4S Brake upgrade or not..

Mike in CA

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The 90% figure that is tossed around as the percentage of braking handled by regeneration is a bit misleading, IMHO. First, it's a generalization based on average use, not necessarily on someone who drives their car in a spirted fashion, and I don't just mean on track. I like to drive my car briskly on the back roads around here and I guarantee that I'm not allowing regen to do 90% of the braking. Even in "normal" driving I use the friction brakes much more than 10% of the time.

Second, unless the Taycan is different than every other car I'm familiar with, more swept brake area results in shorter stopping distances, assuming similar tires and road conditions. Even if regen does a lot of the work slowing the car on some occasions, there will be times when you want the car to stop...NOW...and all else being equal, bigger brakes will produce shorter stopping distances.

FWIW, when Car and Driver tested a 2014 GT3 with PCCB's and Michelin Sport Cups (the car I owned before the Taycan) it stopped from 70mph in 139 feet. When they tested a 2020 Taycan 4S with PCCB's on Pirelli PZ4s it stopped from 70 in 147 feet. That Taycan gave away almost 3K pounds to the GT3 yet it stopped from 70 within 8 feet of it's little brother. Those are the brakes I wanted on my 4S.
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daveo4EV

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Under heavy use (the track) ceramics won’t fade
the taycan can‘t run long enough in track conditions to experience thermal fade even for the steel brakes - so pccb’s are really un-necessary for this vehicle.
 
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daveo4EV

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The 90% figure that is tossed around as the percentage of braking handled by regeneration is a bit misleading, IMHO. First, it's a generalization based on average use, not necessarily on someone who drives their car in a spirted fashion, and I don't just mean on track. I like to drive my car briskly on the back roads around here and I guarantee that I'm not allowing regen to do 90% of the braking.

Second, unless the Taycan is different than every other car I'm familiar with, more swept brake area results in shorter stopping distances, assuming similar tires and road conditions. Even if regen does a lot of the work slowing the car on some occasions, there will be times when you want the car to stop...NOW...and all else being equal, bigger brakes will produce shorter stopping distances.

FWIW, when Car and Driver tested a 2014 GT3 with PCCB's and Michelin Sport Cups (the car I owned before the Taycan) it stopped from 70mph in 139 feet. When they tested a 2020 Taycan 4S with PCCB's on Pirelli PZ4s it stopped from 70 in 147 feet. That Taycan gave away almost 3K pounds to the GT3 yet it stopped from 70 within 8 feet of it's little brother. Those are the brakes I wanted on my 4S.
we just had this raging debate (again on the Cayenne forum)
  • Tires stop the car - NOT the brakes
  • Tire grip is the limiting factor on stopping distance -not the brakes
  • ABS normalizes all stopping because it keeps the tires/brakes at tire grip threshold limits
  • all Porsche brakes can apply more force than the grip of the tires
  • C&D did a test of identicial porsches (911’s) with identical tires and found stopping distances of the two 911’s to be with in 1 ft of each other - steel vs. PCCB
  • the limiting factor on stopping distance is the maximum deceleration g’s force your tires can generate.
  • no manufacturer makes any stopping distance claims regarding ceramics vs. steel brakes
you can’t stop the car in less distance than the tires will allow - and all porsche brakes can maximize the tire’s deceleration grip.

https://rennlist.com/forums/cayenne-9y0-2019/1266809-build-advice-sought-2022-cayenne-gts.html
https://rennlist.com/forums/cayenne-9y0-2019/1266353-pccb-vs-steel-performance-difference.html

https://www.caranddriver.com/features/a15143696/the-power-to-stop/

Not surprisingly, the Corvette and the two Porsche 911s performed very well in this test. We grew weary trying to the get their brakes to fade. All three cars survived more than 35 back-to-back stops from 100 mph without a decrease in performance. That feat is even more amazing when one considers the relatively brief 20-second interval between stops.

