Re: Increasing front brake hose size opinions
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Line size doesn't matter... it's the piston size on each end of the line.
I think they use small lines because then they can get more fluid displacement and get fluid out of the hot caliper. I could just be imagining this too.
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Tube & hose size does matter, a LOT! In steel tubing there is almost 2.5 square inches more surface area per
foot with -4 or 1/4" tubing over -3 or 3/16" tubing. It is nearly 1/3 of another front caliper piston's area. That's a lot more surface area that will deflect. Deflection = mushy pedal. Put your hand on your rubber brakes hose and have a buddy stand on the brake pedal. That should show you that small is good. Going too far and trying 1/8 will not flow enough and cause a delay in brake application.
Don't use -4 for brakes in passenger vehicles, it's OK for hyd clutches. Bigger trucks, like 5 tons, use 1/4" hoses b/c of the large wheel cylinder volume.
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I didn't write the first part so I don't know what the f' you were thinking.
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I picked both of the bad sets of info and compiled them. Didn't mean to infer that you wrote any or all of that.
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Hose
diameter only matters outside of reason. It's the length of the hose that matters more. If your hard lines expand any noteworthy amount you have issues. If you're using crappy hoses (such as most cheap wannabe stainless braided ones) then get some stock ones.
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No, yes, and yes. It is the total surface area in the system that is important. Diameter and distance be danged, although they are what determines the surface area of the conduit. You want the lowest ratio of non-working surface area to working surface area that you can get, w/o crossing over into such a small tube size that you can't move the needed volume.
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The slave cylinder moves a set distance...
The amount of fluid needed to move that set distance doesn't change...
Therefore the master cylinder need not move any more fluid...
The only thing that changes is that the fluid in the line physically moves less distance...
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That ignores the not quite insignificant amount that the steel hardline will grow under pressure. Steel hardline grows under pressure at about the same rate as -3 braided stainless hose does. That growth shows up as lost motion or mushiness at the pedal.
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It seems like in my readings years ago I read that brake hose specifications were based on increase in volume per unit pressure. So even though a hose might be larger in diameter it had to meet the same specifications in expansion as a smaller hose.
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Expansion is a function of area and the strength of the material(s) in question. If the expansion of a larger ID hose is to be held the same as a smaller hose the material hte large hose is made of would need to be stronger. Which it is not w/o changing types of hose. Look at what the rated service pressures are for any hyd hose as compared to the size of the hose. As each type of hose construction increases in size the max pressure decreases.
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Anyway, keep the hoses short. If I were a rich person I'd probably use Earl's Speed-seal ends and Speed-flex hose.
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Good advice. XRP is also good stuff.
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The funny part about those aeroquip or earl's ends is that they CAN'T meet DOT requirements because the ends aren't swaged or crimped on. Even though they're a superior way of fastening.
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To my knowledge there is no DOT requirement for how the hose is actually constructed. There are three performance tests in the DOT test. Braided Stainless hoses easily pass, and do better than OE type hoses in two of those tests. The third test is designed to fail braided stainless hoses which is why all of the DOT legal braided stainless hoses have some sort of strain relief around the braid right at the sleave.
From my former Design Engineer employer:
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