PCCB out braked the steels last night on 5th gear.

PCCB out braked the steels last night on 5th gear.

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Discussion

Schmed

1,300 posts

20 months

Monday 18th November
quotequote all
Surely it depends on whether you've ever experienced brake fade. Having had an occurrence of this on the road (not racing btw), it is terrifying. Am I to understand ceramics have a much greater tolerance to fade in which case it seems to be a simple case of just sign me up, (budget permitting...) ?

Koln-RS

2,890 posts

160 months

Monday 18th November
quotequote all
This argument comes up with regular frequency and in my view no one knows which is best - contributors will post what they believe supports their opinion - for or against.

The OP stuck his neck above the parapet by highlighting a positive claim about pccbs, so inevitably it will generate some contrary comment.

Same arguments apply to Manual v PDK, 2wd v 4wd, NA v Turbo, Bose v Burmeister, Black v White.......
Everyone makes their own choices, although, of course, cost can be a determining factor.

ChrisW.

3,279 posts

203 months

Monday 18th November
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In hard bucks my Surface Transform discs have now half paid for themselves in reduced brake pad consumption.

They do run cooler, they don't fade, there may or may not be handling advantages given the total masses in play .... I am very pleased with the choice I made but I have stepped outside the Porsche warranty parachute.

Yes it is possible to make steels work very very hard, but they are consumables and also are now expensive.

Digga

28,570 posts

231 months

Tuesday 19th November
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I've run a 997.1 GT3 on track on both PCCB and then, swapped out for Alcon (same sized discs) steel conversion. This is merely my take, but it is pretty good back-to-back, because it's on the exact same car.

I do a lot of mtb riding and on anything steep, rocky and rooty, having 'feel' for brakes (it's simply too steep not to brake, but impossible to brake all the time without losing the front or rear end) is utterly essential. Having successfully ridden trails steep enough that the back tyre buzzes your arse, in the French and Swiss Alps, Spanish Pyrenees and even on Snowdonian slate, I feel qualified in that regard.

CARBON
  • Definitely more initial 'bite'
  • Definitely less (virtually zero) variance in the initial bite
  • No variance in pedal effort/travel after repeated laps
  • A bit 'binary' and trickier to modulate force
STEEL
  • Much more progressive bite - proportionate to pedal effort
  • Some slight variance in initial bite
  • Some variance in pedal effort/travel corner to corner, lap to lap, but only minor
  • Exceptionally easy to modulate brake force. Makes trail braking very, very easy.
Although the steel discs are appreciably heavier - front steel is 10kg, compared to about 5kg - I really could not discern too much difference in steering or ride as a result. I might were I able to swap brakes in the pits and try it out, but IMHO the difference is probably not much.

With regard to repeated laps, as Hunter66 says, the tyres will be the limiting factor in either case, especially on hotter track temperatures IME. I am not a racing driver, or even a particularly good track day driver, but I have had a lot of practice at being average, and the above is my opinion.

LaurasOtherHalf

15,930 posts

144 months

Tuesday 19th November
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I’ve said it before, but a Porsche experience day at Silverstone (the 987 spyder day) trying steel back to back with carbon and back again left me in no doubt I’d go carbon every time.

Steering feel, ride quality and suspension compliance were dramatically better and that’s before the instructor insisted on proving the difference in performance in repeated application.

I get the worry about carbon fragility’s (especially if you’re not on top of pad wear-is it not a case of change as soon as the wear indicators come on?) but to say there’s no performance benefit is spurious.

In the 997RS (steel brakes) we’ll do 2 laps each and by the fourth lap of the ‘ring you do need to watch where the pedal will go-it’s never failed but you start to lose the retardation in the first inch or so of travel. Enough to put you off your line when braking deep.

Digga

28,570 posts

231 months

Tuesday 19th November
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LaurasOtherHalf said:
by the fourth lap of the ‘ring you do need to watch where the pedal will go-it’s never failed but you start to lose the retardation in the first inch or so of travel. Enough to put you off your line when braking deep.
You explain that 'variation' nicely, much more lucidly than I was able, but I completely get that description.

