Re: 1956 executive disc brake conversion kits

Posted by JeromeSolberg On 2020/5/2 0:06:28

Many, many people have tried to find a way to adapt modern power brake systems in place of the Bendix Treadle-Vac in Packards, including myself. There have been a lot of attempts, non very satisfactory. The biggest issue is that the Treadle-Vac in the Packard is mounted directly to the pedal, without a linkage. It has a small effective master cylinder bore (5/8" if i remember correctly) and a very long stroke, which allows it to provide leverage (small master cylinder bore operating on a large slave cylinder bore, with a long stroke). Modern Delco-style brake boosters/master cylinders are mounted up high on the firewall, and get their leverage from a linkage. They have 1" bores typically and a much shorter stroke, and of course if they are dual circuit they have 2 pistons. You need a 2.56:1 linkage at minimum (2 x 2.56:1 ~ 5:1 for a dual circuit system) to match what the Treadle-Vac was putting out ( 8/5 squared ), and from what I understand most are between 4 and 5:1, it's a function of slave cylinder bores, and whether you are running disc or drum, etc.), so you might need this kind of pedal ratio, depending on what the disc brake system you were adapting was designed for. Very complicated! Easy to spend a lot of money and get something that doesn't work!

The few possible solutions to this involve designing your own linkage and putting a modern power brake system (look back, I think people found stuff from mid-1970's Lincoln's would fit) up on the firewall in place of the Left-hand-side air circulation vent. But that's not a very nice solution!

Ideally, someday Wildwood or someone would make a 0.44" bore (you have to go even smaller because of the two pistons for the dual-circuit) long-stroke dual-master that could be mounted to one of those compact dual-chamber boosters and go right under the floor where the Treadle-Vac was. But such a thing has yet to occur, and I doubt that it ever will.

Most people, myself included, have come to realize that the brakes, at least on the Senior Packards, are o.k., if not asked to do too much. If you are in a situation with a lot of hills, etc., use low range on the Ultramatic, or shift down to a lower gear. Don't be afraid to stop/slow down and let your brakes cool off if you feel them start to fade.