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

[mrgizmo04]

Not to derail or take this thread off topic from 996 Brembos but I think its still relevant; speaking of piston 'upgrades' from aluminum got me looking for my Megane Brembos and found this SS piston kit from RacingBrakes. Seems the FK8 CTR Brembos use the same size pistons as the Megane Brembos. What sucks is that it's so hard to find info on the exact size of the Megane pistons, I know theyre 40/40mm diameter but the depth I'll just have to assume/hope they're 30mm like the CTR's.

https://racingbrake.com/bh-41p/

For $266 it's not baaad, like yeah it sucks having to spend more money on the budget BBK (and spend the time and labor to rebuild), but even with the full rebuild kit they also sell ($407 with high temp boots upgrade https://racingbrake.com/bh-41bsp/) the Freakyparts Megane Brembo kit + Girodisc 345mm rotors is still cheaper than a Brembo GT 355mm front kit but not by much maybe after the rebuild kit I'd have saved $1k, but still much cheaper than any of the AP Racing kits on Essex (besides the 325mm kit they sell).

Their small 8350 kit is apparently for autox and street driving and not heavy track. I wish it was a 332 instead of a 325 rotor, that could work out, however the rotor is x32 thick. Z is running it for now.

What about titanium alloy pistons - https://www.silverlakeprojects.com/p...ns-for-porsche

I'm going to be trying these. The slight problem is the energy has to go somewhere, so if you are impeding xfer from pad to piston (by swapping from alu to ti pistons), pad will keep more heat. Not ideal for me because I faded DTC70 pads. Everyone is solving for dustboots so impeding heat xfer to pistons "should" help with that and keep you from boiling your fluid, however I don't want to keep the heat in the pad either and I have to solve for that problem also . But getting bigger x (impedance, shim, pad, etc) is like getting a bucket to fill up with water vs a cup. Yes the bucket can hold more water, but at some point it will still get overfilled. So depending how long you run sessions for the gradient will get flatter and flatter as everything saturates in heat.

Pistons I already put into the calipers they are barely lighter for both 40 and 36mm (like a gram or so) and 0.01mm larger in diameter vs alu. I expected this with Ti alloys. They should expand less than alu, so went in a bit tighter into the bores.

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[mrgizmo04]

Do you mean the pad thickness of the stock pad size vs the D1001? Or the caliper's max space for the pads? If the latter id assume the stock calipers had a much wider gap for pads, since Ive been having dust boots issues since moving to the Megane Brembos.

I should've mentioned in my previous post that I'm running rear 996 Brembos, their stock dust boots have been holding up fine. I didnt even rebuild them, just installed the used calipers with the factory boots since they looked good and still no cracks or issues, though I havent looked at them since the last track day with the PFC08 pads. I was running lower friction compound GLOC pads rear and I think the fronts were basically doing all the braking work so maybe that's why they haven't been heat stressed and cracked yet (no boots touching either with the 737 pad shape).

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, cooling will help tremendously. Stock tunnels are not enough. My first kit that I made was with 2" hoses (one you probably added to your watchlist), that became a pain taking down the bellypan because I routed it through there. Stock shield has a hole cutout on the back of it right in front of the bearing where I attached the hose, so you can go with that as part 1, that helped. After that, I trimmed the shield in such a way that my ball joints are all protected, and it does remove a tonne of shield to help radiate the heat and help with convection.

Rears I monitor, but yes, they don't require much maintenance. My rear pads are maybe 1/4 worn, while I'm on my third front set. Rear Girodisc dust boots are doing fine.

My temp reading on the rear caliper (Alcon sticker strips) barely get the first 121 degree bar (I fully trimmed the shield in rear, and use aluminum tape around the rubber bushings), while my front ones in similar location get to the 400 mark. Makes sense given that the paint I put on the edge of the rotors reads over 1400, I did fade DTC 70 pads at Laguna in T2 so they get over 1200 degrees, conducting into backing plates and ti shims to pistons (forget the dustboots at this point), I've had my 600 degree fluid boil on different occasions (with fuller pad), so then the outsides of the calipers see 400 degrees. That's hot. I feel bad for those seals.