I know I'm not good enough to do those ten tenths braking a manoeuvres, but even so, there is the occasional stop - like Shell Oils at Oulton - where it is 'interesting'.

Porsche911R

Original Poster:

17,900 posts

213 months

Tuesday 19th November
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I am a steel fan boy if you have the money you can get a setup which is nice for £10k and it's nice to pick a pad for your type of driving.
a 10k set up will also match the pccb weight !!! as Porsche still use cheap heavy calipers !!

oem Porsche vs oem Porsche the PCCB will win every time imo, even it's it due to the size alone, that's just physics moving the caliper out will give more force as you cannot lock a wheel at 80mph plus so PCCBS will always out brake a steel car at speed.

add in the weight #(now much bigger over a 997) you also have to stop A LOT less weight which again physics alone means less weight is easier to stop.

then you have the sus advantages on bumpy road it might be able to keep the tyre on the road better.

I did notice the 5th gear test road was a bumpy as hell bit of tarmac.

this is the ONLY test were we have seen like for like cars on the same day above legal speeds in porkers where PCCB choice gives a much bigger disk.

the Jag test I am sure the ceramics are the same size disks. the C&D test was different cars, different days plus a GTS weighing more.

it's not the same as PDK vs manual, we all know PDK changes gear faster.

any way I posted the results as it was interesting as we have ALL BEEN asking the questions for years. it's the same 4 or 5 die hards who poo poo PCCB's ! it's always a given on a 987 platform that PCCB are night and day, it's never been night and day for the GT3 market.


Porsche911R

Original Poster:

17,900 posts

213 months

Tuesday 19th November
quotequote all
Yellow491 said:
Answer a question R,if the weight saving is that critical to performance of a road car on road tyres,why are the dampers and spring rating not any different of steel over ceramic on the gt cars,and for that matter mag wheels.
PASM has big windows to allow 2 people and luggage etc etc.

the 1st thing Manthey do to make a car faster is rip PASM out.

we own road cars, but if you are serious about track days then even 10kg out is a plus, taking 100 kg out is night and day.

you hill climb , what's 100kg worth time wise up a small UK hill climb ?

I wanted to hill climb my Spyder, I was told my PCCB car did not qualify in the oem class !!! and it would have to go in modiflied !! which was daft vs what a fully modded race car looks like and weighs !! this was back in 2010 I wonder if the regs have changed now PCCB are more common.

Edited by Porsche911R on Tuesday 19th November 10:27

isaldiri

5,033 posts

116 months

Tuesday 19th November
quotequote all
Porsche911R said:
add in the weight #(now much bigger over a 997) you also have to stop A LOT less weight which again physics alone means less weight is easier to stop.
Wrong - physics states weight is not relevant in braking distance.

Porsche911R said:
this is the ONLY test were we have seen like for like cars on the same day above legal speeds in porkers where PCCB choice gives a much bigger disk.

the Jag test I am sure the ceramics are the same size disks. the C&D test was different cars, different days plus a GTS weighing more.
Wrong again, not exactly a surprise there.... The F type has bigger ceramic rotors and the C&D test was on the same day with the same car, a 997S. I merely mentioned the SportAuto one as another data point. What did I say before about reading posts properly as well?


Porsche911R said:
any way I posted the results as it was interesting as we have ALL BEEN asking the questions for years. it's the same 4 or 5 die hards who poo poo PCCB's ! it's always a given on a 987 platform that PCCB are night and day, it's never been night and day for the GT3 market.
And yet you choose to ignore 2 different results just so you can shout about this one test.

I'll repeat myself from an earlier post

It is simply a question of what one wants to ask.

Perhaps here on the 718 T or the 987 as you say the ceramic brake option will brake better as it has more capability in the braking system. What I do dispute is that ceramics are always going to brake better than steels as you are incessantly claiming. On a GT car that is not and will not be the case.

isaldiri

5,033 posts

116 months

Tuesday 19th November
quotequote all
Digga said:
LaurasOtherHalf said:
by the fourth lap of the ‘ring you do need to watch where the pedal will go-it’s never failed but you start to lose the retardation in the first inch or so of travel. Enough to put you off your line when braking deep.
You explain that 'variation' nicely, much more lucidly than I was able, but I completely get that description.

