Adjusting Self-Adjusting Brakes

[67Survivor]

You could retrofit a Lockheed brake booster. SS sells a 7" for $300. VB has the 7" and a 5".

 

[Mike Armstrong]

You could retrofit a Lockheed brake booster. SS sells a 7" for $300. VB has the 7" and a 5".

Thanks.

Sure like to hear from those that have used this model brake booster about what their experience gas been.

 

[Chuck Ingram]

Mike

Seeing you have no booster did you change the MC?
Just forgot which one that is used. It has a bigger bore.

 

[Tom H]

Chuck, Yes, he is using an F10 Dual Master.

Mike, I assume you connected the system diagonally , one cyl does front right and left rear and other master does opposite.

67 survivor, how would you connect a booster into a dual master arrangement

Group, would it make sense to use a booster connected to the front brakes and then connect the second master cylinder to the rears direct without booster?

Tom

 

[Chuck Ingram]

Chuck, Yes, he is using an F10 Dual Master.

Mike, I assume you connected the system diagonally , one cyl does front right and left rear and other master does opposite.

67 survivor, how would you connect a booster into a dual master arrangement

Group, would it make sense to use a booster connected to the front brakes and then connect the second master cylinder to the rears direct without booster?

Tom

Hi Tom

Didn't catch re F10 MC.
Not familiar but have thought about going that route. The Lister has fantastic brakes. The booster rebuild took the shop 5 times till I was happy.

 

[Mike Armstrong]

Chuck, Yes, he is using an F10 Dual Master.

Mike, I assume you connected the system diagonally , one cyl does front right and left rear and other master does opposite.


Tom

Hi Tom, no, I connected the front brakes to F, and the rear brakes to R, as is marked on the body of the master. Was that incorrect? Are dual brakes normally connected diagonally? If I re-do the brake lines to a diagonal set-up, would that cure my brake problem?

Also, that F10 brake master has a 3/4" bore, how does the bore affect breaking?

Thanks

 

[260Alpine]

Mike, Back in the day they crossed the brakes diagonally with 4 wheel drum brakes. The Nissan F and R you hooked up correctly. F is set up with no residual valve for disk brakes. R has residual valve for drum brake. The larger bore master will have a harder pedal and a smaller bore will have more travel. Usually with a booster the master will be a size bigger than the manual master. Also the pedal ratio is different, probably around 4 to 1 for power brakes and 6 to 1 for manual. So if your car originally had the power brakes that could be the issue. On the MGB, the hole in the pedal arm is 1" lower for the power brakes. The booster will work fine on just the front brakes. To improve the rear drums the series 1 and 2 have a larger bore wheel cylinder than the later series that will interchange.

 

[Mike Armstrong]

Ahh, interesting, good information Jim. So since they're interchangeable I should be able to install the earlier larger bore pistons if needed.

 

[260Alpine]

Mike, Some Tiger guys and Capri racers use Datsun 260-280Z pads on front with the stock calipers. Slightly larger and performance compounds available.

 

[Mike Armstrong]

Mike, Some Tiger guys and Capri racers use Datsun 260-280Z pads on front with the stock calipers. Slightly larger and performance compounds available.

Thanks Jim.

I know of at least one member that opted for new Capri calipers rather than rebuild his stock ones and they worked out great.

Since I've already completely rebuilt both the calipers (including stainless steel Pistons from SS) and drums, I'll probably work with what I have.

 

[Tom H]

Hi Tom, no, I connected the front brakes to F, and the rear brakes to R, as is marked on the body of the master. Was that incorrect? Are dual brakes normally connected diagonally? If I re-do the brake lines to a diagonal set-up, would that cure my brake problem?

Also, that F10 brake master has a 3/4" bore, how does the bore affect breaking?

Mike,

I guess diagonal connection is NOT correct. I guess I am still "back in the day" ! I am not at all familiar with dual systems and was just thinking about the implications of your installation.

Regarding bore diameter, understand that the bore of the master and the bore of the slave create a "leverage" situation, analogous to a lever as if you were lifting a rock with a lever, except that the action seems "reversed" regarding the bore. With a lever and a rock, you want the long end of the lever to push on, for lifting advantage. But in hydraulics, it's actually a SMALLER bore in the master that gives you more leverage for pressure from your foot.

I think the original master in a SV is 7/8" so your F10 master with smaller, 3/4" bore should result in easier pedal action than the original, partially making up for the loss of help from the booster.

