Let’s talk brakes on a 4S....standard red or PSCB...

[daveo4EV]

Do the PCSB provide any additional stopping power or increase in rotor or caliper size?

tire grip stops the car - not the brakes - the limit of stopping distance and power _IS_ the amount of grip your tires generate (and then limited by ABS)…not the brakes -

at ABS limits all brakes are the same…this is why your car will take longer (time & distance) to stop on ICE than asphalt regardless of what brakes you’re using…if you want to stop in less time & distance on snow/ice you change the tires, not the brakes…same is true for non-snow/ice conditions…tires stop the car - brakes can all exceed maximum tire grip.

the difference between braking system is _NOT_ braking effectiveness (they can all invoke ABS which is tire grip threshold) - it’s braking thermal capacity and brake dust differences…stopping distance between systems is statistically insignificant until you are into brake fade conditions (which is damm near impossible to get the Taycan in a situation where you’ll have brake fade).

porsche also tests all of the braking systems to pass the same test (25 stops from 80% of top speed in row with no pause and no fade)…so all three choices pass Porsche’s “torture” test for brake design.

Taycan adds the variable of regen braking - handling 90% of Taycan’s stopping in it’s life time (according to Porsche)

so the variables are:

1. appearance
2. brake dust
3. bragging right

all 3 of Porsche’s braking systems will stop the Taycan in about the same distance in the same conditions…and with regen braking handling 90% of the load there is reduced brake dust…

you are unlikley/impossible to overwhelm _ANY_ of Porsche’s braking systems with street tires and street driving, that leaves track conditions - where the Taycan does not have enough stamina to thermally overwhelm _ANY_ of the three choices before it runs out of battery (thermals or power)…

so we’re down to what do you want to tell people you have on the car - because that honestly at this point in the only difference…

it’s one of the great triumph of Automobile marketing that they sell different brake systems, and “better” brake systems, but leave unsaid what is better about the different brake systems. Most customers assume better brakes = better stopping distance - not true - better brakes = better thermal thresholds/limits and they are better _IF_ you can overwhelm the thermal limits of standard breaks yes PCCB’s are better - but you have to measure/ask yourself when am I going to overwhelm the steel brakes? the answers is in any normal legal street driving circumstance it’s impossible to thermally saturate Porsche’s excellent steel brakes…

• yes steel vs. PCSB vs. PCCB’s all offer “upgrades” in terms of braking
  • however not in a way that matters for any legal/normal street driving circumstance
• People assume better brakes = better stopping distance
  • not true
  • tire grip threshold (with ABS modulation) controls stopping distance not the brakes
• Porsche sells “better” braking systems but leaves “unsaid” in what aspect they are better
• they are in fact better
  • but not in any way that matters for vast majority of circumstances
  • the differences are in wear characteristics (Brake dust) and thermal capacity before you will experience “fade”
    • normal street driving it’s difficult/impossible to envision any circumstance in which you’ll “fade” porsche’s excellent base/steel brakes…
• the Taycan is also a special case
  • 90% of braking is regen
  • the Taycan lacks sufficient stamina in high performance circumstances to run long enough or hard enough to need high-thermal capacity brakes
  • you’ll run out of battery (power and/or thermals) before you’ll run out of braking capacity

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[MrBeanPT]

I'm settling on my build in a few weeks. Regarding the brakes, although what daveo4EV says makes sense, I'm almost sure that, at high speed, ABS will not trigger immediately, so I guess that better brakes make sense on those occasions. In particular in Europe where we drive faster on highways.

For me, better brakes would be for better looks only as I don't drive very fast frequently. However the 3k€ upgrade on the RWD is too steep for me, so I'll pass.

 

[f1eng]

1. appearance
2. brake dust
3. bragging right

Exactly.
On a Formula 1 car as long as the ducting is correct for the circuit there is zero difference in braking performance between cast iron and composite brakes.
Of course we all used composite once the wear problem was under control because of the weight.

