Customs dual master power booster upgrade not working

I PMd Two chops and he doesn't seem to want to give me any info. He just said it was expensive to do. Didn't return my request for more info. That was days ago.

 

Some are stingy with information. Information is important, but not as important as what you do with it.

My philosophy is to help those who need help, even if there cannot be an immediate return.

 

I would think you could make changes to that stock assembly to get the ratio more appropriate. Surely you could remove it and send it to someone who could do the work for you. Looks to me like there enough opportunities there to change ratios.

 

Much appreciated, as well! Thanks for taking the time to answer my questions. I have a direction to go with this now...

 

Can someone make changes to the assembly without having access to the car? Like if I had to send it out?

 

Saw that, didn't believe it for a second, then looked at his diagram. That diagram, as posted, will NOT work. The pedal has no pivot. For the brakes to work, the pedal has to push the first lever, which pushes the second pushrod, pushing the second lever. As drawn, it won't do that.

So, let's go old-school: measure the total travel of the pushrod. Then, measure the travel required of the PROPER master (which travel may, in truth, be similar to the one you have). If this matches fair reasonable, you are good.

Get a booster (junkyard is fine, boosters do not die often) from a FULL-SIZE car (unless that heap in your avatar is a Buick Apollo in disguise), and fabricate that in place. Mount up a master with a 5/8 - 3/4 bore, and plumb it without the brake switch, as that air bubble just screws with the whole.
If you can rid yourself of the 'bubble' onto which the Treadle-Vac unit sat, and fab up a flat(ish) firewall, all the better. Tie the booster mounts to the dash if at all possible (as is every factory install, ever), this will help eliminate movement that contributes to poor feel. And firewall cracking that comes from movement.

Here is why you have a hard pedal: You have an inferior booster that produces very little pressure, even when it's working properly. I had one, I KNOW. Then you have a master that is far too large for the application, which requires an inordinate amount of pedal pressure to operate. Line size makes absolutely NO difference in braking, at all. It's only pressure. You could have 1/2 " lines and the only effect it would have is you would need more fluid to fill them. Well, that, and leaks would be more likely owing to a few items that we need not go into here. Residual pressure valves are not cumulative, meaning you could have ten per wheel, and the only effect would be a lot of unnecessary plumbing. They ARE directional, just not cumulative.

And, yes, this is now getting into money, because you entrusted the car to people who had no idea what they were doing. And led you on that they actually DID have knowledge. Sorry, but this whole thread is proof. But brakes need to be done properly.

Cosmo

P.S. IF you opt for a pedal change, I HIGHLY recommend getting the entire unit - pedal, linkage, booster and master from a full-size car (I think I have emphasized that a bit much, eh?) and mount that whole unit to the firewall and dashboard. The other advantage to this is the unit will come with a brake light switch, too. Then you can flip masters around for bore size to optimize the braking.

P.P.S. Those guys who told you their cars stopped just fine: ask to drive the car. Many, many, MANY people lie about their car's abilities. Really. It's just hard to admit that you screwed up and the car is compromised in it's ability due to your screwup.

 

Thanks for the reply, Cosmo. This is very confusing because I have some people saying the booster I have, (albeit a USA made aftermarket one according to the seller from Illinois) is more than sufficient and then you and a couple others suggesting one off a full-size 'heap' like mine, so for someone like me who has never done this before, that can be hard to grasp. Anyways, I did contact Booster Dewey in Oregon and he has a rebuilt system, complete, from a full-size GM van from the mid-70s. It's going to have to wait if I try that because I've expended my budget as far as i can afford right now...YES, spending it at garages that despite their best of intentions, beyond their area of expertise.

As for the master, many people have made mention of the fact that the manual brake version of the 58 Buick used a 1" bore with the same size wheels and though the power treadalvac version had a 21/32" bore size (practically a 2/3 or 4/6) that the treadalvac system is so different than a modern booster system that they can't compare and a 1" bore should be fine. What are your thoughts on that?

 

The diagram is not correct as marked - you skipped a pivot and couple lengths for the links. We could review all that and do a bunch of math - OR- let's skip directly to the answer: There is no free lunch! Meaning put as many links, pivots, bellcranks whatever you can think of it all boils down to one thing ( ok 2 things) - how much MOVEMENT IN versus how much MOVEMENT OUT (perpendicular to the pivots of course)- THERE'S the ratio - everything in between is just "noise" and is only good for confusion. If I push the pedal 6" and the mc plunger rod moves 1" the ratio is 6:1 - doesn't matter how much clap trap is in between.

