Front disc brake engineering question

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Mar 28, 2017 | 08:24 PM

blairsie

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Front disc brake engineering question

This may be a really dumb question, but what keeps the front pads off the front rotors when the pedal is released? I just replaced those pads, along with new rotors and bearings in my 93 and I couldn't readily see any counter force to the hydraulics in the system. It's obvious on the the rear, what with all those damn springs, but not on the front. For reference my setup is the rail slider front disc.

Mar 28, 2017 | 09:19 PM

Nothing Special

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From: Roseville, MN

Nothing, same as every other disk brake setup. The disadvantage is that there is slightly more drag in disk brakes than there is in drums. The advantage is that the pads wipe the disks clean so you don't get the exciting feeling of no brakes for the first few yards when you apply drum brakes after driving through a puddle.

(disks have other advantages too, that aren't related to the fact that the pads stay against the rotors)

Mar 29, 2017 | 12:00 AM

arse_sidewards

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The O ring between the piston and the bore is shaped to cause the piston to rock back a tiny bit when pressure is let off. Some calipers (not the ones on our trucks) have anti-drag clips that hold the pads apart to further reduce friction.

Mar 29, 2017 | 04:44 AM

'89F2urd

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Not to mention, the pads are being forced away from the rotor by the heated gasses generated by braking.

Mar 29, 2017 | 06:14 AM

blairsie

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Cool, thanks

I appreciate the responses. I'm teaching myself about this as I go. This form has been really valuable.

Mar 29, 2017 | 09:19 PM

moose4x4

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From: springfield Missouri area

Quote:

Originally Posted by arse_sidewards

The Gold star goes to Arse_sidewards!!!

Correct the oring is actually square and it flexs when brakes are applied, then flexes back to pull piston in just a tad off of the rotors.

Apr 2, 2017 | 10:57 AM

LeoJr

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From: Denton, TX

So if one caliper was dragging notably harder than the other, is it a bad caliper? I've swapped it twice with the same results.

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Apr 2, 2017 | 06:45 PM

wtroger

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Don't kid yourself disc brakes drag some all the time. And yes if one is dragging more than the other it is either bad or the rubber hose has issues.

Apr 2, 2017 | 07:10 PM

#10

Fastback460

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Quote:

Originally Posted by LeoJr

So if one caliper was dragging notably harder than the other, is it a bad caliper? I've swapped it twice with the same results.

Have you changed the brake hose as well?

I had the same problem with mine where one side would pull much harder then the other (and sometimes take longer to release) and it turned out to be the hose was collapsing, which didn't let the fluid come back quick enough when letting off the brake