up, shown at full turn.

It seems some brake pads are being manufactured with different backing plates these days. I am the 3rd person to run into this issue this year. The brakes pads used to all have a specific shaped steel back plate except for the "heavy service pads" (sometimes called Police pads).
I don't know if its different brands or grade or quality of disc pad but some have extra steel that has to be ground off so they will fit into the M1D80TA bracket properly. The extra steel in the lower corners makes the pad sit on an angle which is not good. This problem is on the inside pad only.
The older style and some still available today had minimal steel in the lower corner.




The new pads I bought last month seen below are supposed to be the replacement for the original pad.

I had t o grind this extra metal off the corner to make them fit flat.




This provides clearance right at the bend in the bracket

Tech update #4 2nd gen master cylinder.
So now that I have a 2nd gen to do these mods to, I am discovering problems and having a change of opinion on some items.

I installed the low profile aftermarket master cylinder in the 68 G10 today and found four reasons why the 2nd gen master should be consider a good choice.

#1; I had to cut open the mounting bracket wider to fit the new master.
#2; I had to temporarily drop the sway bar and lower the rad a bit to fit the new master into place.
#3: The park brake cable rubs on the side of the master cylinder.
#4: The throttle rod rubs and jams on the top lid of the new master cylinder.

In many cases people are changing their park brake set up and throttle linkage set up all at the same time anyway so to that extent I would still recommend the Corvette style master cylinder.

However: if you are not changing those fore mentioned items and are doing a disc conversion only; you might consider staying with the 2nd gen master cylinder to avoid all that extra work. But if you are staying with the 2nd gen master!!
Oh wait! I now have a 2nd gen master and decided to see for myself. Well look here, just like it states in the data and rebuild kit. It has built in 10lb residual check valves!!!
(not good for disc brakes)

That little top hat thingy with the spring is a 10lb residual check valve. You need residual check valves but you need a 2lb for disc brakes and a 10lb for drum brakes.

You have to pull out the brass furl insert to remove that valve and reinstall the furl if you haven’t destroyed it getting it out. you can see in the previous photo a drove a screw into is and pulled it out of its press fit with vise grips.


Alternatively you could test your master with a gauge but it might be led work just to take it apart , or go to a different master.
I recommend as a minimum; you temporarily install a low pressure gauge (say 0 to 100) onto the master’s outlets one at a time and depress the master only enough to go higher than 40 PSi and not exceed the limit of the gauge or you will destroy it. Then release the pedal and make sure it returns to "0" PSi. and not stay at 10 psi. That will confirm no built in residual drum brake valves and you’re good to go. (Some have the valves, some do not) You will still require other valving as applicable to your conversion.

I still recommend the corvette style master;
#1 If you are doing a first gen you have to cut the bracket anyway and the park brake cable and throttle rod do not interfere.
#2 if you are doing a second gen and changing the throttle linkage to a cable and changing the park brake system to modern "sheathed Cables”.

If you have bought yourself one master cylinder and have not installed it yet, you can always return it saying you ordered the wrong one.

Had to cut open the mounting bracket



The park brake cable drags on the master



The throttle rod rubs and jams on the top

On another note: here is a little feature that comes with the aftermarket master cylinders so the same master can be used as "manual" or "Power" brake.. Note the only difference between a manual or power master is the depth of the push rod hole, all else is the same.

The deep hole is for manual brakes.



the aftermarket master comes with a "Bullet" to convert the master to a short hole for power applications




It is extremely important not to use a short hole master cylinder when running a manual brake set up. The pushrod could fall out causing total brake system failure.

You do not need to modify the 1st or 2nd gen push rod when going manual brake cylinder.

If you put the wrong master onto a power booster you will never get a pedal and possibly destroy the booster.

Some more info on master cylinders and lines.

