Technical Brake pedal ratio issues

I have a 58 Ford Courier Sedan Delivery and have been battling brake pedal issues for a long time and I have decided to tackle it again. Front disc conversion from a 68 LTD. 11" with 2 3/4" bore calipers. Stock rear drums with 15/16" cylinders. I had a single 11 inch booster on it and it would stop on a dime but the pedal went almost to the floor. I determined that it was the pedal ratio and no way to modify the pedal. Ditched the booster and I have plenty of pedal but it pushes hard. I have tried 3 different bore MCs, going smaller but it still does not stop good. I want to put a booster back on, but have since went from a small block to an FE, so booster/valve cover clearance might be interesting. I am looking at a conversion from Jegs for a Ford pickup. I will try to attach a link. It appears that the bracket and linkage in this kit corrects that pedal ratio but I called them and the tech said he didn't think so. It also looks like the bracket would raise the booster up a couple inches which might help my engine clearance. I am on a budget and don't want to spend a ton on custom setups. I thought about getting smaller diameter calipers but these LTD spindles are really odd and nothing will bolt to them. If anyone would have any tips, I would appreciate it. Here is a link to that kit: https://www.jegs.com/i/JEGS+Perform...zUscbv_87gjHubGCcl_W6LG8UwWOGv0AaAm6IEALw_wcB

 

What pedal ratio do you have? For manual you need 6+ :1. Even if you're going boosted you need to know the ratio.

Chris

 

The car is in storage and we are expecting a foot+ of snow, but I checked it last year and IIRC it was 6:1. But I want to put a booster back on it so I need a system that changes that ratio with the linkage/bellcrank.

 

I found these to be helpful reading:

https://www.speedwaymotors.com/the-toolbox/changing-bore-size-on-a-master-cylinder/30895

https://www.joesracing.com/master-cylinder-math/

 

The second link made my brain ache,,lol. The Speedway one was helpful though. I will have to do some measuring but maybe I am just a master cylinder (bore size) swap away from making it work. Thanks!

 

How about going to hydraboost , might help w space ?

 

That picture from Jegs bothers me a bit. That set up looks a lot like the generic booster/master/pedal assembly made by the Hoffman group. Those set ups were junk. The small diameter boosters don't work worth a darned, the pedal swing binds up, and the whole mess equaled a hard to push pedal on my son's 57 Dodge wagon. They say the dual diaphragm boosters work better, but I know the single diaphragm ones are worthless.

If you go to the Wilwood web site and provide the diameters of your calipers and wheel cylinders, and your pedal ratio, they will calculate what diameter master cylinder you need, with or without a booster. Of course they will want to sell you their stuff, and will also provide their part numbers.

Were you looking at the "kit" from Jegs because you need the pedal assembly, or simply because it was a kit that is suppose to have everything you need?

 

With the booster set up that worked but went to the floor, was the brake pedal resting high or could you raise it with a longer push rod from the pedal to the booster. I run into the same problem when I built my car and put up with it for a while, the longer push rod fixed the problem and didn’t raise the pedal that much.

 

Is there a eccentric bolt on pedal under dash to adjust ?

 

Years ago, when we all used junkyard parts, I used a master, booster and pedal assembly from a Chrysler Cordoba on a project. The pedal assembly had a linkage built into it and I don't remember if it increased leverage or stroke. It was a pretty short arm so it probably increased leverage, but Im not sure.

Gary

 

Thanks to "in the pink" comments and links. That Speedway chart was really helpful. I think my whole problem is in the MC bore size. I checked my pedal ratio and it is 6:1. With my caliper bore size, it looks like I need an 1 1/8 MC. I will try that when I get the car out of storage. My rotors and calipers were from a power brake car so I didn't think I could get a manual pedal/MC to work with those. Thanks again to everyone! This is the greatest site ever for getting good information without people being rude or insulting!

 

1 1/8" bore master is way to big to make enough pressure without boosted assistance. I calc it at just shy of 600psi with 100lbs input. That's not stopping you unfortunately.

Chris

 

I try to always use factory matched parts when doing these swaps. If it worked at the factory, then it will work great on the swap. I'd suggest using a dual master from a late 60's or early 70's Ford truck setup for disc/drums, and also a booster for the same vehicle.
I used smaller diameter discs on my '63 Falcon and used a '69 Mustang dual disc/drum master and that car stopped extremely well even with the BBC engine, and extra weight.
If your pedal was soft or going to the floor I'd be willing to bet it wasn't because it had a power booster. More likely there was an issue with the booster, or something else causing the spongy pedal. All in good order a power booster should just make stopping easier, not make the pedal travel too far.
1:6 is a good ratio for manual brakes, while power can work at 1:5 or the same 1:6, but will be more sensitive at 1:6 ratio.

 

OK, that Speedway article was with a booster, so the 1 1/8 would be too big for manual. I had a 15/16 MC on it, stopped OK but the pedal pushed hard. Went to a 21 mm (-7/8) MC and it is softer but still doesn't stop good. With those 2 3/4 calipers in front and a 6: 1 pedal, am I going to able to get any MC to work without a booster? I would like to put power back on it, but need a setup that corrects that pedal ratio with a bell crank type system. That is why I was looking at that Jegs setup. Thanks.

 

Thanks for the info. I don't think the pickup booster would clear my valve covers or are they a dual booster? Would a 7 or 8 inch dual booster be as good or better than a bigger diameter single? I keep thinking that my big (2 3/4) calipers are part of the problem also, not being able to get the right pressure with my pedal ratio and different MCs that I have tried. I love the car but just wish the brakes were a little better. Thanks.