The 911 with the PCCB system performed about the same as the other 911 and the Vette. The average stopping distances of the two 911s were within a foot of each other (305 feet), not surprising since both cars were wearing the same tires. The Corvette averaged 326 feet. The conclusion: PCCB buyers enjoy a 37-pound weight savings but not necessarily more robust brakes.
https://www.roadandtrack.com/car-culture/a10316984/why-braking-is-all-about-tires/

When ABS is activated, this tells the onboard systems that your wheel has stopped rotating, meaning that you’ve exceeded the maximum stopping force of the tire. In other words, your stopping distance is limited by the tire.
PCCB’s are good for the following:
  1. lighter
  2. no brake fade ever - not that fade is a problem with porsche steel brakes
  3. no brake dust
  4. better appearance
  5. longer life for street driving
PCCB”s are better brakes in every way -but not in any way you will ever encounter in street driving. For PCCB’s to be measurably better you’d have to be experiencing brake fade in normal driving circumstances - and with Porsche’s excellent brakes that is simply not the case. For street driving it’s very very very uncommon to have any circumstance where the brakes will be stressed or under termal fade - in those conditions the brakes stopping distance is dominated by road conditions and tire grip - the brakes are not the weak link there - the tires are so while PCCB’s are better - their characteristics will not come into play.

PCCB’s are a marketing triumph - they are in fact better, but not in any way you experience in normal street driving or even typical track scenarios for a street car - they are a the gold plated optical cable of the braking industry.
 
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daveo4EV

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https://www.roadandtrack.com/new-ca... time. The Taycan presents a unique challenge

A spokesperson told me that every Porsche is required to pass a braking torture test: 25 stops in a row, from 80 percent of a car's top speed down to 90 km/h (56 mph), with every fifth stop involving full ABS. For a car to pass, it has to generate between 0.8 and 0.9 g of deceleration every time.

The Taycan presents a unique challenge. Its 161-mph top speed is relatively low compared to other Porsche products. And the EV boasts ultra-quick acceleration, so it doesn't take long at all to reach 80 percent of top speed, around 129 mph. This meant that, during Porsche's braking test, the Taycan didn't have much time at all for the brakes to cool between stops.
_ALL_ of Porsche’s brake systems must pass the above test - not just the PCCB system - so unless you’re stopping from 80% of top speed 25 times in row I expect you will not find any real world performance difference between the various systems in terms of stopping/power/distance.
 

daveo4EV

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the Taycan can run about 15-20 min at “full pace” in track conditions - these are circumstances underwhich you could normally exceed the thermal limits of Porsche’s excellent steel brakes - however based on my 13 years of track experience 15-20 min is insufficient to overwhelm a good/excellent set of steel brakes even on track - i.e. you will not experience brake fade.

with the Taycan battery thermals are a weaker link than even tire grip or tire fatiuge - I’ve tracked GT3’s with steel brakes and with PCCB”s - it’s take’s a solid 25-40 min to get steel brakes into thermal fade, and PCCB‘s experience NO fade at these sorts of track session durations. The point is you can NOT run a Taycan fast enough and hard enough for long enough to overwhelm the brakes - you will overheat the battery at which point the car will limit power and/or you will run out of power - 15 min @ laguna seca uses 53% battery…

for 20 min or less of sprinting at full pace you will not exceed the thermal limits of Porsche’s excellent steel brakes, and after a solid 20 min of running hard the Taycan needs to come off track for a rest to cool the battery and recharge it.

PCCB’s are already a vanity purchase (I love them) but on my GT3 in a 45 min track session there is a real measurable advantage - NO FADE - but there is no measurable advantage for any legal street driving scenario.

if you want to stop shorter tires will do more for your stopping distance than any brake upgrade.
 