I do not fully understand how the dual systems work, but I am puzzled about your experience. The whole point of the dual system is that if one half fails you still have some braking capability. In an Alpine I think about 75% of the stopping power comes from the front tires and brakes. So if you are having problems with the rear brake adjustment or bleeding, you should still have a pretty solid braking capability at the front. Maybe it makes sense to install the booster and connect it to the front brakes.
Tom

 

[67Survivor]

"67 survivor, how would you connect a booster into a dual master arrangement

Group, would it make sense to use a booster connected to the front brakes and then connect the second master cylinder to the rears direct without booster?"

I missed the dual master portion. I have no booster on my car ATM, but I have the 5" Lockheed coming from VB. Or at least I did. UPS destroyed the one package and lost the other..... But when it arrives, I will be installing it with what appears to be the original Girling master. The only markings on it are (I think) .825? Anyways, I will definitely let you guys know how the install goes and whether it makes much difference. My intention is to restore the brakes to as close to factory as possible.

Id be very leary of installing a booster on a dual master because it may apply too much force and result in an imbalance.

 

[260Alpine]

Some MGB roadsters have added a booster to the front on a dual master but have added the larger rear wheel cylinders from a GT. It won't affect balance, just make the pedal easier to push. I think if you measure the brake pedal arm from pivot on top to pedal the early series cars had longer distance or the hole for the pushrod lower above the pivot. Most manual brakes have around 6 to 1 ratio and power brakes around 4 to 1. The early series also used a smaller .700 master while the later used a .825 master. I am not a fan of the booster /servo in any case because of added complexity and additional failure point. The 5" booster would add about 1.7 X to the ratio.

 

[Mike Armstrong]

Mike,

I guess diagonal connection is NOT correct. I guess I am still "back in the day" ! I am not at all familiar with dual systems and was just thinking about the implications of your installation.

Regarding bore diameter, understand that the bore of the master and the bore of the slave create a "leverage" situation, analogous to a lever as if you were lifting a rock with a lever, except that the action seems "reversed" regarding the bore. With a lever and a rock, you want the long end of the lever to push on, for lifting advantage. But in hydraulics, it's actually a SMALLER bore in the master that gives you more leverage for pressure from your foot.

I think the original master in a SV is 7/8" so your F10 master with smaller, 3/4" bore should result in easier pedal action than the original, partially making up for the loss of help from the booster.

I do not fully understand how the dual systems work, but I am puzzled about your experience. The whole point of the dual system is that if one half fails you still have some braking capability. In an Alpine I think about 75% of the stopping power comes from the front tires and brakes. So if you are having problems with the rear brake adjustment or bleeding, you should still have a pretty solid braking capability at the front. Maybe it makes sense to install the booster and connect it to the front brakes.
Tom

Thanks for the explanation Tom.

I'll be out in the garage today. I read somewhere, maybe on these forums, that the brakes have to be adjusted 'first' before a proper bleeding should be done,? Anyhow, I'll get into the drums and adjust them out. Adjust the emergency brake cable, then use the power bleeder to make sure there is no air in the system. Report back later.......

 

[65beam]

brakes

starting in 1968 rootes went to a Lockheed dual master with booster working on the front brakes only.

 

[260Alpine]

Mike, Anything new on your brakes?

 

[Mike Armstrong]

Hi buddy. Yup.

1) I took the drums off first took take a look. The drivers side drum had black/grayish looking grease on the inside making the friction surfaces slick. Not sure where it came from, probably the cylinder. I had a tough time getting the piston out, replacing the O ring then getting it back in, must have used a bit more grease/lube spray than I thought, I think the excess got sqeezed out during operation, or, the piston isn't sealing and brake fluid is passing by and into the drum.

2) The drivers side drum needed adjusting, too loose. Tightened it up using the star wheel.

3) Way too much slack in the emergency brake cable. Tightened that up too.

4) Used the power bleeder, worked great. Can't say I saw allot of air passing out the bleeders but the whole system is definitely bled clear now.

Had to leave before taking it for a test drive.

QUESTION: Does the brake pedal arm (and maybe the clutch pedal arm too) normally have a 'return spring' attached that pulls the pedal arm back towards the driver to maintain full pedal arm movement? I seem to remember one being there that isn't now.

 

[260Alpine]

Mike, Cool! I bet they are a lot better. Should be a return spring on top of both pedals.

 

[Mike Armstrong]

Should be a return spring on top of both pedals.

I kinda thought so but I don't have any springs left in the parts box after having taken the brakes apart years ago.

I'll see if I can find a pic of the spring size and placement.

 

[260Alpine]

The Alpine might have used springs from the master cylinders stock. You may have to drill the pedal arm and attach like most other cars.