NYsquarebird58's Brake System Overhaul and Disc Brake Conversion

[RustyNCa]

OK, so I installed the 1" master cylinder yesterday. It seems to have done the trick regarding pedal travel and effort. It feels good now. I don't have to push down quite as hard, and I have a bit more peddle travel. It's certainly not a night and day difference between the two, but the for my setup the change was just right.

There is a problem, though... Under moderate braking my rear drums lock up! It's not fun. If I have to make a sudden stop, I'm in trouble. Last night I took the bird up to about 70mph and brought her down to a gradual controlled stop. She stopped fine, but I had to be real gradual on the pedal.

I can lock the rear wheels only going 10 or 15mph. it doesn't take much.

The rear brakes locked up the same way with the 1-1/8" MC as well, so I know it's not that.

Any ideas?

Photos are a bit small for me, but it looks like you are running the same setup I am on our 58. The combination valve is adjustable, I know I had to spend some time adjusting ours because I had mostly rear brake at the start. Also make sure you are using the right output for the front brakes, I think at first I had mine plumbed backwards also. The bigger of the two reservoirs is for the front disc brakes.

What I had to do was take some tools along and start changing the setting on the valve till I had the right amount of Front vs Rear brakes setup in it. Before I did that I could mash on the pedal and the car would slow, but not bite hard on the front.

[NYsquarebird58]

Photos are a bit small for me, but it looks like you are running the same setup I am on our 58. The combination valve is adjustable, I know I had to spend some time adjusting ours because I had mostly rear brake at the start. Also make sure you are using the right output for the front brakes, I think at first I had mine plumbed backwards also. The bigger of the two reservoirs is for the front disc brakes.

What I had to do was take some tools along and start changing the setting on the valve till I had the right amount of Front vs Rear brakes setup in it. Before I did that I could mash on the pedal and the car would slow, but not bite hard on the front.

Hey Bryan,

My master cylinder is a 1" bore MBM MC1921H and my Combination valve is an MBM PV2. My master cylinder has the same size reservoirs for the front and back so I don't think that's an issue.

Where on your proportioning valve do you adjust it? Yours looks similar to mine, but I don't have an adjustment.

Here's a pic of my proportioning valve and how I routed my lines.

[NYsquarebird58]

Maybe the problem is that you have the disc output of the master cyl plumbed to the rear drums? That might explain why you have such good braking on the rear and not so good at the front? In the references below note that the front and rear outputs are reversed on one style of master cyl. Did the master cyl you selected come with the details as to which output goes where?Eric

My reservoirs are the same size on the front and back of my master cylinder and It's my understanding the pressure coming out of the master cylinder is the same on both sides. I don't think I could plumb this particular master cylinder the wrong way.

It appears you have the brake light switch hooked up to the front line? That will cause that switch to go bad sooner with the higher pressure.(hearsay only - no experience on that but the switch was designed for the lower pressure drum system). The switches are pretty cheap - I'd just leave it and see what happens - change it if you need to later.Eric

I spoke with "Old Irish Dave" earlier. He says he prefers the master cylinders with ports on both sides, because he likes to screw the hydraulic brake switch directly to the master cylinder on one of the unused ports. Also, if you look at the original master cylinder on our squarebirds, the brake switch is screwed right to the end of it.

I'm making the assumption here that the line with the switch in it is the output for the front discs since it is plumbed to the front input of the proportioning valve....and from the proportioning valve I'm guessing you ran a new line to each front side from the two front outputs? (at least that's how I did mine).Eric

Correct. Here;'s my setup.

You did separate the front and rear systems right?? (by removing that junction point on the frame near the steering box?)

That is a disc/drum proportioning valve - right? If it were a disc/disc prop. valve with the drums on the rear - hummm.

Just a few guesses. Eric

Yes, I ran all new lines and removed the old junction block up front.

I'm still amazed at how well those booster brackets turned out.Eric

Thank you! Fabricating those was probably the funnest part of the whole project.

Some really good reference.....these are the folks that helped me when I was doing my conversion.
http://www.mpbrakes.com/uploads/docu...lumbingpdf.pdf

http://www.mpbrakes.com/uploads/documents/optomize.pdf
Eric

Great articles. Thank you!

I used a Lincoln Mark V? disc/drum brake master cyl and a disc/drum proportioning valve from master power. No nose dive - no rear lock up and about the same pedal pressure as the drum system. The master cyl lines come out the wrong side but it worked so well I just lived with it (basically it was all I could find that would fit my Frankenstein* system 10+years ago)

*Ahem...... I mean my custom hot rod highly engineered super performance braking system.

Seems I found later that a Mustang ('68?) is the same master cyl with the outputs on the other side - may change it someday. Eric

Those scarebird brackets really made the job so much easier for me!

