Brakes Overview

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Amskeptic
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Brakes Overview

Post by Amskeptic » Sun Sep 03, 2006 7:14 pm

Your engine converts potential energy stored in gasoline into kinetic energy. Your brakes convert kinetic energy into heat.
Through all of this you get from point A to point B.
We want your brakes to efficiently convert motion into heat and we want them to effectively dissipate the heat generated.

The hydraulic system (master cylinder, lines, and wheel cylinders or calipers) is devoted to communicating your desire to slow or stop the car to the pads (disk brakes) or shoes (drum brakes) that use friction to convert the kinetic energy of the rotating disks and drums into heat.

You are here if your hydraulics do not communicate your desires properly or if the "friction generators" do not generate friction evenly at each wheel, or perhaps they just bring too much attention to themselves by squealing. Leaky hydraulics prevent you from developing the pressures you need. Uneven friction causes swerving.

The brakes are engineered to be simple and robust. Do not fear working on them. They were designed with the mechanic in mind, meaning the engineers had to make repairs and maintenance fairly idiot-proof for liability reasons.
(to be continued)
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

Spezialist
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Post by Spezialist » Tue Apr 08, 2008 5:26 pm

When bleeding hydraulic systems it is unnecessary to remove every bubble from the system, as long as the brakes feel safe going down the road, the little bits of air will work their way out of the system over time.

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Amskeptic
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Post by Amskeptic » Tue Apr 08, 2008 7:47 pm

Spezialist wrote:When bleeding hydraulic systems it is unnecessary to remove every bubble from the system, as long as the brakes feel safe going down the road, the little bits of air will work their way out of the system over time.
I am going to qualify this. We cannot really judge how much air is left in the lines. We can only use our senses to observe or feel. If you have a bleeder line going into a bottle, you keep bleeding until you see no more bubbles and then a little more for flushing. If you have a spongy pedal, sometimes it is just the booster valve for those with power brakes, sometimes it is flex in the hoses and drums and shoe webs.

But as a matter of principle, you want the very most efficient transmittal of your leg action into shoe/pad movement. Cool brakes don't care so much about a little air, but overheated brakes on a down hill where the drums have expanded and the coefficient of friction is diminishing, you would not want any air taking up pedal travel. Please endeavor to be thorough not just for day-to-day where the brakes work fine at 7/10ths, but for those potential moments where you need 10/10ths.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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