[s-cars] Sticky Big Red

[Tom Green]

Abe,

The 993tt big reds have a spring clip on top that holds the pad in  
place.  It hinges at one end and the other snaps in place.  Just  
squeeze the spring in to release the end.  If you use wear sensors,  
they may be clipped to the spring.  If you have the pad silencers that  
stick to the pad backing, they protrude into the piston, so you will  
have to push the pistons out to have room to remove the pads out of  
the piston recesses.  If you are careful you won't disturb the  
adhesive and they can be reused.  I like to loosen the bleed valve and  
put a bleed container on to catch fluid as I push the pad out to  
retract the pistons.  The pistons will move easier and you don't force  
the dirty fluid back up the lines and/or overfill the master cylinder  
reservoir.   If there are no pad silencers installed, the pads should  
come right out the opening.  If they have been there 5 years you may  
have to use lock pliers to grab the ears and pull.  You want to use  
the pad or a replacement block and a c-clamp if you need to push the  
pistons out so you can retract them straight and even.

The monobloc 996tt calipers are similar but use a pin with very small  
clips on the end to retain the pads.  Whichever system you have, just  
take your time and don't force a cocked piston.  They should retract  
smoothly but slowly.  If you use the bleed just open it when you are  
pushing the pad outward and only enough to allow the fluid to slowly  
flow and this will minimize bleeding required when you replace the  
pads.  The Motive pressure bleeders are great for the fluid flush and  
bleeding.

I don't know how much pad material you have remaining or what rotor  
you are using, but the pad should sweep its total area on the rotor.   
The 323 mm A8 rotor is not centered in the caliper using the RS2  
brackets unless the bracket is shaved, but the 2 mm shouldn't be a  
factor until pads are well worn.  I have assumed, since you mentioned  
no problems, that the caliper attaching bolts and the adapter were  
still torqued so that the caliper was properly aligned on the rotor  
and did not move.  You did not mention any difficulty removing the  
caliper, so there must not be much lip on the rotor edge.

There are lots of photos of the different brake upgrades on the web  
that should allow you to compare and determine what components you  
have installed.  If the brakes have been on your vehicle 5 years, it's  
probably information you need.


Tom '95 S6
          '95.5 S6 avant
Knoxville, TN


On Jun 7, 2010, at 10:58 PM, Abe Berman wrote:

