S4 Brakes needing attention

[Prawn]

Marvelous day yesterday at CC, however I was having major brake problems in the afternoon.
BTW yes Jeff I know I should have used HiSpec and I know I should not have drilled Discs [img]images/graemlins/bowdown.gif[/img]

Prior to the trackday I had done the following :
1) New pads (EBC Green) installed, 1000 miles running before CC
2) Discs thouroughly cleaned out , ie holes etc
3) Brake fluid completly flushed through and replaced and system fully bled.
4) Could anything else cause the rumble / vibration or will this indicate a warped disc ?

Brakes were fine in the morning, but in the afternoon I was seeing lots of fade and more worryingly a major rumble and vibration under heavy braking.
This felt like the rotor was warped but went away on the drive home and has still not come back.
When I got home yesterday I looked at the brakes and the pads certainly look pretty black, also I have brake fluid that has leaked from the top of the resovoir on the servo.

Questions and conclusions :

1) Why would the fluid lead from the resovoir (yes the cap was tight), could this indicate boiled Fluid ?
2) IMO EBC Greens are c**p, I think they are too soft so therefore fill the holes in the disc too easily which leads to cooling problems. Any suggestions on a better pad choice, maybe something a little harder.
3) OK Jeff I'll bite [img]images/graemlins/thumb.gif[/img], I think the drilled discs are a problem area and may well not be up to track use in a heavier car that uses the front brakes more aggressivley.
Do Hispec do a direct fit replacement for the Porsche Disc, who do I need to talk to re this ?
4) Fluid, if as I suspect I have boiled the fluid I may need to look at uprating this

Any suggestions, comments or observations will be well received and Jeff please feel free to do your HiSpec sales pitch. [img]images/graemlins/thumbs.gif[/img]

[jeffw]

Dum dee dum dee dum.......err.....you talking to me ??? [img]images/graemlins/wink.gif[/img]

I've never tried EBC greens but I think that EBC will tell you to use a different pad for track days. The Ferodo DS2500 are designed as a road pad and for Endurance Saloon racing and seems to hold up well.

I would have thought that boiling fluid (if that's what you had) would not have escaped from the master cylinder. You might find that you have a leaking master cylinder.

I'm actually just going up to Dartford to HiSpec so I'll ask what is required to fit HiSpec discs to a Porsche set-up.

[Prawn]

That was even quicker than I thought you would be [img]images/graemlins/biggrin3.gif[/img]
Excellent service from the Brake Guru [img]images/graemlins/thumbs.gif[/img]

I would think that they will have a disc with the same dimensions, ie only the disc would be needed, bells would stay the same.
I also assume you have to renew the bell/disc bolts at the same time.

Cheers Jeff, look forward to hearing what they have to say

[DuncS3]

Hi Prawn,

sorry, just to make it clear for me you have the Porsche setup (calipers and rotors)?

Cheers

[jeffw]

Wouldn't call myself the brake guru.....I just know a man who is [img]images/graemlins/roundeyes.gif[/img]

Talking to Geoff at HiSpec regarding the Porsche set-up he thinks it can be done but he'll need the dimensions of the existing disc (width etc) or an old disc to measure up.

Does that help ?

[Prawn]

Yes Dunc you are correct

[Prawn]

Cheers Jeff,
I will try and get the dimensions at the weekend.

[Prawn]

Interesting link re porshe brakes :



Porsche Brakes

[jeffw]

So reading that thread you'll be OK with yours unless the cracks join up and bits of your disc fly off..... [img]images/graemlins/jawdrop.gif[/img]

Grooved discs anyone ?

[Prawn]

Grooves sound pretty damn groovy to me [img]images/graemlins/spineyes.gif[/img].
Once I get the dimensions for the discs it may be worth seeing if there is anyone else here who wants to swap from
the drilled to the grooved, maybe a lower price in it for a few pairs ?

[jeffw]

That sounds like a group buy....

When I was looking at various brake set-ups at CC there did seem to be different bells used on the various Porsche set-ups....don't know if that will make a difference or not.

[Prawn]

In theory they should all be the same if they are all
993 tt discs.
Ie same OD, number of mounting holes and hole PCD

[Prawn]

Ok Jeff,
Finally managed to get the ruler out and measure the brakes.
322mm x 32mm disc, Airgap in disc 16mm
Used braking face 60mm
10 x 6mm mounting holes on 182mm PCD

I will also get in touch with AP Racing to see what they are able to offer. [img]images/graemlins/thumbs.gif[/img]

[Joshie]

Some interesting posts on the Pistonheads forum about the Porsche brakes. Here are a couple..........

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Common problem, I've had the holes join up and bits fly off!, I use solid discs for racing because of this problem (trouble is these warp, new set every 300 miles). Porsche discs are the best (unless you start talking AP Racing etc), so slow down (yeh, right!!) or don't brake
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...I wouldn't fancy changing warped solid disks every 300 miles though [img]images/graemlins/mad.gif[/img]




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You are driving one of the worlds fastest production cars, it weighs in laden at over 1.6 tonnes, has over 400bhp and has the best brakes that Porsche have ever made, known by them as their 2000bhp brakes. In my opinion new discs every 8000 miles is a small price to pay, even at £500 per set. I have the same brakes on my 993RSR and they are renewed every year, at 2000 miles per year.

Surface cracking of any Porsche cross drilled disc is perfectly normal, they are usually caused by rapid heat build up (track days a favourite), but are only recognised as a problem when the cracks go through the disc or join the holes together, at which point they must be replaced.

As for the ceramics, yes we can do a set, but Porsche want £4200+VAT each for the disc alone. Call me if you want to order them.
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...Interesting, eh Jeff? [img]images/graemlins/grin.gif[/img]

[jeffw]

Prawn

I'm actually on client site at the moment but I'll talk to Geoff at HiSpec to see what he can do asap...

Joshie

If I could afford a Porsche 996 Turbo new then changing discs every 8K wouldn't be a worry..... [img]images/graemlins/tongue.gif[/img]

However I'm not in that position (no lottery win, pools etc) so Grooved discs are the best answer for me (8K + 4 track days and still fine)......

[img]images/graemlins/thumbs.gif[/img]