After searching on line, It looks like everyone is using disc brakes, NOT I’m setting up ‘48 Lincoln bending brakes on a banger coupe. What kind of brake pressure should I be seeing at the wheel cylinders. Because of the difference in tire diameters, 5.50-16 front, 6.50-16 rear, do I need to change wheel cylinders. Currently setup with a 1” Wilwood master. Thanks
The stock Ford master cylinder has a 1-1/16" bore so the 1" is fine, ***ume Mercury is the same. You need a 10psi residual check valve for the drums. Is there a check valve in the Wilwood master? Brake line pressure depends on your pedal arm ratio. The lower the fraction, like 1 to 6, the easier to apply pressure but more stroke. No reason to change to different wheel cylinders.
Pressure at the wheel cylinders??? I have no idea how you could ever measure that or why. I think what you are asking is the mechanical advantage of wheel cylinder vs master cylinder bore. You also have to consider pedal ratios and the throw or stroke of the brake linkage. One problem I see with brake systems, especially dual master conversions on drum cars is, if the pedal ratio is not right, if the pedal throw is not right, only the fronts are really working... The simplest thing to do is mimic the system from the donor car. I'm going to ***ume the '48 Lincoln is a under the floor master. If so, simply using the Lincoln master (Maybe even a Ford or Mercury master 1939-1948-to 52 in F trucks) with the Lincoln wheel cylinders makes for a simple brake system on a A banger. The single pot system was dead simple. If you look at how the system works, braking is accomplished by wheel vs master bore size. Larger bores for the fronts, smaller for the rear. It's very simple. A dual pot, of course can work but the system is more complicated. Since it's a split circuit it works differently. This means proportioning valves (maybe) to get adjustment for the rear brakes. This rolls back around to pedal throw and if the rears are receiving full braking power.... Personally if I was setting up brakes for a Early Hot Rod, I would use a single pot. I would use either the 1939 Ford/F1 master or a Ansen type conversion (Early 60s Chevy Truck Swing Pedals with the firewall mount single pot Hydro Clutch and Master combo)... With the Wildwood dual pot, you have to try to mimic the donor car setup and prepare to adjust with a proportioning valve. Also with some systems residual valves are necessary especially if you go with a firewall mount master cylinder and use it under the floor. There's lot of potential tweaks to do with dual/disk type masters.
Actually pressure is quite easy to measure with a brake pressure gauge, screws in where the bleeder screw goes. And the tandem master doesn’t change anything other than plumbing IF you use one the same bore as the original single pot, then use the stock wheel cylinder and bias doesn’t change from stock. That all being said there is nothing wrong with using the single pot master either. I’ve never felt the need to “upgrade” to a tandem master, make sure the brake system is in good working order and have a functional emergency brake system and enjoy the car. Sent from my iPhone using H.A.M.B.
Read 57Fargo's brakes 101. Good explanation of this subject without being over your head complicated.
I put a dual chamber master cylinder on my 48 Ford Sedan. Of co****, I chose to leave all the tubing and br*** valving **** off the ***embly. The results are, when you open the bleeder at the wheel, the pedal goes to the floor. So much for the safety of a dual chamber. If I had to do it again, I would use a 65 Mustang type single pot.
I want to know How much your Car weight's when I had my Lincoln it had Disk in front & Drum in rear the car was 5000 lbs., & it came that way from the Factory. ( 1971 ) mark 111, hp 365 My Merc in my avatar has a Sbc it it and I am running the Stock Drum Brakes all the way around the merc is (3500 lbs.) 300 hp My Drum brakes Stop very very Good . Just my 3.5 cents Live Learn & Die a Fool
I forgot to tell you that when I was Racing I had a 3430 lb.car with a L-88 putting out 850 hp. & I ran Drum Brakes all the way around and it Stopped the Car So it depends on a lot of things Why you want to use Disk Brakes .! Just my 3.5 cents Live Learn & Die a Fool
Stock wheel Lincoln cylinders were 1-1/8. But; from past experiences with skinny hot rod front tires a step down in size to 1-1/16" cylinders is where I would start. Of course, your cir***stances may be different. 1-1/8" wheel cylinders = WC18290 & WC18291 1-1/16" wheel cylinders = WC9090 & WC9091
There’s something wrong, remember you will have greatly increased pedal travel but should still have half the brakes function, now if you only have rear brakes it won’t be much, the front does 80-85% of the braking. Sent from my iPhone using H.A.M.B.
That still beats having no brakes with a single piston master cylinder when a line or wheel cylinder blows and ****ping your pants while you figure out how the hell you are going to miss the rig in front of you and get stopped. I've had it happen both ways and having less than half a set of brakes beats the hell out of having no brakes in busy 30 mph traffic and hoping that you can miss the rear bumper of the car in front of you and miss the car parked at the curb and make it around the corner on the side street where you have room to stop and collect your sanity and figure out what the next step is. My first go at that was when I was 17 and my 55 Metropolitan rag top only got a scratch on the right rear quarter from and early 50's Chevy's bumper bolt and left a bit of green paint on the bumper bolt. Luckily I didn't need a laundry change but came close.
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