On bench bleading a master cylinder:

many people believe they can do the "Bench blead" of the master cylinder after its installed.
Well you can if you know what to look for and how to do it. The main thing is the master cylinder must first be level or it will trap air in the high end.

just like you see here

This van will need the front end jacked up about 30" to level the master.

You must use the bleeder kit and instructions provided with the master, and pump the pedal full travel slow and easy a bunch of times. Then little pumps just off seat and repeat untill not one little bubble excists. If you are too agressive and "airate" the fluid (get it full of little bubbles) you will have to stop and wait till tomorro when the bubbles have left the fluid.

This system is going to be hard to bleed because there is areas in the lines higher then the master cylinder that will tend to trap air . But you just have to keep working at it untill you get it all out. Usually a hard push of the pedal when the bleader screw opens will blow all the air past the high spots. Most of these vans have the brake lines above the master and this makes it a little difficult to get all the air out. residual check valves will help out with this problem.




as you can see I am trying out a generic disc/drum combonation valve. I allways use residual check valves and I prefer a hydraulicly activated brake light switch due to thier reliability.
Notice the switch is pointing down. If it was mounted any other way it would trap air bubbles you would not bleed it out due to boyency.

The switch is mounted in the rear brake line and afead of the residual check valve because it activates at lower than 10lb so you don't want it on the preasure side of the residual valve.
M1D

Had to go on the hunt for rear wheel cylinders. the factory G10 cylinders are 13/16 dia bore and are hard to find these days. i found two in Toronto Ontario 3 weeks away from me for $85 each

I bought two for a 68 Chevy II which are a 7/8" bore and very commun as they fit many GMs from 63 to 79. Two wheel cylinders and a spring kit in stock locally cost me $32 all in taxes and all.

the difference in the bore size is erelevant considering all the other changes to the van.

http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Wheel-Cylinder-Rear/_/R-UBP37024_0380076334



they are an exact fit, cheep and abundant.

M1d

Bled the brakes, fixed 7 leaks, had to remove some parts to fix them.

This is what you should expect for a brake pedal when using a 1" bore master for manual disc/brum brakes.

When everthing is adjusted correctly and no air is in the system.

Pedal at rest = 8" off floor



Pedal applied normal/ hard braking



Because the brakes have not been driven and seated in there is a bit of pedal increase on first pump, that will go away after a few drives.

M1D

I had stated earlier that I have 1" bore master that came with one of those generic disc/drum proportioning valves and that it was making way too much rear brakes. That was a given because that valve is claimed to be for everything from a 62 biscane to a 78 camaro, which even that claim is BS because there is no way the bias set for one vehicle is right for others. Even in any single year of GM car there could be 3 or 4 different proportioning valves depending on which engine/options where installed.


Any ways: I havethe 90" 2nd gen with 4 brand newsame size tires all around; M1D80TA disc set up and the factory 9.5 X 2 drums using the car "7/8" wheel cylindes in the back.

Too much rear brakes!
Now some people (in the know) have said donot combine two proportioning valves but others have said it not a proiblem. Since I throw away thopusands of dollars on expirementation I left the valving as seen in the above photo and added an adjustable proportioning valve down stream about parralel to the engine fan but accesable through the dog house.

Excelent choice! wich my rear tires set at 30psi and 400 lbs added behind the rear wheels I have been geting rear lock up before and now I was am able to adjust so all four wheels brake evenly. I removed all the wieght and again I was able to adjust the rear to make all four wheels lock up and skid evenly with an empty van( MT! nothing, no interior or anything)

I am very happy with this set up. It has a high very solid pedal that needs about the right foot preasure for manual braking. In fact I dare say its better braking than my 4 wheel power disc in my 65. Yes its better braking!!

Partly why it works better is because the "combonation valve" I installed provides "front brake hold off" , " deferential preasure switch" and its proportioning valve ; which does the most of the proportioning provides a true proportioning conparison of the front brake preasure to the rear brake preasure. Then the adjustable valve down stream alows for fine tunning of the rear brakes.

I am very happy with this set up.


M1D