 

Seems like smaller front calipers might be what's needed.
Try the math with a theoretical smaller front and see the result?
Try the math with 2.5 caliper.
Then 2.25 caliper.
See what gets closer to the 15/16 master cylinder, which matches rear wheel cylinders.

 

The MC on it now is 21 MM, just under 7/8. I had a 15/16 MC on it but the pedal was too hard. The smaller one is softer but I can stand on the pedal pretty hard and it is nowhere near locking anything up. The calipers are 2 3/4 and I think the rear drum cylinders are 15/16. Pads/rotors/drums/shoes all look good and I even sanded everything last fall to take the "glaze" off them. It stops OK, but I wouldn't want to get into an emergency situation with it. I have had it jacked up and had my wife push the pedal and all 4 wheels are "actuating", so there is action going on, just seems like it should be better. When I had the booster on it years ago, it would bounce me off the steering wheel with a light touch, but the pedal was within a couple inches of the floor before it would stop. I have blamed that on the pedal ratio. I had actually put a T5 in it years ago and the clutch linkage hit the big single booster and that is the main reason I went back to manual brakes. It is an automatic again now but a big block so valve cover clearance is now an issue with a bigger booster. Thanks.

 

I haven't done the math on that yet, but was going to swap calipers last fall. After checking it out, my 68 LTD spindles have a strange mounting system for the calipers and nothing else will fit. They are so odd that I couldn't even find replacement pads for it at the time.

 

6:1 pedal should work fine with a booster. Might be a bit sensitive or 'grabby', but you can adjust to that or make further changes, but it's nice to know they will pull hard if needed. I have a 41 Chevy with dual 8" booster and 1 1/8" master and about 5.5:1 pedal and it stops great. Dunno about the calipers (they're on an unmentionable front end) and the rear is 10 bolt but I've never checked the cylinder size. The dual 8" works well, a single 7" is ineffectual, in my experience.

Chris

 

Info here indicates there is more than one caliper style for 1968 Ford Galaxie/LTD.
https://www.fordforumsonline.com/threads/1968-ltd-disc-power-brake-woes.30760/

 

Single 2.75" 1968 LTD caliper:
https://www.napaonline.com/en/p/NUG9717808A

Are these what you have?

 

Smaller caliper will result in less braking. Not generally what one is after.

 

Here is a 1968 Fairlane 2 3/8" caliper.
https://www.napaonline.com/en/p/NUG9717809A

Does it look like it would fit your spindle?

What does the math show with this caliper?

 

If your brake pads are a very hard composition , that can foul up the feel & operation of the brakes ..

 

I am rethinking my situation. I really can't understand why it doesn't stop better than it does. I have a 6:1 pedal ratio, 7/8" master cylinder (21mm actually), 2 3/4 front caliper pistons and 15/16" rear cylinders. The pads/rotor/shoes/drums look good and I sanded all of that last fall to take off any glaze. But those pads and shoes are 25 years old with around 40K miles on them. They look almost new probably because I drive like the old geezer that I am. But, maybe the pads and shoes just don't have grip anymore? The pads are odd and unavailable after a quick search. I'm sure rear shoes won't be a problem and those pads must be available somewhere. I know all 4 wheels are applying when I step on the pedal and it does stop OK, but I have stood on them as hard as I can on the blacktop and nothing locks up. I know locking them doesn't stop as good as not, but they should still be able to. Maybe before trying to retrofit a booster, I should go with pads/shoes and turn rotors/drums.

 

I’ve never heard of pads and shoes “wearing out” just sitting there. Sure maybe they become unglued, but it they are thick and still stuck to the backer, they don’t need replacing.

I think you have a geometry or physics problem, not a worn-out problem.

 

6:1 pedal and 7/8" master should be giving 1000psi which is a decent enough number for stopping, but might have unnerving pedal travel. I don't know how that would operate with the calipers and cylinders you have, but if the pedal is not hitting the floor they must be getting the full pressure, so should operate, which I think is what your saying anyway, but you want a little better. I think there's more pressure available from your leg when your heart is in your mouth, certainly more than 'as hard as you can'! I'm feeling weaker as I age (only 65 too!) which might go some way to explaining the change. And I've never heard of pads / shoes deteriorating over time (unless separated) but they might have somehow become contaminated? Got to be worth seeking replacements.
I'm wondering if the caliper/ wheel cylinder diameters are small. I've never ventured that deeply into the math!

Chris

 

Is the brake fluid 25 years old, too? Cheap and easy to change out if so.

 

No, the fluid has been changed plenty of times. I have swapped master cylinders at least 3 times trying to get better brakes. And bled and adjusted them multiple times. We are having a major winter storm now but if/when spring returns, I will get the 58 out of storage and check it out some more.

 

I figured not, but just something to cross off the list.

I was curious, so using the math in the Speedway link I posted above, 5.94 in^2 (for 2.75" bore caliper) x .52 (for a .81" brake master cylinder bore (@highpockets is actually .82 [21/25.4 = .82677]) = a pedal ratio of...11.42

To obtain a 6:1 pedal ratio while retaining the current 2.75" bore calipers, a 1.12" (1-1/8") bore brake master cylinder would be required, according to the formula/math. I think the existing pedal ratio should probably be measured and confirmed first, but it seems like a larger bore master cylinder would be a step in the right direction.