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Here's a question, why are mechanical brakes no longer used?

Anyone?

Because hydraulic brakes are safer.

Why aren't single line master cylinders being used?

Anyone?

Because dual line master cylinders are safer.

Here's another question, how many people drive their Packards more than 5,000 miles a year? I'm betting not many. How many people have the emergency brake system working to OEM specs? Again, I'm betting not many.

Changing out a single line master cylinder to a dual line master cylinder is just common sense if you drive your car on public roads at all. MOST people understand this. If you own a trailer queen that you have to have a 100% original restoration on then fine, rebuild the original BTV. But if you're driving it on public roads then please, please, for the love of God convert it to a dual master cylinder for safety's sake. WHEN someone is killed by the failure of one of these then maybe common sense will prevail. But I highly doubt it, as the "head in the sand" mentality is pretty rampant with Packard owners it seems. You WILL change your mind when you have a teenage girl on a cellphone in a Honda pull out in front of your grand old Packard and you can't do anything to stop in time before your car cuts hers in half.

Think about that for a while, because every single one of you who think that the BTV and single line master cylinders are safe to use are saying that the originality of your car is more important that someone's life. That's it, end of story. That's exactly what you're saying. And everyone knows I'm right.


And Fred, I don't give two bits where your valve is made, if it was made on Mars with the latest Martian technology I still wouldn't recommend using a single line master cylinder on any car that's driven on public roads.

Eric, hydraulics replaced mechanical brake systems primariy because they are self-equalizing, and far cheaper to produce. Self-equalizing was a huge factor because properly setting mechanical brakes was very time-consuming and probably neglected more often than not, especially when the cars got older and received less professional service. But in the sense of overall reliability, I'd rate mechanicals over single-master hydraulics simply because it's virtually impossible to loose all your brakes.

And it's virtually impossible to lose all your brakes with a dual line master cylinder as well.

I was only debating the first half of your two statements. Of course I can't disagree with the second.

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.