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Posted by: Phoenix 914-6GT Apr 25 2008, 11:27 AM

Okay, I know I could look it up. However, due to time constrants I am hoping someone knows off the top of their head what the venting clearance is supposed to be for the rear brakes. I need to reset mine as I just found that the ebrake was partially ingauged when I set it last.

Thanks

Jon

Posted by: dbgriffith75 Apr 25 2008, 11:29 AM

I can't confirm it off the top of my head, but I think it's supposed to be set at 32 thousandths, or .032 on your feeler gauge.

Posted by: Phoenix 914-6GT Apr 25 2008, 11:44 AM

well... I will give that a try unless someone can say otherwise.

Thanks

Posted by: sww914 Apr 25 2008, 11:45 AM

My feeble brain tells me .006". I think that .032 will give you a long pedal.

Posted by: effutuo101 Apr 25 2008, 11:47 AM

6mm between piston and disk (no pad) If you adjust with pads in, take out the retraining spring.

Posted by: sww914 Apr 25 2008, 11:48 AM

This Pelican article says .008".
http://www.pelicanparts.com/techarticles/914_brake_pads/914_brake_pads.htm

Posted by: rhodyguy Apr 25 2008, 11:49 AM

look down a few threads for the bump jon. venting clearance...

Posted by: dbgriffith75 Apr 25 2008, 11:49 AM

...then what the crap am I thinking of...?

Posted by: sww914 Apr 25 2008, 11:51 AM

Spark plugs?

Posted by: r_towle Apr 25 2008, 11:55 AM

.004

Posted by: Eric_Shea Apr 25 2008, 11:58 AM

Ding, ding, ding, ding, ding, ding, ding, ding, ding, ding, ding, ding, ding, ding, ding, ding, ding, ding, ding... we have a winner:

.004

Factory manual stated .008 and all of the Haynes/Clymers were drafted off that figure.

Then the factory sent out a TSB stating that .004 is correct. Adjust on the high side of your runout obviously.

Posted by: Phoenix 914-6GT Apr 25 2008, 12:36 PM

Thanks guys... I knew it wouldn't take long before Eric chimed in

Posted by: bulitt Sep 28 2017, 06:30 PM

QUOTE(Eric_Shea @ Apr 25 2008, 01:58 PM)

Posted by: plays with cars Sep 28 2017, 09:17 PM

QUOTE(bulitt @ Sep 28 2017, 05:30 PM)

Posted by: bulitt Sep 29 2017, 05:08 AM

Nothing like dragging up an old thread to remind myself how valuable Eric's tutorials have been over the years.

Posted by: r_towle Sep 29 2017, 07:23 AM

QUOTE(bulitt @ Sep 29 2017, 07:08 AM)

Nothing like dragging up an old thread to remind myself how valuable Eric's tutorials have been over the years.

Posted by: GeorgeRud Sep 29 2017, 09:22 PM

Now known as Spongy Pedals?

Posted by: DaveO90s4 May 13 2018, 07:07 AM

Resurrecting an old thread.

If the 'correct' venting clearance is 0.004"is there any downside to a lesser clearance, such as adjusting each adjuster so the the relevant pad simply just 'kisses' the rotor, then backing it off very very very marginally to give minute clearance? (with hand brake cable disconnected of course).

In other words, applying the spirit of the adjustment specification, if not the letter of the adjustment specification?

Why do I ask? Well using with feeler gauges in that area is pretty fiddly and I'm not sure if in practice it is necessary. I understand the reasons for not having too big a clearance. Just touching then a tad loosened would seem to my mind to do the job.

Yes? No?

Thanks

Dave O

Posted by: Krieger May 13 2018, 07:51 AM

Your wheel bearings have some play in them.

Posted by: Vacca Rabite May 13 2018, 09:24 AM

Dave,
.004 clearance is pretty minute. Literally, that's the same as the width of a piece of human hair. It would be hard to get that minute a measurement going off feel. Chances are you would have way too much clearance.

Zach

Posted by: The Cabinetmaker May 13 2018, 10:49 AM

engineers don't just pick a number out of the air. They do things for a reason. Would you guess, and adjust your valves at .002 instead of .008 just because you have trouble getting the feeler gauge in place?

Posted by: DaveO90s4 May 13 2018, 03:08 PM

Hi Zach - yes I agree. 0.004" is indeed minute. In practice it is "lightly touching less that minute amount" - hence my question. Thanks for your reply - I did use feeler gauges to set the venting clearance - was just wondering if feeler gauges were essential.

And in reply to The Cabinetmaker in a similar vein. I'm not bloody stupid you know. I own and maintain six aged Porsches, do all my own mechanical maintenance. Adjusting venting clearance with feeler gauges is not at all the same as adjusting tappets with feeler gauges. With tappets too much gap makes for a rattly engine and poor performance. Too little makes for burnt out valves. And allowance needs to be made for expansion as the engine components - alloy and steel alike - heat up.

With the brake venting Porsche clearly, at 0.004", wanted it to be as close as practicable without actually touching. As Zach helpfully notes, less than the thickness of a human hair.

As I say above, I have done the job properly as per spec. I was just interested to know if using feeler gauges was absolutely necessary for a competent experienced person who has done this task previously with the use of feeler gauges.