I wouldn't consider them on a road car because the replacement cost is absurd for pretty well zero gain.

I have no experience of coated metal discs since I went directly from Iron to composite on the F1 car.
It may look nicer.

I am totally sure that from a braking pov the standard ones are effectively as good as it gets for driving on the road.

 

[daveo4EV]

I'm settling on my build in a few weeks. Regarding the brakes, although what daveo4EV says makes sense, I'm almost sure that, at high speed, ABS will not trigger immediately, so I guess that better brakes make sense on those occasions. In particular in Europe where we drive faster on highways.

For me, better brakes would be for better looks only as I don't drive very fast frequently. However the 3k€ upgrade on the RWD is too steep for me, so I'll pass.

ABS triggers when the wheels are “about to lock” - this can happen at any speed based on tire/road grip characteristics - when the wheels are about to lock ABS will “pulse” the brake pads to release the wheels to allow the wheel/tire to keep rotating allow driver control of the vehicle under heavy braking circumstances…

your car can stop no faster (short distance) than your tire grip will allow - all of porsche’s brakes can overwhelm tire grip - so the ABS threshold (tire grip) ‘normalizes’ stopping distances in that there will be no statistically significant differences in braking effectiveness between the 3 braking systems offered by Porsche (steel, PCSB, PCCB)

it has nothing to do with does ABS trigger “immediately” - it has to do with the fact that once it does trigger you are at the grip threshold of the tire and _ALL_ brakes can exceed tire grip threshold when they are cool (which they will be when traveling on the roads) - so high speed or not there is NO advantage in braking effectiveness between the 3 braking systems…it is a fact.

where PCCB’s _ARE_ in fact better is “thermal” capacity - i.e. in REPEATED high demand applications steel brakes can heat up and be thermally overwhelmed and then that will cause brake fade - under brake fade circumstances the brakes are no longer more effective that tire grip and braking distances will elongate…

so let’s review some facts:

• _ALL_ porsche brakes can stop a Porsche vehicle from 80% of top speed 25 times in a row with _NO_ brake fade (as required by Porsche’s own engineering standards)
  • porsche tests the cars/brakes to meet these standards
    • this includes the ”base” steel brakes on _EVERY_ Porsche sold
• I have tracked my GT3 with and without PCCB’s
  • at laguna seca race track (1:37 lap time, 11 turns) so you’re on the brakes every 9 seconds in one lap…
  • it takes over 15 laps before Porsche’s excellent steel brakes will start to demonstrate any brake fade…
    • that is 165 heavy brake applications in less than 30 minutes before Porsche’s steel brakes demonstrate any brake fade…
    • PCCB’s experience no fade even after 45 min on track
    • there is no difference in braking effectiveness (stopping distance) until the steel brakes demonstrate brake fade…
• the Taycan can only complete 8 laps @ Laguna at full pace before two things will happen:
  • battery thermals will cause the car to reduce max power
  • you will have used 55% battery
  • the Taycan will be no where _NEAR_ brake thermal limits in 8 laps or less
  • you will have to bring the vehicle off track to “rest” when this condition happens

You will _NOT_ overwhelm the steel brakes (regardless of how fast you drive) unless you plan to stop 25 times in a row with _NO PAUSE_ between stops from 80% of top speed @ full ABS stopping thresholds (foot to the floor full on panic stop 25 times in a row from 80% of top speed)

Taycan RWD 80% top speed = 116 mph
Taycan TurboS 80% top speed = 128 mph

so let’s review - you _MAY_ experience some brake fade with Porsche steel brakes _IF_ you launch control your Taycan TurboS to 128 mph - then brake at full pedal-to-the-floor-ABS full threshold braking down to 0 mph and then immediately repeat the launch control process _25 Twenty-Five_ times in a row!!! (no pause between trials to allow _ANY_ brake cooling)…

https://www.roadandtrack.com/new-cars/future-cars/a28915025/porsche-taycan-huge-brakes/#:~:text=A spokesperson told me that every Porsche is,every 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 … involving full ABS. For a car to pass, it has to generate between 0.8 and 0.9 g of deceleration every time.

