How does brake fluid work?
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From: Socal
How does brake fluid work?
Yeah I know this is a very newb question. But I wanna know how it works.
I already seached + hit up the whole http://www.howstuffworks.com website. I didn't find anything helpful. Help a newb out please, thanks
I already seached + hit up the whole http://www.howstuffworks.com website. I didn't find anything helpful. Help a newb out please, thanks
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From: San Antonio, Texas, USA
Re: (THEINTEGRATION)
Why do you need to know how brake fluid works? Sorry for answering your question with a question. Well, in a brake system brake fluid is pressurized by the booster and master cyl. That pressurized fluid then pushes the caliper pistons out, causing a contact of the pads to the disks. Brake fluid is a high silicone petrolium. Like all liquids, it does not compress therefore creating pressure. Brake fluid also works to take off the paint of any persons car who has wronged you in the past (so I heard )
)
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Re: (tekracer)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tekracer »</TD></TR><TR><TD CLASS="quote">Why do you need to know how brake fluid works? Sorry for answering your question with a question. Well, in a brake system brake fluid is pressurized by the booster and master cyl. That pressurized fluid then pushes the caliper pistons out, causing a contact of the pads to the disks. Brake fluid is a high silicone petrolium. Like all liquids, it does not compress therefore creating pressure. Brake fluid also works to take off the paint of any persons car who has wronged you in the past (so I heard )</TD></TR></TABLE>
I'm just one of those people that enjoys having random knowledge especially in something I have passion for: cars. And thanks a lot for that explanation! And since I love my car and pretty much all cars I want to know how everything on it works.
What about different brake fluid types? like does DOT4 or 5 fluid produce more pressure than lower numbered ones? And stuff like thermal expansion, does it affect how the car brakes and reacts when it's heated up from continuous hard use (like on track).
I just put in some weird pads and generic fluid for my ITR recently cause the stock stuff wore out. Of course the crap on it is temporary I just needed a quick and local solution at that moment. (Acura TL Type S pads and some crap at Autozone that said it out performs DOT 3 and 4 fluids) I think the pedal feel is a bit more mushy and the response is not as...err what is the word...it just doesn't feel like it stops as well with the same amount of pressure i put on the brake pedal than on stock ITR pads and Honda brake fluid. I just plain don't like the way luxury cars feel when I'm braking with them.
Edit: I'm an inquisitive young grasshopper
)</TD></TR></TABLE>I'm just one of those people that enjoys having random knowledge especially in something I have passion for: cars. And thanks a lot for that explanation! And since I love my car and pretty much all cars I want to know how everything on it works.
What about different brake fluid types? like does DOT4 or 5 fluid produce more pressure than lower numbered ones? And stuff like thermal expansion, does it affect how the car brakes and reacts when it's heated up from continuous hard use (like on track).
I just put in some weird pads and generic fluid for my ITR recently cause the stock stuff wore out. Of course the crap on it is temporary I just needed a quick and local solution at that moment. (Acura TL Type S pads and some crap at Autozone that said it out performs DOT 3 and 4 fluids) I think the pedal feel is a bit more mushy and the response is not as...err what is the word...it just doesn't feel like it stops as well with the same amount of pressure i put on the brake pedal than on stock ITR pads and Honda brake fluid. I just plain don't like the way luxury cars feel when I'm braking with them.
Edit: I'm an inquisitive young grasshopper
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Re: (speedymon)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by speedymon »</TD></TR><TR><TD CLASS="quote">If it has a mushy feel you might have air in the lines.</TD></TR></TABLE>
uh oh...looks like i have some more bleeding to do
uh oh...looks like i have some more bleeding to do
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Re: (THEINTEGRATION)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by THEINTEGRATION »</TD></TR><TR><TD CLASS="quote">I'm just one of those people that enjoys having random knowledge...</TD></TR></TABLE>
Most brake fluids are poly-glycol. I thought only DOT 5 fluids have silicone in them, but ???
The DOT specs give requirements for physical properties, especially wet & dry boiling points. The DOT specs also say how much water to put in when measuring the wet boiling point. The boiling points are higher for DOT4, compared to DOT3. I don't know what happed to DOT1 & DOT2, it seemed like they were already gone when I was a kid starting to work on cars.
Water mixes completely with poly-glycol, which is why the boiling point doesn't suddenly drop to 212 F with a tiny bit of water. Next time you bleed brakes, pour the old fluid into a bucket of water. It doesn't float like normal oil.
There's probably some trade-offs. DOT 4 has higher boiling points, but I guess many types pick up water faster?? So if use it, you should be more careful about changing it on schedule.
DOT 5 is the silicone stuff that you shouldn't use in normal brakes. But DOT 5.1 is poly-glycol again...
You asked about developing pressure. The fluid can't influence that. It's all about the diameters of the MC pistons. Some fluids have better or worse lubricating properties for the piston seals, but that doesn't exactly influence pressure.