[heinzboehmer]

Has anyone tried the OEM Porsche dust boots? When I did the 996 conversion on my car I rebuilt the calipers, and while shopping for parts I found that the only thing Porsche sold separately was the boots.

https://www.fcpeuro.com/products/porsche-disc-brake-caliper-rebuild-kit-centric-genuine-porsche-kit-14337013

https://www.fcpeuro.com/products/por...e-kit-14337009

Yeah those were the first set I fried.

[D-O]

Nevermind.

[George Hill]

TBH, if I were building a track car, I would just buy a 355x35mm Brembo Pista kit. IMO it's the best consumer track day setup for the front of these cars, but you can't get free consumables and the kit costs money.

I know you know this but the Pista kit doesn't have dust seals which is ironic because that is the whole point of this thread.

With that said I'm putting a Pista kit on my car

[Obioban]

No, they're not. And you're being charitable.

Let me ask this... all the cost – both in terms of money and time – to get prepped for the track, to go to the track, and spend the day on the track. Why not spend money to put proper parts on your car and maximize the precious time on track? Instead of doing all of that and ending up with brakes that only last for the first 10 minutes out of a 20 minute session, and every time you push the pedal, you're thinking they're not so great...

Just throwing that out there. I don't even care if you buy GiroDisc or not. I've realized that the time and effort commitment to getting to the track and maximizing every minute out there dwarfs saving a couple hundred bucks in a ridiculously expensive hobby.

Ha. They make it through a session without fade. If they didn’t, I’d be off this whole concept.

I only get ~2 events out them, but that’s fine when free.

It’s really just the seals that are annoying, and so far I’ve dealt with that by… ignoring it and not having dust seals.

[r4dr]

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.

No, they're not. And you're being charitable.

Let me ask this... all the cost – both in terms of money and time – to get prepped for the track, to go to the track, and spend the day on the track. Why not spend money to put proper parts on your car and maximize the precious time on track? Instead of doing all of that and ending up with brakes that only last for the first 10 minutes out of a 20 minute session, and every time you push the pedal, you're thinking they're not so great...

Just throwing that out there. I don't even care if you buy GiroDisc or not. I've realized that the time and effort commitment to getting to the track and maximizing every minute out there dwarfs saving a couple hundred bucks in a ridiculously expensive hobby.

[Obioban]

Anything is possible. And you're correct, since these calipers are all radially mounted, it would simply be a matter of caliper spacers and correspondingly longer caliper bolts. But it would end up being a custom hat (we could probably use an off-the-shelf Porsche ring so replacements are easy), and the price would be more reasonable if 5-10 people wanted to jump on.

However, we're also in a thread talking about free rotors... how many people would want to pay $1200 or so for a pair of assemblies?



What pads are you currently using via the FCP program?.

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.

[r4dr]

Also, as far as I know, the widest rotor I know of that comes from the factory with those Megane calipers is a 30mm-thick disc. I have to measure the calipers, but my question would be whether the caliper has clearance for something like a 34mm disc plus full thickness pads. And a few mm of space for stuff like titanium pad shields and allowing for pad tolerance.

[r4dr]

r4dr Is it possible to make larger rotors, like 355 mm and have them work with 996 calipers? Y’all sell larger rotors with caliper spacers for a bunch of Porsches, so why couldn’t it be done for our cars? 🤔

Anything is possible. And you're correct, since these calipers are all radially mounted, it would simply be a matter of caliper spacers and correspondingly longer caliper bolts. But it would end up being a custom hat (we could probably use an off-the-shelf Porsche ring so replacements are easy), and the price would be more reasonable if 5-10 people wanted to jump on.

