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

[heinzboehmer]

Curious if the piston seals are affected by the high temp.

I was unable to find Brembo seals when I rebuilt my calipers, so I used the girodisc ones. Supposedly made for high temps and track use, but we'll see.

[Epsilon]

Curious if the piston seals are affected by the high temp.

[heinzboehmer]

Womp.

Looking forward to seeing how the high temp dust boots hold up on my friend’s car.

Really hoping they hold up, as I don’t want to be dealing with heat shields (or, worse, both combined aren’t enough).

Looking forward to that too. Do you know where those are from?

At least the boots are easy to swap without removing anything besides pads...

[Obioban]

Womp.

Looking forward to seeing how the high temp dust boots hold up on my friend’s car.

Really hoping they hold up, as I don’t want to be dealing with heat shields (or, worse, both combined aren’t enough).

[heinzboehmer]

Brembo dust boots did not survive a track day . Granted, this track day was extra long, so the brakes got a good workout. 7, 30 min sessions vs the regular 5, 20 min sessions.

Setup was 996 calipers, ZCP rotors, PFC08 pads, titanium shims and brake ducts (which are kinda useless with the new rotors). Even with the cooling/heat shielding, this still happened:



That was the only boot that fully failed, but I found a few others that were a bit melted. Replaced with a girodisc one for the time being. I'll likely replace all of them before the next track day just to see how those hold up.

[mrgizmo04]

That was day 2 of that pad being used...

... though admittedly in a caliper that got stuck.

One day too long . Past half point on the pads, this kit just doesn't have the capacity or evacuation efficiency. Once combined with rotor being less than half life, it gets more interesting yet, need to keep optimizing. FCP might drop our warranty sponsorship if we keep sending back half good pads/rotors.

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[mrgizmo04]

Just my gut feel says there is something to that. The thickness and mass of the new brake pads creates a thermal barrier for the caliper and boots. Do folks use titanium heat shields as well? Like these:

https://girodisc.com/titanium-shield...c2s-c4s-front/

Yes I run 1mm hardbrakes.com version, but girodisc makes their own version.

To reiterate, I run 1mm (believe thickest they make) Ti shims with Vorshlag cooling deflectors (which move more air than hoses) and still have issues with dust boots.

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[0-60motorsports]

You need to know what kit you have, what generation, what size (diameter as well as thickness rotor) 355 vs 380, x32 vs x35, they would have different piston diameters to ensure correct bias.

That page from Zeckhausen is only useful if you are replacing pistons and know exact diameters you need as well as what generation your caliper is. It only shows that they are split into different height/length of the piston, depending on the generation, however the diameters of the pistons are different.

For example, a 355x32 ST40 kit uses 42/38mm pistons, a 355x32 ST60 (pic below) version uses 36/36/30mm combination.

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Got it. I'll just have the guys remove the calipers and measure the boots and take pics, This way we'll have a reference. Also the kits are both Second gen if I had to guess.

[mrgizmo04]

Interesting so all the pistons fit the st60 are the same size? Thanks.

You need to know what kit you have, what generation, what size (diameter as well as thickness rotor) 355 vs 380, x32 vs x35, they would have different piston diameters to ensure correct bias.

That page from Zeckhausen is only useful if you are replacing pistons and know exact diameters you need as well as what generation your caliper is. It only shows that they are split into different height/length of the piston, depending on the generation, however the diameters of the pistons are different.

For example, a 355x32 ST40 kit uses 42/38mm pistons, a 355x32 ST60 (pic below) version uses 36/36/30mm combination.

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[Mayan-Viking]

I'll second the nod Pat McCleish. If anyone ever runs into technical issues beyond their scope, he's a great asset to call. He is a master at this brake stuff, he knows more about the specifics on these kits than anyone I've met. He's a real car guy too, so that helps. He once helped me out when I was in a real pinch and thought I had no options. He proved otherwise. Great guy to boot.

[0-60motorsports]

https://www.zeckhausen.com/catalog/i...4_213_239_8587

Interesting so all the pistons fit the st60 are the same size? Thanks.

[D-O]

Anyone know the E46 M3 Application Stoptech ST60 and ST40 piston sizes? Thanks.

Obioban Thanks for the link to Automotive Brake Solutions. I'm going to order some seals and pads from him once i get the above info.

https://www.zeckhausen.com/catalog/index.php?cPath=24_213_239_8587

[Obioban]

Another random thought I had as partial(full?) solution to baked dust boots and to not have them pop out when pads get low...is to run new pads every track day (or at least replace at 50%?). You need something to absorb the heat, as the pad wears, it can take less energy and conducts more of it to pistons (Ti shims can only do so much as a barrier, at some point they get oversaturated too). As pad wears, pistons protrude more out of the bores, and as the pistons heat up, they conduct the heat to the hot air around them/dust boot. And the dust boot on a protruded piston is a bit stretched/stressed so melts/cracks as it absorbs all that energy. Air is a poor conductor and is an insulator. So if the pistons were more retracted into the bores (what happens when pad is newer), heat exchange would happen between piston and bore/caliper as well as fluid in caliper, so dust boot would not absorb as much energy to melt. That's what engineering hunch is telling me.

Ian's first pic shows pads rather low and pistons protruding, was similar case when mine developed crack from heat.

This is obviously not wallet friendly or FCP warranty policy friendly, but I Iike to share my random wannabe engineer thoughts. 🤣

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That was day 2 of that pad being used...

... though admittedly in a caliper that got stuck.

[nyc951]

Another random thought I had as partial(full?) solution to baked dust boots and to not have them pop out when pads get low...is to run new pads every track day (or at least replace at 50%?). You need something to absorb the heat, as the pad wears, it can take less energy and conducts more of it to pistons (Ti shims can only do so much as a barrier, at some point they get oversaturated too). As pad wears, pistons protrude more out of the bores, and as the pistons heat up, they conduct the heat to the hot air around them/dust boot. And the dust boot on a protruded piston is a bit stretched/stressed so melts/cracks as it absorbs all that energy. Air is a poor conductor and is an insulator. So if the pistons were more retracted into the bores (what happens when pad is newer), heat exchange would happen between piston and bore/caliper as well as fluid in caliper, so dust boot would not absorb as much energy to melt. That's what engineering hunch is telling me.

Ian's first pic shows pads rather low and pistons protruding, was similar case when mine developed crack from heat.

This is obviously not wallet friendly or FCP warranty policy friendly, but I Iike to share my random wannabe engineer thoughts. 🤣

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Just my gut feel says there is something to that. The thickness and mass of the new brake pads creates a thermal barrier for the caliper and boots. Do folks use titanium heat shields as well? Like these:

https://girodisc.com/titanium-shields-porsche-996-turbo-c2s-c4s-front/

[0-60motorsports]

Anyone know the E46 M3 Application Stoptech ST60 and ST40 piston sizes? Thanks.

Obioban Thanks for the link to Automotive Brake Solutions. I'm going to order some seals and pads from him once i get the above info.