Hot Rods Brake pedal ratio vs MC

Took my truck down the driveway for its first drive and just about had a heart attack when it had no brakes. '40 Ford front axle with F100 brake conversion all rebuilt, rear is '65 Mustang 8" also rebuilt. I homemade a Kugel style 90 degree under dash pedal but didnt research ratios before fab. I'm looking at 13" below the pivot and 5" above putting me at a 2.6 to 1 ratio. Not sure offhand what the MC bore is but I'm hoping that going with a smaller size one will help with my crappy ratio. With the brake assembly and cowl steering set up things are super cramped under the dash so I really dont want to do a total change. Symtoms are a rock hard pedal and tons of force required to stop from 20mph. Any thoughts or ideas? Maybe a small booster?

 

Your pedal ratio should be about 6:1.

 

... and fixing the ratio is really your only option. You can 'fine-tune' it a bit with MC size, but that won't do it in this case.

 

Smallest booster I know of is a 94 geo metro

 

No booster is going to fox a 2.6:1 pedal ratio.

 

I'm with Gimpy

 

First and foremost it depends on the amount of volume needed. Providing enough out of the master is imperative.

Now-
Dropping the MC bore down from 1" to 13/16 with that set ups pictured booster could get a livable result with a 2.6 pedal ratio.

That set up is popular with the falcon crowd because it fits. Their only complaint is the pedal effort is soft and light, in other words a little foot gives lots of brake. A logical resolution to that problem is pedal ratio that's less than the standards for power brakes.

I had a build that had a shitty pedal ratio due to modifications within stock confines and that set up worked perfectly.

 

I have a 1" bore master cylinder in my Falcon. It might even need a 1-1/8" one.

 

1 1/8 is right about the realistic limit before having to add a booster . the strange kits we use on cars we change over are 1 1/8 and they have a nice pedal feel with a disk /drum set up and a disc disc set up as long as the calipers are not to large in pot size .( d52 is the largest )

 

I have about 5/1 pedal ratio and it works OK with a 15/16 bore master. It takes effort but not bad. I don't see fixing your set up with a different master.

Gary

 

I try and shoot for a 7:1 ratio

 

On Race cars with "Poor Man's ABS" the Wilwood pedal box is common.
They have a 5.25:1 pedal ratio [ twin 3/4" master cylinders is common ]