Long story short...I changed my "under the car" 7 inch booster and MC... Went to a dual diaphragm...found some improvement there... I want to try to get a little more out of them tho... Because it is power brakes, the MC is a 1-1/8" bore... As we all know...a 1" bore (non power brakes) requires less pedal input for equal results... 1...Does anybody here know HOW MUCH better a 1" bore would feel than 1-1/8" bore...? 2...One thing I realize is that the larger bore MC is a shallow hole and the smaller bore MC is a deeper hole...almost 1-1/2" deeper...because they are to be bolted to a booster instead of brake pedal linkage... So...I would ***ume that one would need a longer push rod coming out of the booster to accommodate the smaller bore MC because of the deeper hole...correct?
This is not an option to explore. Your booster needs to be since the flat portion of the piston compared to the tip of the rod. If you get it wrong, the brakes will function in very odd and unsafe way's, like full lock up with little to no effort. I know, it wasn't funny when I got the key's to the Family Daily thrown back at me with the word's, "Are you F@%&'n trying to Kill Me"
You need to find a shallow bore master cylinder that is 1 1/16" bore. Also what brakes are you using? Disc/drum, drum/drum, do you have residual valves in the lines, what size are the calipers, etc? Let us know what the entire system consists of so we can help.
As far as it being dangerous...last night I researched and it is VERY common... In fact some deep MCs come with a "bullet" in them to be used either way... Also you can buy the longer rods for the booster from Summit etc... I am not one bit concerned about that part of it... Thank you
I have a 95 Ford Explorer rear end with the stock disc brakes... GM metrics on the front... 2 LB residual valves on the way... Thank you
I guess my question really is this... How much difference is the pedal feel between a 1" bore and a 1-1/8" bore MC...? Is it worth the change...?
In an unboosted system, you would notice the difference in effort between the two bore sizes. How much that difference would be is dependent on various other system factors. Whether it was "worth it" is a subjective judgment. Ray
I've changed out several 1" bores for an 1 1/8' bore. Not much difference in pedal pressure, especially with a booster. A 1' bore requires more pedal travel, in a lot of under floor applications that extra travel puts the pedal uncomfortably close to the floor while braking, if one system failed I'm afraid the pedal would bottom before it stops, eliminating the purpose of the duel cylinder.
Ya...that's kinda what I was thinkin too metalman...according to what I have read doing research... Thanx to all!
Pedal effort varies directly with the area of the cylinder. The larger the m/c bore, the more pedal effort required, and vice versa. The area varies as the square of the bore diameter. To compare the ratio of area of two circles is easy if you make both of them fractions with the same denominator. 1 1/8 = 9/8 and 1" = 8/8 Just multiply the top number of each fraction by itself and you have the two numbers to compare. 9 x 9 = 81 and 8 x 8 = 64 Ratio of pedal effort for the smaller cylinder versus the larger is 64/81. Divide it out and you get 0.79 or 79%. About 20% less pedal effort with the smaller cylinder. The travel at the master cylinder will be the opposite ratio, or 81/64, so there's about 25% more travel at the m/c. Keep in mind you have to take any increase in the active travel of the m/c (the portion of travel where the piston is moving fluid, and not the portion that's slack or clearance) and multiply it by the pedal ratio to get an idea of how much further the pedal is going to travel.
Don't we go through master cylinder size at least twice a month? I am not sure what you are wanting out of your brakes that you don't already have? I am not saying that to be mean I just don't understand what you mean when you say you want a little more out of them. they are not stopping the car or it is too hard to push the peddle or???
Just always trying to improve things and this time it happened to be my brakes... Ya...they are ok and they DO stop my car but are they as good as brakes that I have had in the past...probably not...probably due to the tiny 7" booster... Everything is good now...thanx to you guys I have all of the info that I needed to confirm my thoughts on it
If you change booster size or even from manual to power ***ist your peddle feel is going to change. I go by this simple rule that a road race builder once told me, if the brakes lock up you got too much brake and they are not stopping the car when they are locked up. I was never a "road racer" but I figured he must have some idea, his cars were winning.
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