Porsche Brembo 996 BBK Conversion-- let's figure out how to fix the dust boots/seals

[Obioban]

Good point, how would one go about doing this?

INPA has a procedure that does this while you pressure bleed the brakes. You start it, it tells you what corner to open, and it activate the DSC valves for that corner.

PITA, but if you get air in the module it's the only way to get it out.

[BigRussia]

Just wanted to see the brake pad comparison vs stock overlaid, like attached. Front 996 kit pad is barely larger than stock (if you can call it that). D1001 pads I think are slightly larger.

Yes, I do have a pic! And of the rear 737 vs stock.


I finally got my APracing caliper temperature strips after USPS lost the Alcon ones I first ordered, and will be going to my usual home track this Sunday. I also sucked it up and bought the Vorshlag brake cooling deflectors. Im going to get the front brakes temperature readings without them during the first couple sessions, then go home during the very long break between 2nd and 3rd session and attempt to install the deflectors (along w fresh temp strips) then go back to the track. So should be an ideal test of the effectiveness (or lack of) of the deflectors!

I am not planning to cut or trim any of the dustshield, my thinking is the deflectors should direct their air right into the hole the dustshield have that’s right at the hub, and thus right into the center of the girodisc hats and hypothetically get sucked up from the center up the discs’ vanes (rather than shooting air onto the exposed inward rotor face with the dust shields cut)

[mrgizmo04]

Ah ok, so nothing specific to this kit.

Well...point of a bbk is not to stop better/faster/etc, it is to manage heat better and have more heat capacity, that's what first "b" in bbk is, big. 996 kit front pad is pretty much same size as stock, so it does not provide more heat capacity. Rotor hat is made to block air flow , kit itself came from a mid engine layout where not as much front stopping power was required. So everything on this kit is undersized for our car to extract max performance on track. So like I said, for daily highway cruising, enjoy the kit. For those going fast on track, we are dealing with a lot of pain as this kit gets overwhelmed , and for some of us that goes beyond just melted dust boots.

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[Pklauser]

Heat capacity of the already small pad exits stage left and you are left with a pad that gets really hot, wear accelerates exponentially, other issues ensue with potentially fading pad, boiling fluid, etc.

Ah ok, so nothing specific to this kit.

[D-O]

Copy that. I’ll bleed them again!

If you have not tried one, the Motive Power Bleeder is really nice.

[mrgizmo04]

Good point, how would one go about doing this?

Either keep driving and bleeding like you are getting into ABS, or use INPA/Schwaben, they have options to activate.

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[mrgizmo04]

What happens running pads below 50% thickness?

Heat capacity of the already small pad exits stage left and you are left with a pad that gets really hot, wear accelerates exponentially, other issues ensue with potentially fading pad, boiling fluid, etc.

This doesn't really apply for street use unless you are going to be hammering every corner from 10k feet to sea level. If you are running good clip on track, going into a day with 50% pad is not ideal, but as long as you have the right expectation and are prepared for what is to come, you'll be ok. Also this is very track dependent, there are some tracks you could get away with very worn pads, others absolutely not. Just another part of prep depending on track you will be going to and optimizing brake performance.

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[heinzboehmer]

Get the scoops installed into the stock opening in the shield in front of the wheel bearing and we can run again .

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PET-CF filament arrives in a couple days! Will be printing scoops and evacuation ducts when it does.

[Nate047]

I would guess you got air in the DSC module and will need to actuate that as you bleed them. Pedal firmness is not an issue with this setup.

Good point, how would one go about doing this?

[Obioban]

Interesting point about bleeding with the caliper not on the bracket. Because yea, what I mean is vs stock. Engagement on my recently installed retrofit is lower and softer. I have not begun to troubleshoot it yet and I know it’s been covered a million times. But any pro tips from the vets would be very much appreciated.

I would guess you got air in the DSC module and will need to actuate that as you bleed them. Pedal firmness is not an issue with this setup.

[Pklauser]

we already know we can't run pads below 50% without seeing issues, etc.

What happens running pads below 50% thickness?

[Nate047]

Copy that. I’ll bleed them again!

[mrgizmo04]

Interesting point about bleeding with the caliper not on the bracket. Because yea, what I mean is vs stock. Engagement on my recently installed retrofit is lower and softer. I have not begun to troubleshoot it yet and I know it's been covered a million times. But any pro tips from the vets would be very much appreciated.

I'd say still air somewhere in there. I had to bleed them multiple times when I initially got them, which was frustrating because I wouldn't see bubbles at end of each bleeding cycle, just to go on a drive and get a soft pedal, come home, bleed again and see bubbles again. Bleeder screw caps with those rubber rings to prevent caps from being lost can also be a problem getting into the threads.

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[mrgizmo04]

The seals are a few degrees of separation away from the pads / rotors and aren't in direct contact with the pads themselves. Heat in brakes is more localized than people realize -- even the rotor tabs (where the hat fixes) can be noticeably cooler than the swept surface itself, and they're only an inch or so away from each other.

I guess what I'm saying is that I hear your concern but I've never seen anything that would lead to caliper seals failing and causing catastrophic loss of brakes. Even when they get tired (and they do, which is why we rebuild calipers) the pistons will still apply pressure to the pad, but the rollback behavior might not be as clean as a fresh setup.

Assuming I trust the numbers from the paint and Alcon sticker strips, the outsides of rotor get to over 1400 degrees, DTC70 pads faded once so prob get over 1200 degrees, 600 degree fluid I boiled a few times and Alcon sticker on the outside/side of caliper showed arounf 400 degrees. So somewhere in there the pressure seals see at least several hundred degrees. I just pulled my old set of seals out, as I was emailing you, they look a lot flatter and feel less pliable than the new set, some of that is expected from new vs old, but I do wonder how many events those can last in the torture chamber that is the tiny 996 caliper ...

This is also running the "experiment" on 5 track days in cooler conditions from Oct to Feb. I'd hate to see what happens as conditions deteriorate - rotors get to half life or less, ambient starts climbing into 70/80 and up, we already know we can't run pads below 50% without seeing issues, etc.

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[Nate047]

Interesting point about bleeding with the caliper not on the bracket. Because yea, what I mean is vs stock. Engagement on my recently installed retrofit is lower and softer. I have not begun to troubleshoot it yet and I know it’s been covered a million times. But any pro tips from the vets would be very much appreciated.