now where are PCCB’s better? not in stopping distance, but rather “endurance or stamina” - so while Porsche’s steel brake can pass the test - they may only “just” pass the test - in 25 trials, where as PCCB’s may be able to do 40, 50 or 60 trials and still meet the 0.8/0.9 g’s deceleration criteria

so PCCB’s _ARE_ better - in that they can provide 0.8/0.9 g’s deceleration more than 25 times under these sorts of criteria - but lets review the FACT that Porsche’s steel brakes MUST pass the same test at least 25 times - Porsche says so…

I welcome any examples of any street driving circumstances where one feels they would use the brakes as documented from the test above and therefore be in a circumstance where they would exceed the thermal capacity of the steel brakes to repeat this sort of braking (with no pause or rest for braking cooling) 25 times in row…

regardless of a countries top speed limits - threshold braking 25 times in a row with full ABS with no pause for any brake cooling will lead to arrest or at least being pulled over for a conversation with local law enforcement…

tires stop your car - not your brakes
stopping distance is the same for all the brake systems
where PCCB’s are better is in thermal endurance (repeated applications in narrow time windows) - not in any actual scenario you will encounter unless you’re doing enduro racing with your Taycan -but again you don’t have enough battery to do that…

it’s about:

• appearance
• brake dust
• bragging rights

on the Taycan in particular there is _NO_ functional difference

tires stop the car not the brakes
and 90% of stopping is handled by Regen on the Taycan - so not even your brakes stop the car - LOL

 

[soawjo]

@daveo4EV thanks for your explanation of this, it’s not something I’d thought of before but now it seems obvious: the weak point in a car being slowed is not how much force the brakes can apply but how much grip the tyres have on the road

Now when I see Mat Watson on carwow or whoever doing a stopping distance brake test I’ll know he’s not really testing the brakes but how good the tyres are on that car

 

[daveo4EV]

@daveo4EV thanks for your explanation of this, it’s not something I’d thought of before but now it seems obvious: the weak point in a car being slowed is not how much force the brakes can apply but how much grip the tyres have on the road

Now when I see Mat Watson on carwow or whoever doing a stopping distance brake test I’ll know he’s not really testing the brakes but how good the tyres are on that car

correct - I’ve driven full spec race cars on slicks with tiny tiny brake rotors - the slicks when at temp stop the vehicle in amazing short distances from crazy fast speeds…

I’ve been amazed over the years at the difference _TIRES_ make - in all aspects - but in particular braking…

tracking my GT3’s street tires can generate 1 to 1.2 g’s in forward deceleration force…

swap in some racing slicks

my GT3 can generate 2.2 to 2.8 g’s in forward deceleration force - OMG - the stopping distance become next to nothing - and cornering loads are similarly higher - it transforms the abilities of the vehicle with the same brakes…

where braking systems different is not so much in stopping power (time & distance) - but rather in braking “endurance”…

brakes are fundamentally a thermal battery - they absorb heat (removing kinetic energy from the vehicle) - and then “cool” by dissipating that heat to the environment…if you ’fill up’ your thermal battery there is no place for the kinectic energy to go - so you get brake fade (no stopping power)

small brakes = small thermal battery = easy to get to brake fade
big brakes = big thermal battery = harder to get to brake fade

• your brakes don’t matter if they are all cool - cause you have maximum thermal capacity
• all brakes are the same when they are cool
• so most/all brakes can stop a car once from virtually any road speed
• and they can do it again if you let them cool (air cooling from normal driving)
• so you can stop most any car from 150 mph all the way down to zero once every 20 min - cause between each trial you will empty your thermal battery
• the trick with brake design is can you stop the car from 150 mph 5 times in less than 3 min
  • now that’s a torture test - since your brakes won’t fully cool - you need more thermal capacity to absorb more heat…cause there won’t be time between trials for you to empty the thermal battery (fully cool the brakes)

