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> Can't Adjust Venting Clearance On Rear Caliper, WTF?
Spoke
post Nov 20 2012, 07:39 PM
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Jerry
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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.


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Eric_Shea
post Nov 20 2012, 07:52 PM
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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.
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Spoke
post Nov 20 2012, 08:01 PM
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I can get the venting clearance adjusted on one caliper.

On the other neither the inside or outside venting clearance adjusters seem to work.
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Eric_Shea
post Nov 20 2012, 08:03 PM
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Read post #2... (IMG:style_emoticons/default/biggrin.gif)
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Spoke
post Nov 20 2012, 08:09 PM
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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.
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Eric_Shea
post Nov 20 2012, 08:14 PM
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For the inside... Try one short burst in the opposite direction. Keep moving the arm. Then try clockwise again.
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Eric_Shea
post Nov 20 2012, 08:16 PM
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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.
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Spoke
post Nov 20 2012, 08:42 PM
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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?
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Spoke
post Nov 20 2012, 08:43 PM
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Any chance it will break free in a day or so now that it has fluid? What about tapping the caliper?
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Eric_Shea
post Nov 20 2012, 09:02 PM
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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.
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Eric_Shea
post Nov 20 2012, 09:11 PM
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Don't forget the cotter pin in the castelatted nut...
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JmuRiz
post Nov 20 2012, 09:14 PM
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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.
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Spoke
post Nov 20 2012, 09:22 PM
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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.
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Spoke
post Nov 21 2012, 06:57 AM
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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.
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sfrenck
post Nov 21 2012, 08:20 AM
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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.
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Eric_Shea
post Nov 21 2012, 08:34 AM
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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.
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JmuRiz
post Nov 21 2012, 09:11 AM
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QUOTE(Eric_Shea @ Nov 21 2012, 06:34 AM) *

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 (IMG:style_emoticons/default/smilie_pokal.gif)
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SLITS
post Nov 21 2012, 12:04 PM
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QUOTE(Eric_Shea @ Nov 21 2012, 06:34 AM) *

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.


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.
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Spoke
post Nov 21 2012, 12:46 PM
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(IMG:style_emoticons/default/piratenanner.gif)

Finally, the inside adjuster started catching. (IMG:style_emoticons/default/beerchug.gif)

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.

(IMG:style_emoticons/default/pray.gif) (IMG:style_emoticons/default/pray.gif) (IMG:style_emoticons/default/pray.gif) (IMG:style_emoticons/default/pray.gif)
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Gint
post Nov 22 2012, 01:59 PM
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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.
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