I'm setting up restored rear calipers and the passenger side outside piston will not move when I try to adjust the venting clearance.

What do I need to do?

Also, the inside venting clearance adjuster doesn't seem to want to move. Looks like I'm taking the caliper off to check it out.

Common when the calipers sit for any length of time w/o fluid.

1. Pull the pads.
2. Using a high speed air wrench, "zip" the adjuster with a few quick blasts in a "Counter Clockwise" direction.

The piston should jump out and begin adjusting. The assembly lube has probably dried a bit and you now have the rubber seal against the side of the piston. The inner adjuster mechanism is spinning and the piston is not moving. The high speed zip (velocity, inertia) of an air wrech will overcome the mass of that internal adjuster. Use very short bursts and watch the piston. Once it moves you should be good.

For the inside piston, pull the handbrake arm back a couple of times to free the piston in the bore. If that doesn't break it free do the same thing on the inner adjuster in a "Clockwise" direction.

I can get the venting clearance adjusted on one caliper.

On the other neither the inside or outside venting clearance adjusters seem to work.

Read post #2...

OK, I've got the outside venting clearance working with the air wrench.

The inside one is still not working after a few "spins". I actuated the e-brake as well before trying. The e-brake barely moved the piston.

For the inside... Try one short burst in the opposite direction. Keep moving the arm. Then try clockwise again.

FYI, the arm will barely move the piston because it is adjusted in all the way. As you adjust it out you will get more engagement and it will move the piston the full allotted motion.

When you say "high speed air wrench", you mean a standard air wrench? I have a smaller grinder/buffer wrench which is very high speed.

Still no luck on the inner adjuster.

Clockwise on the inside adjuster to push the piston out, right?

Any chance it will break free in a day or so now that it has fluid? What about tapping the caliper?

No and no.

Keep moving the arm and trying both directions. Clockwise mostly but ok to do a short burst counter clockwise. Also, pull the arm back and try clockwise then.

Keep working it it should catch and then be good.

Don't forget the cotter pin in the castelatted nut...

Good info, I have the same issue on the passenger side rear. I'll give it a try once my car gets some bodywork done.

Still no movement on the inside adjuster.

Eric, thanks for all your help.

This thing has kicked my butt for tonight. I'll try again tomorrow.

Tried again this morning with my standard air wrench.

When you say "high speed air wrench", you mean a standard air wrench? I have a smaller grinder/buffer wrench which is very high speed.

I had this issue with one of mine. I believe the gear that drove the inner pistion in/out (not the splined gear that can fall out of the caliper - the one it turns) was damaged (air wrench wouldn't work for me either).

Off to Eric at PMB who quickly took care of the issue. Once back from PMB, it took me about 2 minutes to set the inner rear clearance.

Scott, the gear teeth on your adjuster post were broken off. That's very rare, especially on a freshly rebuilt caliper because:

A ) everything is new internally so nothing to bind and snap teeth on and
B ) as we discussed with yours, the piston has to get in there via that adjuster and gear, so, like yours, it would be impossible to get the piston in with broken teeth.

Broken gear teeth usually happen when a caliper is extremely old and bound up (kinda like Slits). Or when something gets pounded in the hole (kinda like scotty b). That said, it happened once, it could happen again. It's just very, very, very rare (for the edefication of those playing along at home). The "my calipers won't adjust" is very common and is sorted 99.9% of the time with a quick spin of the air wrench (like his outer adjuster).

Today is video day at the ranch so I may shoot a segment on this so everyone can have a better understanding of what's going on.

That sounds great

You are certainly going to wear clothes this time. It lends nothing to the instructional video unless you are impressing the head coaches at a college.

Finally, the inside adjuster started catching.

I tried the e-brake lever many, many times. Used the air gun many, many times. Still no function.

Then I tried warming up the caliper. After letting it cool for about 1 hour, tried the e-brake many times, and this time the adjuster broke free with just hand turning the adjuster.

Eric, you are the man. You have helped me immensely on this project. I couldn't have done this without your help.

Went out and checked my calipers earlier this morning. I got a set from PMB 3 months ago and they've been sitting ever since. They're going on the car this weekend. Both rear inner and outer adjusters turn and operate perfectly. That Eric and co. does good work.

Bump for a similiar,yet different problem.
This thread came up on search first,so..
I went out this morning to hook up the ebrakes on my car. It is a factory six with the original calipers, spacers and ventilated discs.The brakes had the correct venting clearances already, so I hooked up the cables to the arms, actuated the ebrake handle up and down ,checked the calipers,and the left rear is clamped down tight,both inside and outside pads.
The facory book says readjustment(venting) may be necessary,so I tried to back off the outside pad(counterclockwise) with the adjusters and the pad still wont budge.
I unhooked the cable from the actuating arm and still nothing,still clamped tight.
Any help would be great,
Thanks,John

laflaur..............I am thinking that you should turn the outer adjuster clockwise to retract the outer piston, and then the inner adjuster counter-clockwise to retract the inner piston.

What Jerry said.



Here's a little bit that helps me remember:

Imagine screwing a wood screw into a block of wood but... the screw remains stationery. Turn it clockwise and the block of wood comes toward you.

Imagine that "outside" piston in the same relationship. Turn the adjuster "clockwise" and the piston will retract, coming in towards you and off the rotor.

Both adjusters have a right hand thread pattern for economies of scale. This way ATE could use the same pistons on both caliper 1/2's. The internal adjuster is "Smack Dab in the Middle" of the handbrake arm so they used a gear to drive that adjuster. Meaning; it will now turn in the opposite direction due to the gear.

Again, same right hand thread pattern, same pistons... gear driven so it must go in a counter-clockwise direction to pull that piston off the rotor.

IMPORTANT: Gents, our adjusters have a small 4mm hex to adjust them. These get stripped "often" because 1. Fluids haven't been changed regularly or 2. The lock nut was not loosened before attempting to adjust the caliper.

Here's some things to consider when attempting to adjust your calipers:

1. Change your brake fluid before attempting to adjust the calipers. New fluid has a cleansing property. Maybe even run a quart of el cheapo fluid through your system and then move on to the good stuff for a final bleed. Use small Vise-Grips on your bleeders if they haven't moved in a while, "then" use a 7mm open end.

2. Move your hand brake arm back and forth to free the inner piston in the bore before adjusting. The arm should actuate the piston in the bore by roughly 1/8". Back the lock nut off the outer adjuster a tad and tap the outer adjuster (tap not beat). Be carefull not to go too far and jam the nut against the clip that "should" be there. The objective here is to get old, stuck pistons to move before you start to adjust them. If you can do this with a two step flush process (el cheapo fluid first) the fist fluid should help wash away some of the deposits.

3. Once you have all your pistons free and operating off the adjusters the way they should you can adjust to .004" on the high side of the runout. The high side may be different for the inner and outer pads. Basically; have them bind and back off a hair (literally) until the rotor spins freely. Then install and adjust your cables so you have a tight handbrake.

Thanks for the replys,I moved the outside adjuster clockwise and counterclockwise,then lefit and came back and the piston had loosened up. I will do #2 of Erics post right now and then adjust the handbrakes. BTW,I think it is because I have driven the car very in frequently lately that the piston bound up.
Thanks again,
John

There you go! Drive more frequently!

Gonna!
That is why I am going through ,bleeding brakes, lubing cables ,adjusting shifters,wheel bearings,etc,etc.
Thanks again!

great write up eric. always fun when "lefty loosy, righty tighty" doesn't apply and you don't know it.

k