Packard Forum Index » V-8 (1955-56)

Here are two master cylinders with 5/8" bore size according to Summit's website. They don't give any information about the stroke though.

My biggest concern with the way that ABS Power Brake makes their system is the fact that the brake pedal looks low to the floor when compared with the original brake pedal in relative location to the gas pedal. Craig's pedal was similar to how ABS does theirs, however, I haven't heard much feedback regarding this conversion that others have similarly done. Blocking off the air vent and putting it on the firewall is not really a good option for me since I live in a hot environment in the summer, unless I put aftermarket air on the car.

ABS mentioned that they were measuring the pedal ratio from the pivot point on the pedal to the center of the pad as well as where the bolt is through the pedal arm from the booster to the pivot point.


Links to 5/8 Master Cylinders:

https://www.summitracing.com/parts/ceb-130-45402

https://www.summitracing.com/parts/ado-18m1192

Well, those are all interesting. The first one is for a Mazda GLC and similar, it has a chance of fitting the Ford Courier booster since that was a Mazda product as well, maybe the booster that naturally fits these is 7" or less as well, haven't looked. The second one is for a Nissan Sentra. None of these are for particularly large cars, but they did use disc brakes (at least on the front), from what I understand disc brakes require more cylinder volume than drum brakes, but really it's dependent on the stroke and probably not possible to know unless one gets one. They could also have issues with balance front/rear, again hard to tell unless one got one.

The position of the bolt on the pedal arm doesn't necessarily have anything to do with the pedal ratio. It's the ratio of the distance from the pedal to the pivot axis, to the distance from the master cylinder axis to the pivot axis, measured perpedicular to the master cylinder axis, like in the attached diagram. Maybe they can measure it according to the attached or similar diagram.

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Addendum: There is an interesting reverse swing pedal setup in the post after the 90 degree illustration at the link in the next paragraph. Mounting the Electro master under the dash or maybe with a bellcrank at 90 degrees with a remote fill container in the engine compt might also be an option.

On my conversion, it has been several years since I did it and don't know where the sketches and details are at the moment. As I recall, my final pedal ratio wound up at just over 3:1. Lower than I would have liked but much better than 1:1 original and quite serviceable even with no vacuum. Raising the pivot allowed for a longer arm to help increase the ratio as well as position the takeoff closer to the area of the vent opening needed for a better input to the bellcrank. I was first going to use something like the tri 5 Chevy bellcrank arrangement which allows a master to fit parallel to their firewall under the dash but instead opted for something more open that I could install in pieces to be able to build in stages and have the rods be in a different plane to cross over one another. Also wanted to be able to add reinforcement and support plates to the vent area without taking the dash completely apart so that too prevented a one piece already constructed assy. Added benefit was being easier to fit the split bellcrank in individual pieces to the space between the firewall and flapper valve in the original air duct.

The first attempt at a new pedal with increased ratio was a straight but longer arm which as I recall positioned the pedal near the original location heights but maxed at roughly a 4 inch stroke before it touched the floor. That wound up giving I think less than 3/4 inch of stroke at the master which again by memory only was capabe of something like 1 1/4. Adding the angle raised the pedal and gave closer to 7"before the floor which increased the master travel to over 1" Not quite at the max available but close enough to have a bit of safety with the fluid volume out. Can't remember if the current booster is a dual diaphragm 7 or 7 1/2 but is quite capable -- too much so in fact as I barely need to touch the pedal before meeting the windshield. Have a new single 7 booster I was going to try but that is basically when I lost interest and stopped working on the project. Because of booster position and the extra linkage and arm weight I also found need for a helper pedal return spring so added a torsion spring at the extended pedal pivot support. All that linkage weight would be eliminated with a different booster arrangement.

Unlikely I will ever work on the car again but were I to try something with the ElectroBoost would do roughly the same except instead of the multi piece bellcrank would try to make it a single triangular piece like the Chevy but housed in a short length of steel tubing approx the width of the Electro master. Weld a plate on to use for attaching the master. As long as the master cleared the firewall side the tube could be shorter and plate could be longer than the master width because it could be offset to overhang the regular vent tube slightly. -- Tube diameter would be around 5 1/2 inches slightly over the size of the vent opening flange so it could fit over the flange and be able to use that as a location assist on the engine side of the firewall. Individual reinforcing plates could still be slipped in the vent opening to be placed on the inside. Need to figure out how to reattach the original vent tubing and orientation and angle of the output rod and would depend on where the master would work the best. If the master over the opening was not sufficient a small rubber bellows on the inside over the output rod would prevent air and fume issues on the passenger side.

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Andrew, Would we be able to get a picture that shows the linkage from the side? I believe that would help everyone understand how that system works.

Like you I am trying to find a solution for a dual master cylinder. The issue for me is I see the mount for the brake pedal in your picture to be a little more left, which may cause a problem with the clutch pedal I have in my car.

