Can someone help explain the relationship of bore size to pedal feel?
I recall that with one size, the pedal travel is longer and requires less effort while the other results in a short travel/firmer pedal?
I ask because I want to switch the power brakes on my Charger to a manual setup. I'd prefer to keep the "feel" similar. I have a 75 Dart power booster, master and front calipers. The rear has a Dr Diff disc kit with Mustang calipers. As is, the bias is perfect but the low speed vacuum results in poor braking under 10 mph. I am not interested in adding a vacuum can or anything else to crutch the power system.
I found out that my master cylinder is different than a manual version, but the parts guy couldn't provide any specs like bore sizes.
Thanks.

bigger bore requires more leg and less travel to get the same result on the slave end. smaller bore = less effort/more travel to apply the same amt of force and a hyd floor jack would be an extreme example on the small bore end. That's on paper & way back (didn't know better) I used a 1&1/8" dual M/C on a DD 65 Dart w single piston discs/10" drums & the pedal effort ain't excessive (& I'm not that strong). Though I do drive easy around town and it will lockkup the rears on a panic stop. Almost forgot the worst , I'm using the orig 4 wheel drum splitter (was in a big rush) and semi met front pads. Neither rotor or pad wear is excessive

If you want to go manual, on your 4 wheel disc set up, there are several aftermarket manufacturers making masters in the 3/4", 7/8" and 1" bore configuration, smaller bore, more travel, make sure a master has the fluid capacity to meet the calipers used, so it won't run empty on a full stroke, pedal MA (mechanical advantage) ratio may need to be increased,....I'll post the list of factory boosters if you wish to choose from that list...


FYI,...IMHO I'd stay with the power set-up, that's just me, as a comparison, my 70 Charger, 440/6 5 speed OD, cam spec .520 lift, 285 dur. and 10-12 inches of vacumm, I run a Bendix dual diaphram booster, 70 B body 1 1/8" master, factory pin type calipers up front, and a SSBC rear disc set up (Thunderbird SuperCoupe set-up basically)...and a vacumm reserve canister under the battery tray (factory set-up)...my TOTAL pedal travel is 1/2" MAXIMUM to achieve 4 wheel lock up, pedal effort is NON-EXISTENT, in fact it requires a very light touch....

Mike

.....cont.