However, we're also in a thread talking about free rotors... how many people would want to pay $1200 or so for a pair of assemblies?

For most of the time I ran the Brembo GTs, I had no ducting beyond factory/stock.



There's also free pads 🤣



I mean, it's not a fallacy if we can get it to work. Pads/rotors are probably 1/4 to 1/3 the cost of tracking, so if they can be made free, reliably...

That said, not gonna lie-- I miss my Brembo GTs. They were lighter, they had better pedal feel, I swear braking was better (as in stopping distances, though I understand why that should not be), and they were idiot proof-- with no effort I'd just run them till the pads were done, then on to the next pads. In the almost 15 years they were on my car, I had only 100% positive experiences with them.

What pads are you currently using via the FCP program?

TBH, if I were building a track car, I would just buy a 355x35mm Brembo Pista kit. IMO it's the best consumer track day setup for the front of these cars, but you can't get free consumables and the kit costs money.

[repoman89]

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.

[Obioban]

I remember you saying this and I've always kept it in mind. What's interesting is that the mass of the 355x32 rings isn't *that* much greater than the GiroDisc rings. They both have 48 vanes, but perhaps it might help having a proper rear setup as well. You were running a full cooling system with ducts and hoses, correct? Are you still using that setup with the CSL rotors?

For most of the time I ran the Brembo GTs, I had no ducting beyond factory/stock.

I know I'm biased and I don't pretend not to be, but there are more factors at play here than free rotors.

There's also free pads 🤣

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!

I mean, it's not a fallacy if we can get it to work. Pads/rotors are probably 1/4 to 1/3 the cost of tracking, so if they can be made free, reliably...

That said, not gonna lie-- I miss my Brembo GTs. They were lighter, they had better pedal feel, I swear braking was better (as in stopping distances, though I understand why that should not be), and they were idiot proof-- with no effort I'd just run them till the pads were done, then on to the next pads. In the almost 15 years they were on my car, I had only 100% positive experiences with them.

[SQ13]

r4dr Is it possible to make larger rotors, like 355 mm and have them work with 996 calipers? Y’all sell larger rotors with caliper spacers for a bunch of Porsches, so why couldn’t it be done for our cars? 🤔

[heinzboehmer]

The lifetime replacement savings are at the cost of higher consumable wear, more labor swapping consumables, and shorter lifespan of wear items in the calipers. You might have more pad left which will get you through your upcoming 2-day event, versus putting new pads in and keeping the old set as "spares" that never leave that shelf again...

I know I'm biased and I don't pretend not to be, but there are more factors at play here than free rotors.

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!

[r4dr]

Totally agree that having the boots fail this quickly seems like more a symptom of too high caliper temps than anything else. However, even with the full cooling setup you mention (like mrgizmo04 has), the boots still fail after some events. I'm not really too concerned about the boots, as they're fairly easy to swap, but more concerned about the seals inside the caliper. If those are made of the same materials, then they're likely not doing too well. Would not be fun to find out that they've failed at the end of a straight.

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.

That being said, I would pay good money for dust boots made of a material that's more tolerant to the temp these calipers see, just to avoid the pain of swapping them every once in a while.

You and me both.

And to address your cooling suggestions:

- Rotors: I'm running the subpar CSL rotors not because I think they're better than the Girodiscs, but because FCP sells them and having the lifetime replacement from them lowers track day cost. I suspect most people here are in the same boat.

The lifetime replacement savings are at the cost of higher consumable wear, more labor swapping consumables, and shorter lifespan of wear items in the calipers. You might have more pad left which will get you through your upcoming 2-day event, versus putting new pads in and keeping the old set as "spares" that never leave that shelf again...

I know I'm biased and I don't pretend not to be, but there are more factors at play here than free rotors.

- Pads: I'm running PFC08 pads all around (+ Girodisc titanium shims), so this should not be an issue.

Agreed. Love PFC pads.