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

[mrgizmo04]

Yeah, you're not wrong...

Turns out this "budget" kit isn't all that budget at all if you track your car. Love getting sucked into the sunk cost fallacy, so determined to get it somewhat tolerable!

Yeah this budget kit is way over budget

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[mrgizmo04]

It's no longer “free” though. Yeah we all buy plenty of BMW parts but there's a limit. Store credit is a lot less useful to me these days since both of my M cars are in very solid mechanical shape. Half the time I want some small cheap part I struggle to even get to the $50 free shipping threshold without buying things I don't need.

I haven't done the math but the GTs with their larger 345mm rear rotors might move brake forces at the tire slightly rear which would decrease braking distance up to a point. I'm not sure the usual bias calc of torque applied to the rotors accounts for the extra lever arm.

If you bought original parts before the policy went into effect and keep using the parts, like rotors/pads/whatever, you can return and ask them to sweep the credit to your credit card or PayPal. That assumes that you (not you, but royal you), actually drive the car and use up the parts to make it worthwhile. I know some people replace rotors and pads once in 100k miles, that program prob won't be best for that use case.

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[mrgizmo04]

DCT60s... which admittedly aren't very good pads.

Never found a pad I like as much as the old PF01s, but the Hawks aren't even close.

I run split mu 70 front 60 rear and while I didn't love them initially, I grew to like them overtime and modulate the off/on switch nature of them.

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[Nate047]

Side note but related to 996 brakes, has anyone had success getting a properly firm pedal feel, with engagement up a little higher from the floor? Assuming everything is bled and in correct working condition.

[mrgizmo04]

Side note but related to 996 brakes, has anyone had success getting a properly firm pedal feel, with engagement up a little higher from the floor? Assuming everything is bled and in correct working condition.

Higher from the floor than what? Stock? My pedal is pretty firm, engages by barely presing the pedal, I think that's what converted a few locals to the kit . You have to bleed them quite a bit and doing it with caliper radially off the bracket so you can move the caliper around to get all bubbles out is key. I also dotched the rubber nipples, they seemed to get in the way of properly tightening the bleed screws as they dug into the threads.

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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.

[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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[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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[Nate047]

Copy that. I’ll bleed them again!

[Pklauser]

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

What happens running pads below 50% thickness?

[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.

[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?

[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.

[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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[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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