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Mike in CA

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_ALL_ of Porsche’s brake systems must pass the above test - not just the PCCB system - so unless you’re stopping from 80% of top speed 25 times in row I expect you will not find any real world performance difference between the various systems in terms of stopping/power/distance.
Well, just the other day I stopped from 80% of top speed 26 times in a row, so....:)

Fair enough, I'll bow to your analysis. I still love my PCCB's.
 

daveo4EV

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PCCB’s are dramatically better and provably superior brakes once you are into thermal fade for steel brakes - no question!!!

Under those circumstances thermally induced fade will dramatically elongate stopping distances because the brakes can no longer exceed the tire grip - so the limiting factor in stopping distance becomes the brake’s lack of ability to exceed the tire grip’s threshold - if you are routinely encountering thermal fade on your steel brakes then yes PCCB’s will perform dramatically better and reduce stopping distances…this is a proven fact.

so the question becomes:
under what circumstances are you routinely experiencing thermal brake fade with your porsche steel brakes?
HINT: one panic stop from 90 mph on the freeway isn’t enough - even 2 isn’t enough…

and once the brakes are cool again (doesn’t take long) you are back to having full braking effectiveness

so you have to be in a circumstance where you are braking hard enough and often enough to overhwhelm both the brake’s thermal absorption limits _AND_ not allowing the brakes to cool sufficiently between max power application…I find it hard to fathom a street driving situation in which both of those are true.
 

daveo4EV

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I’ve tracked sports cars for 13 years - I can only tell the diffrerence between steel and PCCB after about 30+ minutes on track - which even for track scenarios is uncommon - the problem is that at that point in time any DOT (Department of Transportation) rated tire is also experiencing grip threshold problems because they are getting greasy - so the combination of 30 minutes full pace tracking, street car weight, and tire longevity all conspire to increase braking distances … but in 20 min or less of full pace driving I’ve never experienced any serious thermal fade with Porsche’s excellent steel brakes…

with a good set of R-compound tires (not street legal) and a 1 hour track sessions - I did get Porsche’s brakes to overheat in about 35 min on track and braking was so compromised after 40 min that I came off track to let them cool - if I had PCCB’s I would expect to be able to run that entire session with no brake fade - yes PCCB’s are better brakes if you are in circumstances where you are routinely experiencing thermal fade with standard brake packages.
 

daveo4EV

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the fact that all these manufactures market ceramics as “better brakes” yet leave unspoken what aspect is actually better is marketing speak being done at the highest level.

ceramics _ARE_ better brakes - they are thermally superior, lighter, no brake dust, engineered for appearance, and will last much much longer than steel brakes in most any circumstances a street car will encounter.

all manufactures claim ceramics are better and they are - no manufacturer claims they improve stopping distances (other than brembo for their unqualified comparision to their F1 ceramics vs. “conventional steel brakes” what ever that means)

Porsche says: Better brakes​
Customer Hears: shorter stopping distances (because what else could better mean? in terms of brakes?)​
Porsche smiles: no comment - they are a $5,580 option (yellow calipers), $6,490 option (Black Calipers) - please make your choice before your build locks.​

the fact that you think better brakes means shorter stopping distance is reasonable expectations, but it’s not what you’re getting…

they know what they are doing…and Porsche is masterful in their marketing

PCCB’s are no question the best braking system on the market for all aspects of braking systems - what is left unsaid is that most braking systems today can stop your vehicle in as short a distance as possible one two or three times in a row because all braking systems are more powerful than your tire grip…but most braking systems will experience thermal fade far sooner than Porsche’s braking system - seriously drive a Corvette off the lot with stell brakes and onto the track and I defy you to not overheat the brakes by lap 3…not their ZR1 mind you - any other Corvette…BMW 3/4 series, same problem unless you get the competition model - Porsche - nope - their entire line off the lot can head to the track and you will most ikley not overheat the brakes - this is rare!!!
 