But I would be interested in seeing some more of the compact linkage ABS has. I have read an article of someone adapting a tesla Ibooster (electric booster) into a volvo. The GenII is similar in size to the ABS unit, but benefits from the point that it is standard OEM equipment. The bore however is closer to 1-1/32.

https://www.evcreate.nl/installing-the-ibooster/

On the iBooster (Bosch) unit I didn't see much in the way of size specs. Is there info as to physical size of the overall unit, recommended ratio and stroke length needed for max fluid out?

The overall unit on the EVcreate site looks about half the length of the vacuum booster and master but maybe a similar diameter?? If so, was thinking it might be possible to make a dual stage ratio conversion package that would use the original pedal and bolt in the original spot on the engine side as per the BTV. The Tesla could bolt on the end of that package at the BTV downward angle or if still too long maybe be angled so the Tesla master end will be able to miss the steering box. The actuating rod looks rather long so wonder if that could be changed.

Another question might be how expensive is the Bosch iBooster unit vs the Electroboost. From what I see available Bosch units from Speedway look similar and somewhat comparable in price to the Electroboost. A unit on Ebay listed for a Honda looks more like the Tesla Gen I unit on EVcreate and is less expensive. Also, what kind of support or parts would be available if it needed something down the road. As I understand it the ElectroBoost uses standard US available parts. Not sure how available Bosch parts are.

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So if you look at the other links on the site the master cylinder bore is 26 mm. The GenII has:

"the length from flange to the end of the reservoir is 39 cm but to the end of the master brake cylinder only is 24 cm. Center to top is 10 cm and to bottom is 16 cm..."

I did see the actuating rod does look rather long. I would have to get one to determine how that compares to the BTV and how it attaches.

That blog post did have a section testing the performance of the system. For what ever reason the link is no longer active. Ill try to keep an eye on it. I do have access to a 21 model Y that I plan on crawling around in to see if I can get measurements on the ratio.

as for part availability this set up is used on the Tesla Model 3 & Y as well as the honda accord (according to that website). I have seen this booster/master cylinder set up go on ebay for $300-$400. Another source would be to check out the website car-part.com. That searches salvage yards nation wide (including up into Canada). The wiring can be purchased from that individual or one can make make their own if they can follow along with what he did and get the components from a yard.

I am not to sure how ABS compares price wise.

I just updated my earlier post. The Gen I Tesla unit looks to be a Bosch unit and there is one on ebay listed for a Honda that looks very similar. Question on the Honda would be is it more or less stand alone like the Tesla version or rely on too many ECM module inputs like one of the Ford versions the EVcreate site looked into.
https://www.ebay.com/itm/313618587484?chn=ps&norover=1&mkevt=1&mkrid=711-213727-13078-0&mkcid=2&itemid=313618587484&targetid=4580496732614413&device=c&mktype=&googleloc=&poi=&campaignid=418233788&mkgroupid=1230353745471221&rlsatarget=pla-4580496732614413&abcId=9300542&merchantid=51291&msclkid=28ffdf4f68a71d10966ebd4dc5f36bab

Here is the Speedway Motors ElectroBoost lookalike. For that matter, maybe it is the other way around and the ABS unit could be made by a Speedway vendor. ABS does seem to have more master configurations though. Using this one would need to see if there are other models or else plan on some additional parts maybe in the way of proportioning or metering valves needed for drum/drum or disc/drum.

Both the Gen 1 and the Gen II are both Bosch units. And the honda does look similar. Though the EVcreate site does mention a Honda Accord as using the Gen II Ibooster from Bosch, I am not to sure of the differences between Honda and Tesla. But if it is similar internally to the tesla than it should be the standalone unit.

EVcreate does mention about proportioning valve and residual pressure valves when dealing with drum brakes on the rear or all four corners. They list some recommendations as well.

The Bosch iBoosters that I know about have mc diameters of 19 or 22-25 mm, and also use pedal ratios of 3 or 4:1 (what I would call normal pedal ratios)
They also need a pretty beefy power supply, I think they have a 30-40 amp circuit breaker as supply voltage. You would also have to do some wiring from the internal travel sensor to the iBooster ECU, but that is just 4 wires. The unit would also expect wheel speed signals, but should still work in a default mode without them.
I am enjoying reading this thread, but I plan on sticking with my easamatic.

The size of the iBooster unit looks fairly large and wonder if it would fit in the stock location any better than a vacuum unit. No dimensions given but it looks fairly large in photos and unit weighs around 4.8 kilos or about 10 lbs. Maybe the photo is deceiving but it looks fairly tall. Maybe that particular section on the bottom could drop into or hang below the frame. I am thinking size wise the two piece ElectroBoost layout might still be a better option if trying to use the original location.

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