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I recently saw a 1935 Pierce Arrow 845 R/S Coupe that featured a hydraulic-boosted mechanical braking system. The brake pedal looked more like a large accelerator pedal. The owner said the brakes were most effective and required very little pedal pressure to apply. The reason I mention this is to ask if there is a modern hydraulic-boosted master cylinder available that might be more easily adapted to replace the BTV units in Packards?

(o{I}o)

If that's the brake system I'm thinking of that Pierce used, it's not hydraulically boosted. The ones with the pedal like an accelerator pedal use a version of a European system (forget the name at the moment) which utilizes the rotation of the drive shaft as the source of power to assist the pedal. Hence, the faster the car is going the greater the boost.

EDIT - just checked some Pierce sources. From 33-35 they used the drive-shaft powered unit, made in the US by Stewart Warner under license from the Europeans. But in 1936 they returned to a simple vacuum booster as they had used for many years before the adaptation of the Stewart-Warner system.

The drive-shaft powered unit is really quite elegant. Think of it as a disc brake rotor on the shaft with pads, and as the pads grip the disc but cannot rotate with it, the force imparted on the caliper is transferred to the brake linkage.

Does a good working emergency brake mitigate the BTV concerns? After tracking on these discussions I'm tempted to test mine at around 40 mph or so. Is this a good idea or could it do some kind of unforeseen damage? So far I have not had a problem with my brakes but I don't know about whats happened in the cars past. I'm beginning to think that the confusion in this discussion my partially center around how you intend to use your car. If you Hot Rod or if you drive in bumper to bumper traffic or if you simply drive your car hard (often), it sounds like upgrading to disc brakes might be a good idea? If you tend to take the car out for leisurely drives, I suspect that a well maintained system would work just fine. I'm not a mechanic so I don't know for sure.

I think the discussion really centers around "how safe is safe enough". Certainly a quadruple master cylinder would be safer than a dual, but today the dual is considered "safe enough".

Another thing the discussion centers about is which years. There may be one, but at the moment I can't think of anyone who has reported a failure pre 55. As some have mentioned, not widespread in other makes either.

Is that because there are not many BTV in those years in use today or not driven as regularly as the V8's or is it because something changed that has adversely affected the unit.

Heat has been mentioned in speculation since an exhaust manifold appeared and that is all that is readily different. The generational change in units from P2 up all appear vacuum side related, not hydraulic where the failures appear.

The gasket also might come into play since more units have been rebuilt. The S.M. clearly shows a connection from the relief port to the reservoir which the gasket as now shipped prevents.

One of the things that came with my '55 is a 1955 Motor Repair Book. Last night I was looking through the Power Brake section which lists which make used which PB system. Overwhelmingly the BTV was the system of choice: GM, every make but Buick and Chevrolet; Ford, both Lincoln and Mercury; Chrysler stayed away but every "independent" was listed. Does anyone one know if any other make had problems with the BTV or is only Packard blessed?
I do remember that a friend of mine had a '56 Olds 98 2dr Hardtop that the brakes failed on, but I don't remember the exact cause. Knowing Larry, I doubt if he even knew there was a brake fluid level to check.

I believe the last car to use the BTV was Mercedes-Benz in 1962. Hudson and/or Nash also used it.

Quote:

O_D, I was going by what the owner told us when asked about the second "accelerator pedal"; or, maybe I misunderstood what he was saying. Thanks for your research to clarify the situation.

(o{I}o)

Speaking with someone else about the P-A system and trying to jog our collective memories, perhaps the system was developed by Hispano-Suiza? And perhaps the rotating member wasn't on the driveshaft but on a transmission jackshaft. I'll have to do a bit more research to clear up the details. If there's any further interest in this system, I'll update the post when I learn more.

OWEN

The Pierce system was invented and I believe patented by Hispano. Rolls Royce licensed it and used it mechanical over mechanical in the 20's or early 30's, then by the 50's or earlier had mechanical over hydraulic. Last used in 65/66 on the last of the Silver Clouds. I gave owned all of these models so I know first hand. FYI with the new models in 67 they licensed the Citroen common brake and suspension system.

To the best of my memory the BTV wsa original on Lincoln 54-60, Mercury 54-58, Edsel 58, Chev 54-58,Pontiac 54-58,
(lds 54-58, Buick 57, Cad 56&58, Nash 54-57, Hudson 54-57, and Mercedes 56-62???. The spectacular 300SL used it and was raced by amateurs at up top 150mph. I seriously doubt there was a design flaw or it would have shown up back then.

ON the subject of heat. While many makes had the BTV mounted high on the firewall adn away form the manifold, makes other than Packard had them mounted low by the manifold. I have worked on many Packard V8's, never saw evidence of heat damage, never found one hot when I touched it, some had underspray on them which would have burned off if too hot. Heat does not seem to be a problem.

Why are V8 owners reporting more failures?? Maybe because they are more modern with the V8/twin Ul-Traumatic adn more fun to drive. Here's a question, if teh V8'sare inherently bad design, why didn't this show up in the 50's/60's/70's when lots of us and our customers were driving them daily?
My guess is that it's the incorrect gasket/compensator valve problem, nothing else has changed.


Someone mentioned possibly reformulated DOT 3 fluid, if so there would have been massive failures and not only BTV's

ERIC

I have seen thousands of collector cars pre-66 still with single Master cyls, a small % have duals, usually readily availble conversion kits for Mustang/Falcon etc adn 55/57 Chevy. Go to Hershey with 1000+ cars on display. Yes some trailer queens, but the majoprity are driven with single M/Cyls as a dual would have points deducted. They are not fools, I'm sure they maintain their vehicles and count on the orig brakes.

Sudden failure is from a broken hose, low fluid caused by a rusty line etc. A well maintained car will not suffer that very often.

AS to your refusal to answer my question as to where my valves pictured are made. Ina prev post with a photo, you told the person that his valve was made in China or Mexico just by looking at the photo. NOw you reufse my request saying that having a dual master is what's important. Telling the source by looking at it is akin to magic, but we all know the magicians skill is in diverting the onlookers attention. Yes, I do realize that a dual is safer, so are air bags, padded dashes, side door beams etc etc. Now thatI've admitted that, tell all of us a the source of my photos #2 and #3. You, I , and all the rest of the forum members are dying to know.


Fred Kanter
Friend of the turth