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daveo4EV

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the closest we have to Porsche admitting there is not stopping distance advantage for PCCB’s is this:

https://www.autoblog.com/2019/03/24/...r-race-tracks/

During the 2020 992-series Porsche 911 launch in Australia, Wheels magazine spoke to Paul Watson, Porsche Australia's in-country technical representative. When the conversation turned to carbon ceramic brakes, Watson surprised his questioners with the statement that "if you're doing club days we'd always recommend iron discs." This is an unexpected take considering how carbon ceramic rotors have been promoted as an open-secret weapon for track days.

Watson explained that "ceramic discs can degrade if you're hard on the brakes" and that "heat build-up will degrade the carbon fibers in the disc." Rotor wear comes no matter the rotor material, though.

The context of Watson's statement comes when he says, "When we first launched the discs we told people they'd last virtually for the life of the car and people were doing a number of trackdays and coming back to us saying 'I've worn them out.'" The issue isn't about the pure performance value of carbon brakes, but the cost-vs-performance value compared to iron rotors.

So when Wheels asked Watson who carbon ceramic brakes are for, he replied, "People who don't like cleaning their wheels. They don't leave a build-up of brake dust, so that's an advantage."
 

daveo4EV

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Porsches has extensive data on brake performance from their testing and development. They have overwhelming data - vast quantities of data - they know to the milimeter braking performance advantages and disadvantages under controlled conditions we can never imagine…

so do all the other manufacturers that offer ceramic brakes.

in nearly a decade of availability NO ONE - not a single vendor has ever claimed a stopping distance advantage as part of their marketing of these brakes…and you would think they would cause they would have the data to back it up and they makes minor claims all the time to sell various options no matter how minute the advantages…

and stopping distance is a BIG DEAL - being able to say PCCB’s will stop you 17 ft shorter (a full car length) from 70 mph would be a huge deal - even 5 ft…but complete and utter silence on this subject - not a single quote, hint, rumor, suggestion or innuendo across the entire industry that ceramic brakes stop you better in normal use…and this is from a company that claims a .000002 advantage of drag co-efficient improvements between the models of Taycan’s that have the power-charge cover port vs. the manual charge cover port…

this silence on this topic speaks volumes in my opinion - cause they have the data - they must have the data - and they _KNOW_ the answer - and yet they claim no advantage. Zero, nadda, zilch…
 

daveo4EV

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a vehicle with 265 kW of regenerative stopping power (not even touching the friction brakes) and street driving -and a battery system that contains both insufficient power and thermal capacity to run long enough to truly stress any braking system - PCCB’s are the ultimate success of Porsche marketing.
 

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Porsches has extensive data on brake performance from their testing and development. They have overwhelming data - vast quantities of data - they know to the milimeter braking performance advantages and disadvantages under controlled conditions we can never imagine…

so do all the other manufacturers that offer ceramic brakes.

in nearly a decade of availability NO ONE - not a single vendor has ever claimed a stopping distance advantage as part of their marketing of these brakes…and you would think they would cause they would have the data to back it up and they makes minor claims all the time to sell various options no matter how minute the advantages…

and stopping distance is a BIG DEAL - being able to say PCCB’s will stop you 17 ft shorter (a full car length) from 70 mph would be a huge deal - even 5 ft…but complete and utter silence on this subject - not a single quote, hint, rumor, suggestion or innuendo across the entire industry that ceramic brakes stop you better in normal use…and this is from a company that claims a .000002 advantage of drag co-efficient improvements between the models of Taycan’s that have the power-charge cover port vs. the manual charge cover port…

this silence on this topic speaks volumes in my opinion - cause they have the data - they must have the data - and they _KNOW_ the answer - and yet they claim no advantage. Zero, nadda, zilch…
of course they know. Folks have done this on YouTube. Results are exactly what you expect. Same stopping distance until steel heat fades.
 

charliemathilde

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For a not-EV, the Porsche ceramics have a nicer feel and stronger initial bite than the steel. Like “less dust” it doesn’t effect performance and is a matter of personal preference. Some folks don’t like a quick bite near the top.

Of course, this is pretty irrelevant to the blended EV braking.
 

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