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Posted by: Rusty May 25 2009, 09:25 PM

We had a discussion about this today... didn't really come to any agreement.

Thoughts?

Posted by: davep May 25 2009, 09:28 PM

No point to setting venting clearance (0.004") until everything else is completed.

Posted by: r_towle May 25 2009, 09:55 PM

It should not matter.
The piston is physically held there by the adjustment.
Fluid or not, it will still sit in the same place based upon the screw.

Rich

Posted by: john rogers May 25 2009, 09:56 PM

Rule of thumb is to set the clearance after you do the bleeding and then set it to 1/2 of the factory spec or your pedal will have a bit long travel.

Posted by: SGB May 25 2009, 10:01 PM

but you will have increased sensitivity to rotor warping- which
i think will always happen eventually.

Edit- of course, I do...

Posted by: drive-ability May 25 2009, 10:27 PM

Gentlemen ,

What are you talking about ? Rear venting ?

Posted by: SLITS May 26 2009, 07:47 AM

How close your a$$ is to the seat when you roll a cheek to phart!

Posted by: 914Sixer May 26 2009, 07:55 AM

Please disconnect the handbrake cables when adjusting the rear calipers. Added tension from these can sometimes mess things up.

Posted by: SGB May 26 2009, 08:40 AM

There is an adjuster on the rear brake calipers to set the gap between the pad and the rotor...

Posted by: drive-ability May 26 2009, 09:06 AM

That must be an aspect of the 914 factory brakes. My Carrera brakes aren't equipped with an adjustment . The was in the word venting.

I did some reading on the subject and I'm glad I did, it seems my rear calipers are installed (by Me) incorrectly on two points. I didn't shim them and they are upside down.

Posted by: Rusty May 26 2009, 09:14 AM

What spec do you use for that, Slits?

Posted by: Cap'n Krusty May 26 2009, 11:03 AM

It doesn't matter when you adjust them. What counts is the rotor is held flat against the hub and that the adjustment is made to .004". I do the outer, then the inner, then I recheck them both. The E-brake cables should be exerting NO force on the lever, other than taking up the slack in the lever itself. I've yet to see significant warpage in a rear rotor, but there's always a little runout. That's why you turn the rotor at least 360 degrees while checking the gap. It's marginally easier to bleed the brakes after the venting clearance has been set.

The Cap'n

Posted by: SLITS May 26 2009, 01:45 PM

My exact measurement is 0.125" ..... relieves the pressure on the cushion

I realize you may consider this setting loose, but it is absolutely necessary to get the appropriate audio from the flapping.

Posted by: MDG May 26 2009, 03:13 PM

I have squareweave in my '76 and basketweave in my '73 - does 0.125" work for both?

Posted by: SLITS May 26 2009, 03:44 PM

Basketweave diffuses the sound

Posted by: r_towle May 26 2009, 04:23 PM

Actually the basketweave enhances the sound while diffusing the smell.

Rich

Posted by: mskala May 27 2009, 06:35 AM

Semi-serious question, I've always figured if I set the clearance too low it will work
itself out, by wearing the pads a little, and if I set it too high, itr will work itself
out as the mechanism adjusts.

So aren't we really setting the clearance only for about the few days/weeks/months
until this happens?

Posted by: SGB May 27 2009, 07:50 AM

i don't think so...
I believe the clearance will track with the pad wear.

Posted by: Vacca Rabite May 27 2009, 08:15 AM

Nope. At least, that is not my understanding as to how it works.

The 914 rears do not self adjust at all, so you need to re-adjust them every 6 months or at the start of every driving season. As the pads wear, the calipers have to push them farther to get to the rotor, until they just don't work at all.

Zach

Posted by: mskala May 27 2009, 10:58 AM

If they are not meant to adjust, please explain the purpose of all the parts
inside other than the screw and locknut and why they are not directly connected
to the piston.

Posted by: Vacca Rabite May 27 2009, 11:26 AM

Read this, and find out.

http://www.914world.com/bbs2/index.php?showtopic=90625

The above thread should be in Classics, BTW.

Zach

Posted by: mskala May 27 2009, 12:13 PM

Okay, first of all, right in that thread, The Cap'n specifically states he's never
had to re-set the venting clearance between pad changes.

Second of all, if they were not designed to be self-adjusting, is there a spot in
the Owner's Manual that says to adjust rear venting clearance as part of
periodic maintenance and not just when putting in new pads?

Not that I'm saying they all work, or the design works well, but I believe that
every time the brakes are applied there is small force that is supposed to
make the mechanism move outward by rotating on the screw. But it's been
many years since I've had the parts out.

Posted by: Cap'n Krusty May 27 2009, 05:03 PM

That's NOT true. They self adjust as the pads wear. You DO NOT have to periodically readjust them.

The Cap'n