Thermal expansion doesn't really hurt you in brakes. The MC & calipers themselves have thermal expansion too. As the brakes heat up the fluid-filled space in the caliper gets bigger. But the fluid expands too, so it partially cancels each other out. But when your foot is off the brake pedal, the fluid pressure equalizes to the reservoir anyway so it doesn't matter.
Mushy brakes come from a bunch of different reasons. The fluid isn't completely incompressible, & the hardware isn't completely rigid either. You'll feel some combination of brake pedal flex, hose dilation, fluid compression, & caliper flex. You also have compression in the friction material of the pad. Your old pads were worn out, so they didn't have very much compressible material left. They probably felt harder than they did when new, but that was gradual so you didn't notice it.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by speedymon »</TD></TR><TR><TD CLASS="quote">If it has a mushy feel you might have air in the lines.</TD></TR></TABLE>This is more important than any of the BS I just wrote...
Most brake fluids are poly-glycol. I thought only DOT 5 fluids have silicone in them, but ???
The DOT specs give requirements for physical properties, especially wet & dry boiling points. The DOT specs also say how much water to put in when measuring the wet boiling point. The boiling points are higher for DOT4, compared to DOT3. I don't know what happed to DOT1 & DOT2, it seemed like they were already gone when I was a kid starting to work on cars.
Water mixes completely with poly-glycol, which is why the boiling point doesn't suddenly drop to 212 F with a tiny bit of water. Next time you bleed brakes, pour the old fluid into a bucket of water. It doesn't float like normal oil.
There's probably some trade-offs. DOT 4 has higher boiling points, but I guess many types pick up water faster?? So if use it, you should be more careful about changing it on schedule.
DOT 5 is the silicone stuff that you shouldn't use in normal brakes. But DOT 5.1 is poly-glycol again...
You asked about developing pressure. The fluid can't influence that. It's all about the diameters of the MC pistons. Some fluids have better or worse lubricating properties for the piston seals, but that doesn't exactly influence pressure.
Thermal expansion doesn't really hurt you in brakes. The MC & calipers themselves have thermal expansion too. As the brakes heat up the fluid-filled space in the caliper gets bigger. But the fluid expands too, so it partially cancels each other out. But when your foot is off the brake pedal, the fluid pressure equalizes to the reservoir anyway so it doesn't matter.
Mushy brakes come from a bunch of different reasons. The fluid isn't completely incompressible, & the hardware isn't completely rigid either. You'll feel some combination of brake pedal flex, hose dilation, fluid compression, & caliper flex. You also have compression in the friction material of the pad. Your old pads were worn out, so they didn't have very much compressible material left. They probably felt harder than they did when new, but that was gradual so you didn't notice it.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by speedymon »</TD></TR><TR><TD CLASS="quote">If it has a mushy feel you might have air in the lines.</TD></TR></TABLE>This is more important than any of the BS I just wrote...
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From: Charlotte, NC
Re: (JimBlake)
Great info, JimBlake!
DOT 5 fluid, in addition to allowing the water that it doesn't absorb to boil and cause your brakes to fail, also lets the water rust the lines and calipers. I'm not a big fan of silicone fluid, in case you can't tell.
I found some really good info on brake fluid, but can't seem to find it now. I'll post it if I can find it.
DOT 5 fluid, in addition to allowing the water that it doesn't absorb to boil and cause your brakes to fail, also lets the water rust the lines and calipers. I'm not a big fan of silicone fluid, in case you can't tell.
I found some really good info on brake fluid, but can't seem to find it now. I'll post it if I can find it.
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Re: (drdisco69)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by drdisco69 »</TD></TR><TR><TD CLASS="quote">DOT 5 fluid, in addition to allowing the water that it doesn't absorb to boil and cause your brakes to fail, also lets the water rust the lines and calipers. I'm not a big fan of silicone fluid, in case you can't tell.</TD></TR></TABLE>Yeah, I forgot that. DOT 5 has a super high boiling point, but you have to keep water out. If you bleed the brakes every week, before each race, then maybe it's what you want. That's not for me..
But even then, maybe you have to get different seals because I've heard the rubber that Honda uses in MC & calipers doesn't handle DOT 5 very well.
But even then, maybe you have to get different seals because I've heard the rubber that Honda uses in MC & calipers doesn't handle DOT 5 very well.
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Re: (JimBlake)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake »</TD></TR><TR><TD CLASS="quote">the rubber that Honda uses in MC & calipers doesn't handle DOT 5 very well.</TD></TR></TABLE>
I've heard that too, something about swelling and bursting and things... sounds like fun...
My buddy put DOT 5 in his race CRX, and kept it pretty well bled. He came in after a race, sat in the car for 5 minutes waiting for weigh-in, and when he went to hit the pedal, there was nothing.
to silicone fluid (in brakes that is... )
I've heard that too, something about swelling and bursting and things... sounds like fun...
