Putting a power booster on a 40 ford pickup. It has the 11 inch disc brake setup in front with GM calipers and a ‘74 bronco rear 9 inch with stock drum brakes. 1” or 1 1/8 inch bore? I would think the 1 1/8 for the disc/drum setup but curious what you guys did or think?
You need to look at pedal ratio, pedal travel, and the drum cylinders too. I started with a 1 1/8” bore, on a power booster. Too little pedal travel to activate the booster, but rock hard pedal. Going down to 1” gained me pedal travel, enough to get the booster to kick in, and better braking.
Before selecting a master cylinder, do you understand brake pedal ratio for manual vs power brakes? https://techtalk.mpbrakes.com/how-to-series/correctly-calculating-pedal-ratio
yes I understand the ratio. I am only asking because a gentleman told me to run the 1 1/8 because that is what he has in his stock 1977 bronco with front disc brakes. Not sure of the size of 1977 bronco disc brakes.
Just doing shakedown on a Tudor that I did with disc/drum, a 7” single diaphragm booster and 1” bore master cylinder under the floor with a 6:1 ratio pedal. First one I’ve done with a booster, but it seems to work really well.
DON'T...NEEED a big ol ugly, heavy, "booster" if the correct parts are chosen. Front caliper piston diameters (total piston sq.in.) vs. the rear caliper piston diameters (total piston sq.in.) vs. the pedal ratio. A few books to learn from on the subject on the book shelves. Mike
My general rule of thumb is to do some research into what size master cylinder the "donor" of said calipers and wheel cylinders ran from the factory.
You need lots more details here. 1977 Bronco (stock) caliper at OReilly You don’t say what “GM” calipers you’re using. Regular or “metric”? Originally installed on? Here’s 1977 Nova calipers Notice the piston diameter is different. So what’s working on a stock Bronco has no bearing on whatever you’re building here. I would not trust any brake advice from this gentleman, he’s not even asking the right questions first.
Calipers on the front are 71-77 caprice. 11 3/4 ford rotors. Spoke to a tech at speedway today and they suggested a 1” bore for what I have.
The Jalopy Journal
