Chattanooga, TN61 posts · joined Nov 20251934 Ford pickup, SBC, Wilwood discs
34 Ford pickup, SBC, i just did a drum-to-disc conversion up front and put a new master on, and the pedal is firm but too high and grabby, and i want to get the proportioning right before i trust it on a canyon. this is the firm-pedal thread, post your valving.
setup is Wilwood front discs, kept the drums out back for now, a dual master with no booster because it is a light truck and i wanted manual brakes, and a knob-style proportioning valve on the rear. the front bites way before the rear does anything, which i know is partly discs-versus-drums, but i want to understand what the proportioning valve and a residual valve are each doing before i just crank the knob.
pro_touring_buildRoad worthy#2
Lincoln, NE74 posts · joined Nov 20251967 Camaro pro-touring, LS3, coilovers
three separate things are fighting in your pedal and people blur them. the proportioning valve limits rear pressure so the rear does not lock first, you want that. a residual pressure valve, 2 pound for drums and 10 pound for drums that are below the master, keeps the drum shoes just barely out so you do not have a long pedal, and you need one on that rear drum circuit or your pedal travels forever. and manual brakes with no booster need the right pedal ratio, around 6 to 1, or they feel exactly like what you are describing, high and grabby and heavy.
check your pedal ratio first. a lot of manual-brake hot rods are running a pedal that was designed for a booster, and no proportioning valve on earth fixes a bad ratio.
brake_master_checkOPRoad worthy#3
Chattanooga, TN61 posts · joined Nov 20251934 Ford pickup, SBC, Wilwood discs
pedal ratio, i did not even measure it, i assumed the kit pedal was right. going under the dash this weekend with a tape measure. that would explain the heavy part.
assembled_title_helpFired up#4
Reno, NV44 posts · joined Nov 20251933 Ford coupe, SBC 350, built from a kit
when you get it dialed, write the actual part numbers and the pedal ratio down somewhere, because when you go to insure and register this as an assembled vehicle in some states the inspector asks about the brake system and a scribbled answer looks bad. not every state, but mine does. a one-page build sheet with the brake parts on it has gotten me through two VIN inspections without a headache.
brake_master_checkOPRoad worthy#5
Chattanooga, TN61 posts · joined Nov 20251934 Ford pickup, SBC, Wilwood discs
pro_touring_build wrotea lot of manual-brake hot rods are running a pedal that was designed for a booster
that was it. pedal ratio was about 4.5 to 1, a booster pedal. swapped the pedal arm for a manual one at 6.2 to 1 and the brakes went from grabby and heavy to firm and progressive, and now i can actually feel the rear. added a 10 pound residual to the drum circuit and the low pedal went away. the proportioning knob finally does something gradual instead of all-or-nothing.
Wilwood has a tech section that lays out residual valves, pedal ratio and master sizing better than i just did, it is at wilwood.com and reading it would have saved me a month of thinking the master was bad.
mod_wade_hModerator#6
Loveland, CO71 posts · joined Nov 20251931 Ford Model A coupe, flathead, juice brakes
this is the thread i will be linking every time somebody says their new brakes feel wrong, because it is almost always the pedal ratio or a missing residual valve and almost never the master, and people replace the master twice before they measure the pedal. pinned in my head if not on the board.
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