"Rubber" brake hoses are high pressure hydraulic hoses that have layers (multiple layers) of nylon and/or metal mesh reinforcement within the hoses. They don't "give" much at all. Maximum allowable expansion during the entire service life of the hose is required to be less than 0.020" or so at 2900psi. I don't remember the exact figures, but the allowable "expansion" is very low. They also have to be tested at 4,000 psi for an extended time (several minutes) and a burst strength test at 7,000 psi for a short spike.

I know that mechanics are trained not to let calipers hang by the hoses to prevent damage, but I've seen a car slide off a forklift in a junk yard in a way that one of the brake calipers hung on the tines of the fork lift, and the entire 4 door mid sized sedan was hanging by one of the brake hoses. Even stock "rubber hoses" are really, really, really tough.
"Wet" brake fluid (brake fluid that has absorbed some moisture) is more compressible than "dry" brake fluid. After as little as 6 months, and certainly after a year or two, there is a noticeable softening of the brake pedal from moisture accumulation. After more than 2 years, it's quite significant. Again, this is most of what you feel when you "upgrade the brake hoses" to braided stainless.
You are correct, most people don't drive much on flat tires. One of the arguments of why braided stainless hoses are "better" for brake performance is often "race cars have braided stainless brake hoses." My point was that the main reason my race cars have braided steel hoses is because I want them for durability. Race cars are driven in conditions where most street cars would be parked. I want brake hoses on the race car that will get me back to the pits with a flat tire, even if I'm driving it around the rest of the lap at 60-80mph on the straights, with the shredded tire flapping around and tearing stuff up. I don't want the brake line to get torn even in those adverse circumstances. My choice of braided stainless isn't about "pedal feel," it's all about durability.

 

horse ****...

water is not any more compressible than brake fluid... both are considered incompressible as far as what little pressure brake systems are able to generate. I am sure you COULD measure the difference with some type of lab equipment, but it doesnt matter in this discussion because its not something a vehicles brake system would ever notice.

wet brake fluid lowers the boiling point of the fluid. When the fluid boils, it creates bubbles which are compressible... but the physical presence of water in the fluid does not cause the fluid itself to be any more compressible than if it was completely dry of water. As fluid ages its VERY easy to boil it as brakes under normal conditions can get into the 300-400 degree range pretty easily.

"feeling" a better brake pedal after a fluid flush is usually a placebo effect that in reality isnt there.

 

During the serviceable life is the key word. I guess where I am coming from is me and a friend had changed the hoses about the same time. He went with OE and I went with braided SS on a similar car. We both flush our brakes at the same time since he had a pressurized flush tool and I used it on the same day so he doesn't have to clean up again. Seems like his pedal had a little more give than mine did on year 6.

They are schooled to hang it off a wire or at least that was what my shop class told us. That said, I have seen them hang it off the rotor or whatever surface they can. And if you believe it never falls, I have this bridge for sale. Just walking through the shop and glancing around, at least half of them do it.

Now that I own my own bleeder and have a compressor, it is definitely every 2 years at least. Bust my butt for a couple days to get everything done (5 vehicles, 2 ATVs, 2 motorcycles) within a day or two with time to do other stuff. Only reason I believe US and a couple other cars don't, especially cheaper cars is that they don't want to scare the owners into thinking maintenance has to be done.

Fair enough. So since I flush every couple of years like MB suggests, how long before I run out of life in the hose? I wish there was some way to tell since I don't have OE hoses anymore since I'd like to see if there is more pedal travel after 5 to 10 years of using the hose vs braided SS hose.

 

IIRC, the coefficient of isothermal compressibility for brake fluid is 80 to 100 times higher for glycol based brake fluid than it is for water, meaning it takes 80 to 100 times as much force to compress brake fluid by an equal volume compared to water. The actual amount it compresses is miniscule, but water definitely compresses more under high pressure than brake fluid.

That said, I won't swear that it's the water itself that causes the longer pedal. What I can say with absolute certainty is that when I work on a higher mileage, older car with a less firm brake pedal, and I flush the system, the pedal gets more firm. There's something compressible in the system when the fluid is old and has discolored to the point where it's the color of Coca-Cola. It could be the water in the system, but it could also be some other by-product of aging and corrosion within the system.

So, after 6 years you compared the two, and you're certain that you flushed your own fluid (with the braided stainless lines) every two years, possibly more often than that. Are you comparing braided stainless lines with 2 year old fluid to rubber lines with 6 year old fluid? I would expect older fluid to make a softer pedal. That's been my experience.

As for "service life," my experience with standard (stock, rubber) brake hoses is that they last about 10 years before I find them stiff and/or cracking and needing replacement. Honestly, on the race cars, I don't think I've had any last as long as 10 years. Usually they get damaged before that point, or I've sold the car by that age. I will say that the service life of teflon hoses is not infinite, and I doubt the service life is any longer than standard (stock, rubber) hoses. I would also say that the teflon inner liner on the braided hose is what will eventually crack or harden and fail, and it's tougher to inspect that than it is to inspect a rubber hose which will likely form cracking on the outer surfaces as well as the inner.

 

We both did regular flushes at the same time so he has fluid as fresh as mine since we shared the flusher. Only difference in our cars is that he has regular hose and I had SS braided hose. After 6 years, it felt like he had a little more pedal travel than I did. We were also changing pads since it was pretty close to the sensor and when we changed pads we would open the bleeder screw, use the C-clamp and retract the piston. At this point, we bought a pair of pads and decided to just flush and do pads since we were already getting dirty. I thought he had a little more travel so I used a stick and marked max depression. IIRC, it was about a quarter inch to half inch difference, maybe? Since pads were just changed and fluid was also flushed, I didn't know what else it could be.

IDK. Maybe I should just toss them at 10 years even if they are braided SS lines with teflon insides.

 

I replaced all four with Russell. Can be found at Summit Racing and Advance Auto Parts.

 

Well, it sounds like a fair comparison, @aklim.

And I should be clear that I wasn't saying that there is no difference in "pedal feel" between braided stainless and stock brake hoses. I was saying that overall, for most people, the improvement from fresh fluid is far more significant than the minor change in pedal feel from braided stainless hoses.

Even the StopTch page that someone linked to above (http://www.stoptech.com/technical-su...rake-lines-q-a ) lists as the primary (meaning first listed) advantage "1. The SS braid provides superior protection from flying roadway debris. "

Personally, I wouldn't trust any flexible brake hose past 10 years, and I'd start inspecting closely at about 6 years, looking for cracks or a loss of flexibility. "crunchy" brake hoses are past their useful service life.

One more thing about braided stainless hoses, if the braided metal is exposed, you want to be certain that your retainers/hose holders are strong and well fixed to the hose and the body work or whatever. Braided stainless steel hoses are highly effective "files" or "saw blades." If they can move relative to whatever they are in direct contact with, they will file, grind and saw their way through almost any other material. Don't ask me how I know this.

 

Additionally, some of the problems blamed on calipers are actually the fault of a degraded flex line, whether it is braided or oem style rubber. Once they go bad, you can put the brakes on, but as they collapse internally, they don't let the fluid relieve the pressure after the pedal is released, causing the brakes to "drag" on the failing side(s).