 

The bigger bore of the master cylinder will increase the pedal effort. There is quite a spread between 1 inch and 21/32. That will make a difference for sure.

read this from Mark Williams

One of the most common misconceptions is that a larger master cylinder will create more pressure. While a larger master cylinder creates a larger displacement, it takes more force to create the same pressure as a smaller bore. While a larger master cylinder will take up system slack with less pedal stroke, it will take more force to create the same system pressure. The result after adding the larger master cylinder is a harder pedal which needs much more pedal pressure to create the same amount of braking force. For instance, moving from a 3/4" master cylinder to a 1" requires 77.7% more force on the push rod.

My brake pedal had 2 holes from the factory, I just moved the clevis up, but you could pull your pedal and drill it yourself. If it doesn't help just put it back the way it was.

I don't think you did anything wrong, I think the setup you have has a problem. MC or booster NFG.

 

This is my pedal assembly. Not sure how I'd make the mods you were mentioning with the way it is designed...

 

No help from me, Joe, let me just jump in here and say that this is the HAMB at its best, really good thread.

The HAMB feels like Hot Rod University sometimes, where you get to wander the halls, pop your head in the door, and help yourself to a seat in the back. It is fairly easy to cipher who knows what they're talking about and who does not, so you just tune out the noise and soak in the knowledge. Working on a brake system myself, this stuff is gold.

Now, back to the class . . .

 

The pedal pictures in the link below looks the same as RetroJoeG's drawing, and should help clarify the design and operation.

http://www.ebay.com/itm/58-BUICK-SU...Parts_Accessories&hash=item20d4c173c0&vxp=mtr

 

It's kinda simple, they are lying. Like I said, ask to DRIVE the car.
It's kinda like people who told me an Evo Harley was reliable. I bought one brand new. They had lied to me.

Bullshit and different pedal ratios/arrangements. It's bullshit that just because a booster operates a bit differently that that will somehow rearrange the physics of hydraulic leverage. The booster operates a hydraulic cylinder which produces pressure. HOW the booster works is of no consequence at all. That is like saying that a compound bow somehow cannot hit a target the same way as a medieval recurve bow. It's bullshit: HOW the arrow got it's boost does NOT affect the actual flying. They, too, have no clue of what they are speaking. Please stop listening to people like that, they are wasting your money. As to the manual version working with a 1" bore, quite possible, but not with that pedal linkage. Get the manual pedal linkage, then we'll talk.

The most successful braking arrangements I have built revolved around adapting factory parts without changing the basic design. The least successful braking arrangements have revolved around accepting aftermarket parts/designs. Practically NONE of the aftermarket actually DRIVE the cars. They build the cars and parts so you can reasonable safely drive the car up onto a trailer, where it will be tied down awaiting the next show. I know many will argue, and I may have experienced only those who DO this, but it still follows that the designs of engineers who get paid for it, have billions of dollars riding on the success of their designs, and WILL be fired if designs don't work, are better designs to adopt than those of people who do not.

One of my experiences, a very bad experience, was with a Very well known name in M-II suspensions. Besides the whole suspension breaking out of the car, there was this clue: when I went to pick up the suspension at the factory, in June, there were NO STREET RODS AT ALL in the carpark. None. Late model cars and trucks, nothing that could remotely be considered a 'hobby' car. This SHOULD have been my clue.

Cosmo[/QUOTE][/QUOTE]

 

Here is the missing 'link' to this diagram: The 'pivot' at 'A', is not a strictly a pivot, it is also where the link 'B' is welded to the brake arm. The pivot 'B' is not a pivot, it is a stop, which keeps the pedal arm from over-retracting. With that in mind, the diagram now makes perfect sense. And the pedal ratio math is all wrong.

It's NOT 2.4:1.

Cosmo

 

[/QUOTE][/QUOTE]

OK, it is true that the pedal assembly used on the manual versions with the 1" bore WAS different according to Frank Lyle who owns 37 models of the '58 Buick. So...what you're saying makes sense to me now. Is it your thought that if I purchase a manual brake assembly from him it will work much better with 1" bore masters?

I spoke again with the gentleman who had modified his system, but not the pedal and he did confirm that his pedal does feel higher and harder than normal. Can't drive it myself because he's in CA and I'm in NY. In the meantime, I also found a mechanic who had a customer with the same car and upgrades that I did come to him complaining about the same issue I'm having and he said they removed the plenum, fabricated more metal to strengthen the firewall and bolted the assembly directly to that and used an aftermarket pedal with a 5:1 ratio and it solved all the issues.