I know I'm not good enough to do those ten tenths braking a manoeuvres, but even so, there is the occasional stop - like Shell Oils at Oulton - where it is 'interesting'.
Do you still have that variance on I assume pagids with your alcons? That variation seems to me at least more of a pad/fluid issue than anything necessarily specific to brake material. Although ceramics have if I'm not wrong a different master cylinder as the braking system requires more force to work properly (which is why ceramics have greater initial bite and for me anyway more difficulty in modulation) so perhaps that also helps to mask any slight initial softness in the brake pedal when the brake lines and such start getting very hot.

Digga

28,570 posts

231 months

Tuesday 19th November
quotequote all
isaldiri said:
Digga said:
LaurasOtherHalf said:
by the fourth lap of the ‘ring you do need to watch where the pedal will go-it’s never failed but you start to lose the retardation in the first inch or so of travel. Enough to put you off your line when braking deep.
You explain that 'variation' nicely, much more lucidly than I was able, but I completely get that description.

I know I'm not good enough to do those ten tenths braking a manoeuvres, but even so, there is the occasional stop - like Shell Oils at Oulton - where it is 'interesting'.
Do you still have that variance on I assume pagids with your alcons? That variation seems to me at least more of a pad/fluid issue than anything necessarily specific to brake material. Although ceramics have if I'm not wrong a different master cylinder as the braking system requires more force to work properly (which is why ceramics have greater initial bite and for me anyway more difficulty in modulation) so perhaps that also helps to mask any slight initial softness in the brake pedal when the brake lines and such start getting very hot.
Yes on Pagid and Alcon, with decent fluid.

The car is PCCB standard, so will be running whatever master cylinder it came with.

The variance is very slight, although the initial 'bite', the power of PCCB is quite pronounced by comparison.

isaldiri

5,033 posts

116 months

Tuesday 19th November
quotequote all
Digga said:
Yes on Pagid and Alcon, with decent fluid.

The car is PCCB standard, so will be running whatever master cylinder it came with.

The variance is very slight, although the initial 'bite', the power of PCCB is quite pronounced by comparison.
Ah ok interesting and yeah I did forget your car was an original ceramic one. Difference has to be pad/rotor interaction for the initial bite then and nothing to do with the master cylinder as I was thinking paperbag

Yellow491

1,435 posts

67 months

Tuesday 19th November
quotequote all
Porsche911R said:
Yellow491 said:
Answer a question R,if the weight saving is that critical to performance of a road car on road tyres,why are the dampers and spring rating not any different of steel over ceramic on the gt cars,and for that matter mag wheels.
PASM has big windows to allow 2 people and luggage etc etc.( still does not get away from correct dampers and springs fir given weights,especially unsprung.

the 1st thing Manthey do to make a car faster is rip PASM out. yes and put good non standard dampers and springs,having been there for a three day course last month.

we own road cars, but if you are serious about track days then even 10kg out is a plus, taking 100 kg out is night and day. 10kg makes no change,100kg may be a bit ,but down to grip and driver with same bhp.

you hill climb , what's 100kg worth time wise up a small UK hill climb ? Not a lot in a tin top,open wheel proper race car some differance,but not as big as you might expect.On a fast circuit when i used to do a lot more racing,100kg came more into play,especially in the wet.When my car lost a lot of weight we revalved the dampers and springs.

I wanted to hill climb my Spyder, I was told my PCCB car did not qualify in the oem class !!! and it would have to go in modiflied !! which was daft vs what a fully modded race car looks like and weighs !! this was back in 2010 I wonder if the regs have changed now PCCB are more common. Thats nonsense,if standard fitment,you can use and always been the same,what scrutt said that! Road production is road production.

Edited by Porsche911R on Tuesday 19th November 10:27

arcamalpha

781 posts

112 months

Tuesday 19th November
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isaldiri said:
Wrong - physics states weight is not relevant in braking distance.
Really? (Genuine question). Kinetic energy is proportional to mass. Brakes convert kinetic energy into heat.

