Jos4DCivic

okay i did a complete front and rear disc brake job on my friends '93 accord ex. now the emergency brake wont grab tight anymore, it grabs a lil but it will roll if its on a steep hill. what could of gone wrong? the car has ABS system but i know the rear was done correct for sure. new pads n rotors n the caliper piston was turn in correctly to fit the new pads in so right now im clueless.

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91 Hatch SI

jeffcoslacker

You'll have to work the e-brake repeatedly to get the pistons to ratchet back into their correct position...right now they are wound in too far to be effective...just keep pumping the handle, you'll feel 'em come up into adjustment...

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You made three mistakes. First, you took the job. Second, you came light. A four man crew for me? F**king insulting. But the worst mistake you made...

...empty gun rack.

mpumas

I thought the e-brake activates the drum shoes not the pads. Am I wrong?

Glen_T

On Honda four wheel disc systems, the emergency brake mechanically pushes the piston out on the rear calipers, thereby causing the rear pads to squeeze the rotors. There is a spring loaded assembly within the piston that ratchets with every application, so it is self-adjusting.

It may also take a little driving before the new pads and the new rotor surface "burnish" or mate together well. But it sounds like the self-adjuster is just not there yet as Jeff stated.

Hope this helps....Glen

jeffcoslacker

If you look close at them, the piston is a two piece deal, the outer sleeve and the middle piston...the center is the ratcheting part, the outer sleeve is like a carrier, and provides positioning for the center part, in other words, the whole thing acts together as the piston when activated hydraulically by the service brake, the center screws outward when the e-brake is applied. The center can still be retracted enough that it acts only weakly on the pads by the e-brake, while the sleeve applies the service brake just fine...

It helps them perform better in the future if you lube the threads before retracting them also...

__________________
You made three mistakes. First, you took the job. Second, you came light. A four man crew for me? F**king insulting. But the worst mistake you made...

...empty gun rack.

mpumas

So, if I understand you correctly, the adjustment of the rear piston is done by excercising the emergency brake handle unlike the front calier which is adjusted by extending the piston out by pressing the brake pedal. Clever and now understandable.

jeffcoslacker

Some newer ones use a combo type, where the surface that makes up the "hat" area of the rotor is machined as a drum on the inside surface, and there is actually a miniature drum brake set for the e-brake under the rotor, seperate from the disc brake. Pretty neat, I think, keeps their operations seperate from eack other.

But yeah, the ones you have to screw in are a weird compromise....you can't really operate a push piston mechanically, and get any force behind it. At the same time you can't have the piston apply hydraulically in a screwing motion, it just won't act fast enough and the way hydros work the force involved is wrong.

So they made the piston a two-piece, dual action part, the outer acts as the hydraulic plunger (piston) and the center is threaded into it, rotated mechanically by a ratchet system when the e-brake is applied. So the piston is in ideal proximity to the pad as soon as the brakes are pumped a few times after replacement, the service brake portion of the system works the same as a standard caliper, but the center threaded part may still be twisted too far in to act with any force. The only way to bring them out into their normal position is to work the e-brake until they ratchet out into position fully. I just hold the release button in and pump the lever like a madman until I feel the lever begin to firm up...

When you are twisting the pistons with the tool, you can also feel the whole outer piston sliding in as you apply pressure to keep the tool on the piston face. Sometimes after running them in, you still end up having to push the whole thing back with a clamp if they are crabby...but not too often.

I like to pull the dust boot back and get all the dirt and scale out with WD-40 before pushing them in, to keep from forcing that crap back into the bore and threads...also keeps the dust boot from trying to spin with the piston if it's stuck to it, which will rip the boot, and the caliper will seize once exposed to road salt and grit and water...

__________________
You made three mistakes. First, you took the job. Second, you came light. A four man crew for me? F**king insulting. But the worst mistake you made...

...empty gun rack.