> Removed caliper this evening.  On the inside of LF rotor the pad  
> seems to be only contacting the outer edge of the rotor surface, the  
> inner surface is rough with some light rust.  The pads seem to be  
> jammed into the caliper though and I couldn't easily figure out how  
> to remove them.  I did not do the conversion, so I am unfamiliar  
> with this caliper design and the online descriptions indicate that  
> the pads should be easily removed.  Is there a trick that I am  
> missing?
>
> On Mon, Jun 7, 2010 at 8:01 PM, Tom Green <trgreen at comcast.net> wrote:
> Abe, I mean clean the brake dust and crud off the caliper so you can  
> see the condition of the dust boots.  You probably are going to have  
> to remove the pads but not the caliper.  If one is torn it is  
> probably best to bite the bullet then and have them rebuilt.  Your  
> inspection of the lines, etc is time well spent.
>
> That sounds like a shop you use regularly that checked the balance.   
> Knowing the problem, I am sure they would also look for a leaky  
> piston or other possible causes.  The shop I use will tolerate my  
> inspection while they have the wheels off.
>
> I use Mintex red box and Hawk HPS for street pads.
>
> Tom '95 S6
>          '95.5 S6 avant
> Knoxville, TN
>
> On Jun 7, 2010, at 3:27 PM, Abe Berman wrote:
>
>> Tom,
>>
>> Thanks for the tips.  I did not closely inspect them, no, my  
>> mechanic actually did the balancing as I do not have access to a  
>> balancer.
>>
>> What constitutes an "exterior cleanup"?  I usually wipe down the  
>> caliper exteriors and the surrounding with a rag and simple green  
>> when I change winter and summer wheels.  I clean the rotors with  
>> brake cleaner should any simple green get on them.  I do not  
>> however remove the caliper or rotor.  I do inspect the lines and  
>> suspension components whilst down there.
>>
>> Any recommendations on pads and fluid from the group?  As far as  
>> performance needs, this is a spirited daily driver only, no track  
>> use.
>>
>> Thanks,
>>
>> a
>>
>>
>> On Mon, Jun 7, 2010 at 2:31 PM, Tom Green <trgreen at comcast.net>  
>> wrote:
>>
>>
>>
>> Did you have a chance to inspect the brakes while the wheels were  
>> being checked for
>> balance?  You don't mention any intervening maintenance since the  
>> brakes were
>> installed 5 yrs/30K miles ago.  It's certainly time for a fluid  
>> flush, exterior cleanup and
>> inspection, and perhaps a pad change.  If they are one piece  
>> rotors, turning them to
>> provide a new and true bedding surface for new pads is a good  
>> idea.  If the pads are
>> worn 1/2 or more, the reposition of the piston may be all that is  
>> needed along with the
>> new fluid, but if the pistons are out that far you might be advised  
>> to check behind the
>> dust boot to make sure the pistons are clean and add a little  
>> plasti-lube to insure they
>> retract smoothly when resetting for new pads.
>>
>> Then clean and inspect the brakes at least yearly and flush the  
>> fluid at least every two
>> years.
>>
>> Tom '95 S6
>>          '95.5 S6 avant
>> Knoxville, TN
>>
>>> -----Original Message-----
>>> Date: Mon, 7 Jun 2010 10:16:42 -0700
>>> From: Martin Kozaczek <mkozaczek at gmail.com>
>>> Subject: Re: [s-cars] Sticky Big Red
>>> To: Abe Berman <yellowcuda at gmail.com>
>>> Cc: s-car list <s-car-list at audifans.com>
>>> Message-ID:
>>> <AANLkTilHqJpT3apSTxEfyJ0goZq8B9FwRMlw0kiQ_1Dp at mail.gmail.com>
>>> Content-Type: text/plain; charset=ISO-8859-1
>>>
>>> I've read that some have had luck with taking the caliper off  
>>> (easier to
>>> work this way) removing the seal or boot whatever it's called,  
>>> then cleaning
>>> out the piston bore with liberal amounts o WD40 or equivalent,  
>>> clearing out
>>> with compressed air and reassembling.
>>>
>>> My calipers were new so I didn't bother, just sent them back.
>>>
>>> On Mon, Jun 7, 2010 at 10:01 AM, Abe Berman <yellowcuda at gmail.com>  
>>> wrote:
>>>
>>>> Thanks for sharing Martin.
>>>>
>>>> Hmm, guess I should check the archives.  I am hoping (read:  
>>>> praying) that I
>>>> don't need to replace the caliper(s).
>>>>
>>>> On Mon, Jun 7, 2010 at 12:40 PM, Martin Kozaczek <mkozaczek at gmail.com 
>>>> >wrote:
>>>>
>>>>> This seems to be a common problem with the older style two piece
>>>>> 928GTS/993 big reds or blacks.  I had a brand new set that did  
>>>>> it right from
>>>>> day 1.
>>>>>
>>>>> I tried everything and could not get it to go away, so I  
>>>>> returned them and
>>>>> temporarily replaced them with 996 C4 calipers while I wait for  
>>>>> my 996TT big
>>>>> reds.  Problem went away immediately when I put the 996 calipers  
>>>>> on.
>>>>>
>>>>>  On Mon, Jun 7, 2010 at 9:27 AM, Abe Berman  
>>>>> <yellowcuda at gmail.com>wrote:
>>>>>
>>>>>> Patient - 95.5 Avant mit Porsche "Big Red" front calipers
>>>>>>
>>>>>> Has anyone had problems with sticky Porsche calipers?
>>>>>>
>>>>>> I have been experiencing incidences of shuddering on the  
>>>>>> highway and feel
>>>>>> it
>>>>>> slightly (but intermittently) around town at lower speeds.   
>>>>>> Checked
>>>>>> balance
>>>>>> on all 4 wheels and its fine.  Tires are new and have no external
>>>>>> defects.
>>>>>>
>>>>>> I experienced this to a HEAVY degree whilst on the highway on  
>>>>>> Friday and
>>>>>> immediately pulled off at an exit.  Front Left wheel had  
>>>>>> serious heat
>>>>>> radiating off of it and a strong brake smell, all others were  
>>>>>> normal.
>>>>>>
>>>>>> I did some reading and it seems like the correct procedure  
>>>>>> would be to
>>>>>> clean
>>>>>> and lubricate slide pins and flush brake fluid/bleed brakes to  
>>>>>> eliminate
>>>>>> possible gunk/moisture in lines.
>>>>>>
>>>>>> The Big Reds were installed approximately 5 years/30k miles ago.
>>>>>>
>>>>>> Thanks in advance for any thoughts.
>>>>>>
>>>>>> Abe
>>>>>> Burlington, VT
>>
>>
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