You've done a super nice job on the documentation here and it's much appreciated. Geezzz I remember those days well. Almost think you cheated by getting to use the scarebird brackets. But then cheating is allowed in Squarebird brake mods..... :-)

Eric

Thank you, Eric. It seems like we all struggle just a little less than the guy before us. Hopefully the nest guy who decides to do a disc brake conversion struggles even less. I'm happy to post and snap off plenty of pictures to help others out.

[NYsquarebird58]

I'm going to try something out. Since it appears that I have too much braking pressure at the rear drums, I'm going to try an adjustable proportioning valve.

MBM APV-1

Here's the product description:

A necessary part of any performance braking system! This black proportioning valve features a rotary knob with a knurled grip to allow for the finest incremental adjustment of front to rear brake bias. This further enhances the effectiveness of the entire system to prevent that dreaded rear brake lock-up by reducing line pressure up to 60%. Includes 2 adapter fittings for use with 3/16'' brake lines.

Hopefully this does the trick.

[simplyconnected]

The beauty of an open forum is, we like to hear everyone's input. Marcelo and I had a long conversation regarding his lockup problem and I urged him to call Old Irish Dave since he's our 'brake guy'. My prior posts suggested, he should bed-in his shoes.

Dave is getting out of the brake business and moving to Alaska but he still supports his old customers. In Marcelo's case, Dave recommended he use this black MBM valve. I think this is WAY too early to throw parts at the problem for many reasons:

Here's what Bendix says: "What’s causing the drum brakes to lockup?
Rust, on the surfaces of the drums and often on the brake shoes themselves, can cause the parts to grab. Cheap drums, with inferior metallurgy, are prone to the condition. It’s worth knowing, though, that until a layer of friction material from the brake shoes has been embedded in the working surfaces of new or resurfaced drums, even good drums may be somewhat susceptible, too. Shoes with a high metallic content may develop surface rust in humid conditions rapidly enough to make the problem even more likely."

Marcelo's brakes are far from 'bedded-in'. His charging system isn't working, the battery is dead, and the car hasn't gone anywhere. Marcelo just learned about D1 & D2 a few hours ago and thought his car was awfully 'doggy' because he never used first gear, and couldn't understand why it wouldn't downshift. In short, he's still learning how his car operates. Once he starts driving it, many things will straighten out for him.

I'm going to step up and agree with Kultulz regarding brake cylinder size. Instead of using that black box, which is really a non-temperature compensated flow control valve, I suggest Marcelo first beds-in his shoes. If he still has too much rear brake, he can use smaller-bore rear brake cylinders. They don't exert as much pressure on the shoes for the same brake line PSI. That is what I did on our Galaxie and it has been working great for two years. The '59 Galaxie rear cylinders are the same part numbers as Squarebird's, but in a heavier car. I asked Marcelo to measure the bore of the brake cylinders he removed from his rear brakes, and am still waiting for an answer. They should be 7/8".

In the mean time, I sent Marcelo my OEM voltage regulator from our Galaxie and he received it yesterday. For the sake of six screws, he should be back in 'battery charging land' again and his GEN light should work normally. I hope he takes the old gal out and gives her a good run for a couple/few weeks. Then, he should talk about making a move if need be. - Dave

[KULTULZ]

Just a quick mention on adjustable proportioning valves.

Unless one has a set of gauges and/or a skid pad, such a device can really cause heart break.

That valves' only function is to limit pressure to the rear wheels in case of a very hard and/or panic stop.

Research fully on how to set up. The combination valve (CHEVELLE) that came with the kit (GM) should be fully functional and have close to the correct bias. Make sure your rear foundation brakes are sound before spending the extra money.

[RustyNCa]

Just a quick mention on adjustable proportioning valves.

Unless one has a set of gauges and/or a skid pad, such a device can really cause heart break.

That valves' only function is to limit pressure to the rear wheels in case of a very hard and/or panic stop.

Research fully on how to set up. The combination valve (CHEVELLE) that came with the kit (GM) should be fully functional and have close to the correct bias. Make sure your rear foundation brakes are sound before spending the extra money.

I remember my valve came with instructions of how to adjust it after installation, till I followed those instructions to adjust the valve the front brakes wouldn't lock down completely and the rears seemed to be doing to much of the work.

It's been to long, I don't even remember who I got the parts from anymore, but I do remember they also had the instructions on the tech section of their web site.

[DKheld]

I was just thinking that if it is a bad idea to use a drum type master cyl on a disc brake system it would follow that it would be a bad idea to use a disc type master cyl on a drum system. Maybe a disc/drum proportioning valve should compensate for the added pressure going to the rear drums from the disc output of the master cyl but in this case it sounds like it's not working or it's not a disc/drum proportioning/combo valve? Yours has the black cap covering the metering valve so seems like it should be set up for disc/drum but guess the input is looking for drum pressure coming from the master cyl not disc pressure.

