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

[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.

[mrgizmo04]

How do the yellow and blue compounds compare in the real world?

Good to know FCP are carrying these now. Related: They also carry red/blue/yellow and Hawk DTC-60 for the D1001 shape of the Megane RS and DB9 calipers.

I went with DTC-60 because it was all that was available at the time, but I am curious about the EBC offerings.

I stayed away from EBC after reading other platform reviews on yellow, they barely handle heat and crumble, very "light" track duty pad. Blues are supposed to be for more serious track work, but I have not tried them either.

I might try Pagid yellow29 pads at some point as keep hearing positive vibes on those.

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[Nate047]

For the rears you would be looking at non S Boxster fronts. They offer quite a few, Hawk dtc60, Ferodo ds2500 (you might be able to get away on rears, depending on skill level), Pagid RSL29, Pagid 14/44 (backorder), and looks like they just started with EBC - yellow/blue are the "track oriented", red are street and are super low dust/no noise but high initial bite (those who like Textars might give them a shot, but I melted them on BBK on s2k in canyons, I never ran Textars, so can't compare exactly, but red street performance was stellar though, ymmv depending on car use case).

https://www.fcpeuro.com/Porsche-parts/Boxster/Disc-Brake-Pad/?position=Front&year=2004&m=20&e=40&t=6&b=10&d=&v=

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How do the yellow and blue compounds compare in the real world?

Good to know FCP are carrying these now. Related: They also carry red/blue/yellow and Hawk DTC-60 for the D1001 shape of the Megane RS and DB9 calipers.

I went with DTC-60 because it was all that was available at the time, but I am curious about the EBC offerings.

[mrgizmo04]

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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[SpaceJockey]

Thanks man!

[mrgizmo04]

Which track pads are you running? It looks like they only offer DS2500 for the rears.

For the rears you would be looking at non S Boxster fronts. They offer quite a few, Hawk dtc60, Ferodo ds2500 (you might be able to get away on rears, depending on skill level), Pagid RSL29, Pagid 14/44 (backorder), and looks like they just started with EBC - yellow/blue are the "track oriented", red are street and are super low dust/no noise but high initial bite (those who like Textars might give them a shot, but I melted them on BBK on s2k in canyons, I never ran Textars, so can't compare exactly, but red street performance was stellar though, ymmv depending on car use case).

https://www.fcpeuro.com/Porsche-parts/Boxster/Disc-Brake-Pad/?position=Front&year=2004&m=20&e=40&t=6&b=10&d=&v=

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[SpaceJockey]

FCP sells 996 track pads and CSL/ZCP rotors. That eliminates... 1/4-1/3 the cost of tracking

In every other way, the Brembo kit is hugely better. Lighter, pads last longer, rotors last longer, better pedal feel, no dust boot issues.

... I'm not entirely sure I made the correct choice.

Which track pads are you running? It looks like they only offer DS2500 for the rears.

[mrgizmo04]

Dumb question here: If you are on OE (Textar) pads, would you actually need more pedal travel to get the same braking power? Asking because I am assuming a decrease in piston area means more pedal travel needed and therefore more modulation. Thanks!

You have the ratio backwards. For same master cylinder, smaller caliper pistons will result in less pedal travel, but would require more leg force. Don't skip leg day! If you want to skip leg day, you can get a higher mu pad. At the wheel, for same master cylinder and leg force what provides more braking torque are any of the 3 - larger diameter rotor, larger diameter pistons, higher friction pad.

For illustration, similar to getting a cyringe (master cylinder) to fill up a bath tub (large piston, it will take all the fluid in the syringe + then some), vs if we decrease the area of the piston and now need to fill up a thimble from same syringe (in this case the plunger will barely move). You are moving fluid from one reservoir to another, if destination is smaller than origin, you need fewer pump/less travel. This is reverse of a hydrolic jack where you need to raise a car by pumping the small piston 10 times.

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