Packard Forum Index » V-8 (1955-56)

I believe the last car to use the BTV was Mercedes-Benz in 1962.

HH, as clever as the S-W/Pierce system was, it did not provide boost in reverse, nor did it provide much useful boost at very low speeds (not that you needed much), neither of which was seen as much of a disadvantage. I've only ever driven one Pierce-Arrow with this brake system (a Twelve convertible sedan by Dietrich) and then only for a couple of blocks, but it surely was a memorable experience - a really fine piece of machinery.

I'd guess the impetus behind the Borg mechanical power steering was another attempt to get around the patents on hydraulic power steering. I forget now just who the patentee was but I think he might have worked for Pierce-Arrow. In any case, the date of patent was about 1935 or so and he wanted so much in royaltees that the entire industry decided to wait until the patents expired, which pretty much explains why everyone got hydraulic power steering about the same time.

I'm kicking around a few ideas here about eventually replacing this dreaded BTV but as I am in England would prefer to use parts readily available here which rules out the Ford Explorer/truck parts mentioned in another thread.
Does anybody know if the master cylinder of a 55/56 car with manual brakes is located in the same position as the BTV and is the pedal ratio still 1:1
Apologies if these questions have been asked before but I can't seem to find any info on manual master cylinders except what's in the service manual which tells me it is a 1'' cylinder.
Regards,
Dave.

No to both questions. Not sure of the ratio but probably greater than 4:1 looking at the picture and linkage. In 55-6 master was located on the frame a few inches behind accelerator pedal near transmission. If you pull the carpet away, there should be a removable plate where it would have been.

Attach file:

---

  (16.02 KB)

If memory serves me correctly, I believe in the late 1950s Rolls Royce used a hydraulic pump driven off of the rear of the back of the transmission to provide oil pressure to power steering and power brakes (maybe suspension too). Hydraulic boosted power brakes instead of vacuum boosted. Anyone remember if this is correct?

(o{I}o)

Not sure about RR but sounds reasonable. Lincoln & others also used hydraulic brakes and believe some pumps were on engine front wrapped around crankshaft.

ABS & others have a hydraulic master setup which works off PS pump but it would have to go somewhere else same as the electroboost to get the ratio. It's looking like Packard must have been the only one with the 1:1 pedal ratio so anything modern to retrofit has to take that into account if there is to be much hope of brakes when the assist isn't there.

Thanks for that HH56 all is clear now, I found a site over here with stuff for for kit car builders which sells manual master cylinders and a remote mounted vacuum booster. I was thinking of possibly fitting a manual master cylinder hooked up through this but I think the pedal ratio would probably beat this idea again.
I'm not sure of the booster diameter and will give them a call on Monday and discuss any options they may have.
Dave.

A man uptown has about a 1998 to 2002 Vanden plas. He lifted the hood and i saw what appeared to be a power unit identicle to my Ford unit. Of course if u go to a Jag dealer for anything like that u'll pay a Jag price. It makes we wonder if such units mite be available there in the UK at junk yards.

I'm not familiar with autoparts businesss in the UK. My only concern about a retro fit of any kind is future availability of parts from aftermarket suppliers of special or custom parts (that can wear out) that may or may not be in bussiness 5 years from now or may discontinue offerings.

Edit: i did not check the Jag power unit stud mount pattern to see if that is the same as my Ford unit. It's the stud mount pattern of the Ford unit that allows it to be mounted withOUT drilling any holes in the firewall.

Coorection. The Jag is a Vanden Plas. NOT an XJ6.

I am jot exactly a tecnician but was described of the Pierce braking system sounds much like what RR and Bentley used for many years. The system was also licenced by Hispano-Suiza. It also was inappropriate when driving slowly.

IIrc, RR started using this device with the Phantom I. Last were Silver Cloud III / Bentley S3.

NB: Jaguar belonged to Ford for quite a time, forming the
PAG (Premier Automotive Group) together with Aston Martin and, at least at the beginning, Lincoln.

I found out the boost ratio of the remote mounted vacuum booster I was looking at is 1.9 :1 it is a Lockheed Girling unit as fitted as an upgrade to manual brakes in 60's & 70's and still used by kit car builders. Does anyone know the boost ratio of the BTV...?
I'm still baffled as to how the smaller BTV worked so well when modern 7'' boosters still need a greater pedal ratio, my brakes were fine until last year... would I be right in thinking that reducing the master cylinder diameter from 1'' would give more pressure..? though this would obviously require more pedal travel to displace the same amount of fluid.
Getting sick of polishing and want to drive it now, the weather here in England is glorious today, bright sunshine mid 70's...