Porsche’s brakes are excellent - not in stopping distance - bur rather in thermal capacity - you can drive Porsche’s “off the lot” and onto the track and for the most part experience no brake fade - FEW _IF ANY_ street cars can do this…

My 2018 Model 3 Performance had _NO_ problems on track @ Laguna with brakes until about the 3rd lap - and then the brakes were horrible and into constant brake fade…the factory brakes are a joke (for track use) but fine for any street applications

my 2020 Taycan had no brake fade problems what so ever right up until I ran out of battery thermals and had to bring the Taycan in because I was down about 60% power because Porsche had reduced full power because the battery was at 132F - brakes = excellent - battery lacks endurance…

Porsche brakes are better because they have endurance characteristics most other manufactures do NOT provide - 90% of performance cars factory brakes won’t last more than 5 laps at full pace at Laguna for example - Porsche’s are fine - most every other car you need to upgrade the brakes if you plan to track the vehicle - not so with Porsche.

for street driving I’m at a loss to see any circumstance where 90% of most vehicle braking systems are insufficient - given you generaly cool the brakes through normal driving pace so endurance is not a factor

• it take over 25 minutes of full pace lapping to overwhelm a 911’s factory stock steel brakes…the same can not be said of other performance street cars or non-performance street cars
• it takes more than 25 minutes of full pace lapping to experience _ANY_ advantage from PCCB’s
  • but by then most street tires are no longer grippy - you’ve overheated them and they are greasy and lack stopping power because they will be overheated

PCCB’s offer vastly greatly thermal characteristics for high endurance braking applications
circumstances you simply can _NOT_ encounter in any legal street driving world wide
_IF_ you are to overwhelm Porsche’s excellent steel brakes - your tires won’t last long enough to outlast the brakes (street tires will get greasy and lack grip before your steel brakes will overheat)

to actually tap-into the advantages of PCCB’s you need to: run at full pace for a long time, have lots and lots of heavy braking, lack any recovery time between brake applications _AND_ have tires that don’t crap out and overheat - no street legal tires meets these criteria…

you need a race car, it needs to be on track, it needs to running at full pace, it needs to be more than a sprint race (25 min or more), and you need to be on slicks - then I’ll grant you PCCB’s are “better” - but again it won’t be in stopping distance or power - it will be in endurance (no brake fade).

 

[David Bennett]

it’s about:

• appearance
• brake dust
• bragging rights

on the Taycan in particular there is _NO_ functional difference

Over on another forum I use carbon brakes are lauded for their weight reduction and the improved front end feel due to less unsprung weight. Frank, raised it earlier and it might have been missed. Personally, I don't know if I could ever feel that on the road but to is stated as a reason to upgrade.

 

[gnop1950]

I have the PSCBs ordered on my Taycan 4S, along with the Mission E wheels. Appearance and lack of brake dust were more than sufficient for me to pay the extra for the upgraded brakes.

I'm pretty sure that I read somewhere that the first brake maintenance, other than checking brake fluid, is replacing the brake pads at 6 years due to age not necessarily wear, but can't find the reference. So, I'm not particularly concerned with the replacement costs.

 

[daveo4EV]

Over on another forum I use carbon brakes are lauded for their weight reduction and the improved front end feel due to less unsprung weight. Frank, raised it earlier and it might have been missed. Personally, I don't know if I could ever feel that on the road but to is stated as a reason to upgrade.