When you are only using one valve it should incorporate metering and proportioning - they are designed for different systems at least the ones that Master Power has (and I have a feeling they all come from the same supplier) - "Combination Valve - A combination valve incorporates metering and proportioning into one valve. These are available for disc/drum or (not and) disc/disc systems."
http://www.mpbrakes.com/technical-su...nce-valves.cfm

Heres how to change the combo proportioning valve that Master Power sells from disc/drum to disc/disc so it seems yours should have the metering valve installed to be correct for a disc/drum system. If not it is for a disc/disc system and you'll have to add that adjustable metering valve for the rear to bring the pressure down? Maybe you need to add it between the output of the master cyl and the rear input of the proportioning valve (JUST A GUESS) That's why I was asking what the valve was set up for - disc/drum or disc/disc. Doesn't mention adjustment to the valve so may be different from the one RustyNCa has (or yours).
http://www.mpbrakes.com/uploads/prod...60_Rev8_08.pdf

I'm thinking that because I used a disc/drum master cyl and a disc/drum combo/proportioning valve could be the reason I didn't have any trouble......because I know my luck didn't have anything to do with it.

IMHO anyway....
Eric

You can sort of see the metering valve (for disc/drum) installed in my combo valve rats nest (black cap removed). Think I told you before but I had my combo valve below the master cyl and it seemed too close to the manifold so at the last minute I moved it here on the frame. Since it all worked so good I never re-bent the lines - just enjoyed the car for a while.


and added the brake light switch to the old input of the junction block and the output to the front lines became the input from the combo valve - line going to the rear stayed where it was originally.

[Tbird1044]

Which model of proportioning valve did you use?
Also, the rear brakes have a smaller wheel cylinder than the front brakes. It may pay to check that the correct wheel cylinders are installed. One never knows what has been done to these cars over a 55 year period.
Nyles

[NYsquarebird58]

Which model of proportioning valve did you use?
Also, the rear brakes have a smaller wheel cylinder than the front brakes. It may pay to check that the correct wheel cylinders are installed. One never knows what has been done to these cars over a 55 year period.
Nyles

Hey Nyles, the entire brake system was overhauled. I used new uninstalled parts from my previous '58 to overhaul the rear drums and discovered that the wheel cylinders are different diameters from what comes stock on '60 birds. The slight size difference in bore on the wheel cylinders and the brand new shoes that were not yet arched to the new drums is most likely the contributing factor to the braking performance issues I was having.

[Randy]

Thanks

I wanted to say a big Thank You to Marcelo, for this thread, I know its a lot extra
work to Document and take pictures,I looked at it a few times. and sorry for
your finger Ouch.

............................................................ ................................

Now I have to start on this side, and not to worry that wood is just sitting there. its on jacks

[NYsquarebird58]

Hi Randy,

Thanks for the kind words. This really is a great community. Prior to my disk brake conversion, the most I'd ever done to a brake system was change a set of pads. I owe everything I've learned to this community, and especially our webmaste and my friend, Mr. Dave Dare. Glad my thread is a help to you and others.

Thanks,
Marcelo

[Randy]

..Yes Dave Dare
My Mentor helping me all the way, Thank you Dave .(INVALUABLE).He told me to used your therad,

[simplyconnected]

It's members like YOU who make our site one of the greatest Thunderbird sites on the planet.

Everything Marcelo does it to perfection, and he's into a lot of disciplines. If you want info about classic telephones or fans, Marcelo is the go-to guy. He has restored countless units that look absolutely 'factory new'. He even uses a phone from the 1920's at his house to answer calls. Amazing, and so cool... You see the quality of work he has documented on his 1960 Squarebird, it was beautiful and I think he got top dollar when he sold it. Even though Marcelo no longer has a T-bird he still maintains his pictures on photo bucket for OUR benefit.

Randy is another guy I take my hat off to. Randy has wrestled with Dyslexia all his life but that doesn't stop him from fulfilling his dream. Randy never restored a car before so his Squarebird is the first. He has learned a tremendous amount by restoring his suspension. He is also retrofitting power disk brakes including all new lines.

Marcelo did such a nice job on his car, that I steered Randy to Marcelo's pages and photos. Our site is one that truly helps other restorers who may live around the world or down the street. That is Alexander's legacy and I'm proud to be part of this family of members. - Dave

[Dan Leavens]

Mr. Dave, well said and your contribution and others does NOT go unnoticed by this site and its members.
Thank you for what you do to for our squarebird site and as I have always said " The best TBird site on the planet "