My buddy put DOT 5 in his race CRX, and kept it pretty well bled. He came in after a race, sat in the car for 5 minutes waiting for weigh-in, and when he went to hit the pedal, there was nothing.
to silicone fluid (in brakes that is... )
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Re: (drdisco69)
I see some people were talking about thermal expansion so i just wanted to add something. I am a pilot and as a pilot i have toknow about the a/c systems ex. landing gear. the landing gear uses hydrolic pressure to come up and a little + gravity to go down. this gear uses a thermal relief valve so that when the gear is put up (1800psi) and the a/c flys from 30,000' where the temp. is below freezing and then the a/c decends to 1000' in fl. where the temp. is 90 F this fluid will expand. This expansion would destroy the lines if the valve wasn't used. I dono if our brakes have any way of releaving this pressure due to heat but i just wanted to add this for people that just want to know more. if i was incomplete with my explanation or you want to know more pm me.
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From: Charlotte, NC
Re: (incredteg3)
I agree that there is thermal expansion in the parts, but since there's so many moving parts, such as 4 calipers and a master cylinder, there's enough space to take up the volume. The temperature difference between cold and hot brake fluid can be over 400*, but the thermal expansion is probably kept to a minimum. I'd be interested to know what it is for brake fluid, and whether it's different from one fluid to the next.
I would also say that the expansion that goes on in the aircraft also has something to do with the pressure difference at 30,000', in addition to the temperature difference at those altitudes. I'd like to hear more about this, however.
I would also say that the expansion that goes on in the aircraft also has something to do with the pressure difference at 30,000', in addition to the temperature difference at those altitudes. I'd like to hear more about this, however.
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Re: (tekracer)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tekracer »</TD></TR><TR><TD CLASS="quote">Like all liquids, it does not compress...</TD></TR></TABLE>
no one else commented on this, so I thought I'd give a heads-up. being a liquid does not make something immune to compression. even solid material compresses/expands with heat and pressure [which are directly related, by the way]. brake fluid was designed to minimize the effects of pressure on it.
as for heat affecting braking, pads and rotors are more of a concern when being hard on the brakes.
about the airplane stuff, I find it fascinating, even tho I have no idea what you said....
I like this thread. it's like the Learning Channel on H-T.
no one else commented on this, so I thought I'd give a heads-up. being a liquid does not make something immune to compression. even solid material compresses/expands with heat and pressure [which are directly related, by the way]. brake fluid was designed to minimize the effects of pressure on it.
as for heat affecting braking, pads and rotors are more of a concern when being hard on the brakes.
about the airplane stuff, I find it fascinating, even tho I have no idea what you said....
I like this thread. it's like the Learning Channel on H-T.
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Re: (burnout289)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by burnout289 »</TD></TR><TR><TD CLASS="quote">
I like this thread. it's like the Learning Channel on H-T.</TD></TR></TABLE>
Yeah, I know, it's awesome. I feel like I've gained 1 IQ, thanks H-T uber sages ^^
I like this thread. it's like the Learning Channel on H-T.</TD></TR></TABLE>
Yeah, I know, it's awesome. I feel like I've gained 1 IQ, thanks H-T uber sages ^^
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Re: How does brake fluid work? (THEINTEGRATION)
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Re: How does brake fluid work? (Dan GSR)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Dan GSR »</TD></TR><TR><TD CLASS="quote">this wasn't helpful?
http://auto.howstuffworks.com/brake.htm</TD></TR></TABLE>
No, not really. That's the mechanics of how brakes work; I know that already. I specifically asked for how brake FLUID works. That's why I posted and got all this great help. Thanks.
http://auto.howstuffworks.com/brake.htm</TD></TR></TABLE>
No, not really. That's the mechanics of how brakes work; I know that already. I specifically asked for how brake FLUID works. That's why I posted and got all this great help. Thanks.
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Re: (incredteg3)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by incredteg3 »</TD></TR><TR><TD CLASS="quote">I am a pilot and as a pilot i have toknow about the a/c systems ex. landing gear...
This expansion would destroy the lines if the valve wasn't used. I dono if our brakes have any way of releaving this pressure due to heat but i just wanted to add this for people that just want to know more. if i was incomplete with my explanation or you want to know more pm me.</TD></TR></TABLE>
When you let your foot off the brake pedal, there's a little port in the MC that allows fluid to vent back to the reservoir. That handles thermal expansion.
I'd bet that most of us drivers can't accomplish the big changes in elevation that's typical of aircraft... (duh!) With a vented system like that you'd probably get a lot of moisture in the hydraulic fluid. So I guess there has to be a more sophisticated ($$$) way to hande expansion.
This expansion would destroy the lines if the valve wasn't used. I dono if our brakes have any way of releaving this pressure due to heat but i just wanted to add this for people that just want to know more. if i was incomplete with my explanation or you want to know more pm me.</TD></TR></TABLE>
When you let your foot off the brake pedal, there's a little port in the MC that allows fluid to vent back to the reservoir. That handles thermal expansion.
I'd bet that most of us drivers can't accomplish the big changes in elevation that's typical of aircraft... (duh!) With a vented system like that you'd probably get a lot of moisture in the hydraulic fluid. So I guess there has to be a more sophisticated ($$$) way to hande expansion.
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