YES PCCB‘s are lighter - and in a way that really matters - less rotational mass - many claim they can feel the difference - I personally can’t…

• PCCB’s are vastly lighter than steel brakes
• PCCB’s offer superior to nearly infinite thermal capacity (endurance)
• PCCB’s have no brake dust
• PCCB’s ”look cool”

only the last two matter for street driving (appearance and brake dust)
you need better tires to really experience any endurance benefits (steel brakes thermal capacities will outlast most street tires for grip overtime on track) - when I’m tracking my street tires are losing grip long before my brakes are fading…
hard to see any advantage of weight on 2.5 ton vehicle

brake dust is reduced on a vehicle with regen because the brakes aren’t used 90% of the time - PCSB’s should approach PCCB’s levels of brake dust on a Taycan due to lack of any meanful usage - hell Porsche disables regen every day to “clean” the rotors on the Taycan - because otherwise the brakes would _NEVER_ be used in normal use…picture that engineering specification for the software…

Porsche Manager: Um, Frank we need you to code up some changes to braking system so that you use the friction brakes for a few miles every 24 hours or so…
Frank Brake Software Engineer: why, that will wear the pads and the rotors and regen wont’ be used
Porsche Manager: well testing has shown regen is so effective that we’re never cleaning the rotors due to lack of friction engagement, and we need to keep the rotors clean and ready so that when we do need them they will work…
Frank Brake Software Engineeer: OMG, you’re right - we use regen so much of the time - the friction brakes won’t work unless we keep the system engaged occasionally - ok I’ll get right on it.

 

[Genau]

Over on another forum I use carbon brakes are lauded for their weight reduction and the improved front end feel due to less unsprung weight. Frank, raised it earlier and it might have been missed.

A more effective way to reduce unsprung and rotational mass is to go with carbon fiber wheel cylinders. I was quoted $10k for this option on Forgeline wheels. An added benefit is much stiffer wheels during hard cornering.

 

[TayTaySD]

I have always wondered why racing cars don't add a small water reservoir to inject water through the interior of the rotors (from the bearing and use centrifugal force to blow the steam outward) when the rotors reach a certain temperature. When I track my car I wait for the rotors to cool down a little bit between outings then slowly pour water on the wheels rims (not brakes) which are thermally connected tho the brakes. Start each session with full capacity of the thermal mass at its minimum. Air is a notoriously poor conductor of heat(or cold).


Typical convective heat transfer coefficients for some common fluid flow applications:

• Free Convection - air, gases and dry vapors : 0.5 - 1000 (W/(m2K))
• Free Convection - water and liquids: 50 - 3000 (W/(m2K))

 

[Avantgarde]

ABS triggers when the wheels are “about to lock” - this can happen at any speed based on tire/road grip characteristics - when the wheels are about to lock ABS will “pulse” the brake pads to release the wheels to allow the wheel/tire to keep rotating allow driver control of the vehicle under heavy braking circumstances…

your car can stop no faster (short distance) than your tire grip will allow - all of porsche’s brakes can overwhelm tire grip - so the ABS threshold (tire grip) ‘normalizes’ stopping distances in that there will be no statistically significant differences in braking effectiveness between the 3 braking systems offered by Porsche (steel, PCSB, PCCB)

it has nothing to do with does ABS trigger “immediately” - it has to do with the fact that once it does trigger you are at the grip threshold of the tire and _ALL_ brakes can exceed tire grip threshold when they are cool (which they will be when traveling on the roads) - so high speed or not there is NO advantage in braking effectiveness between the 3 braking systems…it is a fact.

where PCCB’s _ARE_ in fact better is “thermal” capacity - i.e. in REPEATED high demand applications steel brakes can heat up and be thermally overwhelmed and then that will cause brake fade - under brake fade circumstances the brakes are no longer more effective that tire grip and braking distances will elongate…

so let’s review some facts:

• _ALL_ porsche brakes can stop a Porsche vehicle from 80% of top speed 25 times in a row with _NO_ brake fade (as required by Porsche’s own engineering standards)
  • porsche tests the cars/brakes to meet these standards
    • this includes the ”base” steel brakes on _EVERY_ Porsche sold
• I have tracked my GT3 with and without PCCB’s
  • at laguna seca race track (1:37 lap time, 11 turns) so you’re on the brakes every 9 seconds in one lap…
  • it takes over 15 laps before Porsche’s excellent steel brakes will start to demonstrate any brake fade…
    • that is 165 heavy brake applications in less than 30 minutes before Porsche’s steel brakes demonstrate any brake fade…
    • PCCB’s experience no fade even after 45 min on track
    • there is no difference in braking effectiveness (stopping distance) until the steel brakes demonstrate brake fade…
• the Taycan can only complete 8 laps @ Laguna at full pace before two things will happen:
  • battery thermals will cause the car to reduce max power
  • you will have used 55% battery
  • the Taycan will be no where _NEAR_ brake thermal limits in 8 laps or less
  • you will have to bring the vehicle off track to “rest” when this condition happens

You will _NOT_ overwhelm the steel brakes (regardless of how fast you drive) unless you plan to stop 25 times in a row with _NO PAUSE_ between stops from 80% of top speed @ full ABS stopping thresholds (foot to the floor full on panic stop 25 times in a row from 80% of top speed)

Taycan RWD 80% top speed = 116 mph
Taycan TurboS 80% top speed = 128 mph

so let’s review - you _MAY_ experience some brake fade with Porsche steel brakes _IF_ you launch control your Taycan TurboS to 128 mph - then brake at full pedal-to-the-floor-ABS full threshold braking down to 0 mph and then immediately repeat the launch control process _25 Twenty-Five_ times in a row!!! (no pause between trials to allow _ANY_ brake cooling)…

https://www.roadandtrack.com/new-cars/future-cars/a28915025/porsche-taycan-huge-brakes/#:~:text=A spokesperson told me that every Porsche is,every time. The Taycan presents a unique challenge.



now where are PCCB’s better? not in stopping distance, but rather “endurance or stamina” - so while Porsche’s steel brake can pass the test - they may only “just” pass the test - in 25 trials, where as PCCB’s may be able to do 40, 50 or 60 trials and still meet the 0.8/0.9 g’s deceleration criteria

so PCCB’s _ARE_ better - in that they can provide 0.8/0.9 g’s deceleration more than 25 times under these sorts of criteria - but lets review the FACT that Porsche’s steel brakes MUST pass the same test at least 25 times - Porsche says so…

I welcome any examples of any street driving circumstances where one feels they would use the brakes as documented from the test above and therefore be in a circumstance where they would exceed the thermal capacity of the steel brakes to repeat this sort of braking (with no pause or rest for braking cooling) 25 times in row…

regardless of a countries top speed limits - threshold braking 25 times in a row with full ABS with no pause for any brake cooling will lead to arrest or at least being pulled over for a conversation with local law enforcement…

tires stop your car - not your brakes
stopping distance is the same for all the brake systems
where PCCB’s are better is in thermal endurance (repeated applications in narrow time windows) - not in any actual scenario you will encounter unless you’re doing enduro racing with your Taycan -but again you don’t have enough battery to do that…

it’s about:

• appearance
• brake dust
• bragging rights

on the Taycan in particular there is _NO_ functional difference

tires stop the car not the brakes
and 90% of stopping is handled by Regen on the Taycan - so not even your brakes stop the car - LOL

One scenario you are ignoring here is spirited driving in long steep and curvy mountain declines. Thats when you wish for better brakes in any car but you can easily overwhelm brakes in 2-ton car before overwhelming the battery. Also in lower powered versions (like rwd), battery thermal capacity less likely to become a bottle-neck (vs turbo or turbo s).

 

[daveo4EV]

Regen is very effective in this space - but yeah - that can be one case - again even Porsche's steel brakes are excellent and there are few if any passes that will test them.

https://www.slashgear.com/audi-e-tr...the pavement was slightly lower at 40-degrees.

These typically slow the e-tron aggressively, but at the cost of efficiency. As a useful side-effect when you're descending something like Pikes Peak, it also helps keep the brakes cooler. At the halfway point, the brake rotor temperature was at 48-degrees, while the pavement was slightly lower at 40-degrees. The Park Ranger was shocked by how cool the brakes were, compared to what you'd expect from a traditional car.

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