Acceleration (and deceleration) is proportional to mass too...

996Targa

42 posts

94 months

Tuesday 19th November
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I may be wrong here but as the wheels, discs etc are not part of the sprung weight of the car any increase or reduction in their weight should not affect spring rates on otherwise the same vehicle which would explain why they don't change from one disc material to another (or wheel).

isaldiri

5,033 posts

116 months

Tuesday 19th November
quotequote all
arcamalpha said:
Really? (Genuine question). Kinetic energy is proportional to mass. Brakes convert kinetic energy into heat.

Acceleration (and deceleration) is proportional to mass too...
If your brakes can cope with that heat dump converted from the kinetic energy, yes braking distance is not affected by mass.

Mass cancels out ln both sides of the energy equation, ke (0.5mv^2) and work done (force x distance) where force = ma where acceleration (deceleration) is dependent on the coefficient of friction from tyre to road.

So mass affects whether the braking system can cope with that amount of heat but not in terms of braking performance.

Edited by isaldiri on Tuesday 19th November 19:22

Taffy66

3,091 posts

50 months

Tuesday 19th November
quotequote all
arcamalpha said:
isaldiri said:
Wrong - physics states weight is not relevant in braking distance.
Really? (Genuine question). Kinetic energy is proportional to mass. Brakes convert kinetic energy into heat.

Acceleration (and deceleration) is proportional to mass too...
Agreed,,Try stopping a 2T SUV travelling at the same speed as a 1.5T saloon with both wearing the saloon's brakes..Quite simply braking's purpose is to overcome a vehicle's momentum and slow it down or stop..When the mathematical formula for momentum is mv or mass(kg) multiplied by velocity(Meters/second) then its pretty obvious that a vehicle's mass has as much effect on braking performance as the speed its travelling.
I knew all of this when i was 10 years old so its rather perplexing that some adults have still not grasped the most elementary of high school physics.

isaldiri

5,033 posts

116 months

Tuesday 19th November
quotequote all
Taffy66 said:
I knew all of this when i was 10 years old so its rather perplexing that some adults have still not grasped the most elementary of high school physics.
laugh

Indeed, could not agree more really!

arcamalpha

781 posts

112 months

Tuesday 19th November
quotequote all
isaldiri said:
arcamalpha said:
Really? (Genuine question). Kinetic energy is proportional to mass. Brakes convert kinetic energy into heat.

Acceleration (and deceleration) is proportional to mass too...
If your brakes can cope with that heat dump converted from the kinetic energy, yes braking distance is not affected by mass.

Mass cancels out ln both sides of the energy equation, ke (0.5mv^2) and work done (force x distance) where force = ma where acceleration (deceleration) is dependent on the coefficient of friction from tyre to road.

So mass affects whether the braking system can cope with that amount of heat but not in terms of braking performance.

Edited by isaldiri on Tuesday 19th November 19:22
Good point! So I guess the reason heavier cars/trucks typically take longer to stop in reality is the ability of the braking system to absorb heat. How much can be absorbed, how quickly etc. Also the deceleration isn't constant for the duration of the stopping distance etc etc.

isaldiri

5,033 posts

116 months

Tuesday 19th November
quotequote all
arcamalpha said:
Good point! So I guess the reason heavier cars/trucks typically take longer to stop in reality is the ability of the braking system to absorb heat. How much can be absorbed, how quickly etc. Also the deceleration isn't constant for the duration of the stopping distance etc etc.
Well I think I'm right about this anyway although hey apparently I do not have the intellect or education to match others at age 10 nevermind now. wink

As I understand things, if the brakes have enough capacity to keep within their working temperature range then mass doesn't come into it. Heavier cars and trucks don't tend to be on performance tyres so aren't likely to brake as well as something sporty and light but just as a very broad stroke, the braking distances SportAuto had for the gt4 (1400ish kg), 991.1rs (1480kg), and 918 (1650kg) were all broadly the same, cup 2s of some N spec on all.