 

So I guess the best way to calculate it is to measure the travel of the pushrod vs the actual travel of the pedal?

 

Completely agree! Appreciate all of the feedback and perhaps others can learn something and benefit from this thread, as well

 

The simplest solution, to me?? Get a booster (bet you thought I'd say full-size car), get a master with the same or SLIGHTLY larger bore than OEM. Plumb it in. Drive.

The reason you asked about pedal ratio: you altered the master/wheel cylinder ratio. There is no real reason to know, or change the pedal ratio, in a stock car. You may assume the Buick engineers knew what they were about. Same with the master bore size. The booster is what you wanted to change, no need to alter the entire universe.

Changing any of the ratios from stock WILL cause issues that require a certain knowledge to repair. This is where you failed, you altered certain ratios. Bring all back to stock ratios, and all will be good. Alter nothing of which you have little knowledge.

At this point in the thread, I'm not even sure why you went down this road. A new Treadle-Vac, in a stock Buick, would have been the economical solution. Perhaps from another vendor. Or simply change the master, leave the Treadle-Vac unit alone, if possible.

Cosmo

 

I wanted to change from a single master to a dual because I was told it was a safer way to go. I had a failure with my original rebuilt Treadalvac system and had no brakes. Luckily I was able to cruise into a field, throw the car in neutral and turn the car off without any injury. Better than it happening in traffic. Not trying to change the entire universe on the car...no desire to change the wheel size. The Treadalvac system I have does not allow you to change the master or the booster separately. It's all one unit and can't be altered, otherwise I'd have opted for that option. Trust me. That would've been a lot easier.

Joe

 

Someone failed to mention just HOW costly "safer" really is, didn't they? That, and the cost of listening to people who may mean well, but really have not a clue.
Failure of the main hydraulics is rare, yet it sounds like you also had a failure of the backup braking system as well, which also needs to be addressed.

Cosmo

 

Can't argue with that. Lost a lot of money on this, which is why I turned to you guys for some good, knowledgable advice. Thank you. I'll be posting a photo link to my actual assembly soon just to at least clear up how the pivots actually work vs. the illustration.

 

I'd first check to see if the booster is working. Get one of those hand vacuum pumps and hook it to the booster pump up 15 to 17 inches of vacuum then push on the brake pedal there should be a small drop in vacuum, then release the pedal and there should be a big drop in vacuum.

 

Still chasing wild geese?? No need to suss out the pedal assembly, it is fine. Suss out instead the master cylinder/booster. That is where your problems lie. Might as well determine the rotational speed of the heater blower, it'd make as much difference.

And we've told you how to fix the master/booster.

Cosmo

 

Holy geese! 1500 rpm.

 

The first booster they sent us with the kit was not working. They had left that installed and I drove all the way across town to the 2nd garage, which does fabrication and classic restorations. We did perform that test there with 18 inches of vacuum and determined that it was faulty, then tested the replacement booster, which worked fine, before installing that. Hard pedal came back after the master was bolted on.

 

When installing the booster does the did you have to push the rod in to hook up the pedal? If so that is the problem.

 

[/QUOTE]
I also found a mechanic who had a customer with the same car and upgrades that I did come to him complaining about the same issue I'm having and he said they removed the plenum, fabricated more metal to strengthen the firewall and bolted the assembly directly to that and used an aftermarket pedal with a 5:1 ratio and it solved all the issues.[/QUOTE]

You just found your solution. Much easier than trying to make that complicated factory linkage work with something it wasn't designed for.

 

No, we had to add a rod extension.

Yes, very possibly, only thing is that plenum is part of the air duct system, so I wonder how losing that would affect it...

 

The treadle-vac brakes in late 50's GM cars used a completely different brake pedal linkage then the same car with manual brakes. The treadle-vac booster was not located in line with the brake pedal like what we think of as normal. That's part of the reason for that weird bell crank arrangement. If you can get the hanging pedal assy. from a manual brake car and swap it for the one you have and then mount your new booster/master cly. assy. to that you should be good to go, except for a few other problems like the way the brake light switch was installed. This is a common problem on 55-57 chevys when you convert from treadle vac brakes to "normal" power brakes.
Also if you change you pedal assy.,don't throw any of the old stuff away. The 58 restorer guys pay good money for those parts.

 

This is why I was pushing for tossing the original pedal setup. Mathematically, it ain't gonna fly, no matter how much the keyboard engineers want it to.