PCCB out braked the steels last night on 5th gear.
Discussion
isaldiri said:
The whole point is that you are not necessarily braking at the same force for a heavier car.
And you bloody well can lock a tyre easily above 70mph. Braking for stowe down hangar straight at 140+ on a rs or even at 150+ on a Mclaren, with enough shove ABS will trigger very quickly and in no way only at 60/70mph as you are claiming which is below the minimum apex speed of stowe in one of those cars anyway..
I picked a 60/70 mph figure out the air as it's down to grip levels and tyres. In the rain you can trigger ABS at 150 I guess.And you bloody well can lock a tyre easily above 70mph. Braking for stowe down hangar straight at 140+ on a rs or even at 150+ on a Mclaren, with enough shove ABS will trigger very quickly and in no way only at 60/70mph as you are claiming which is below the minimum apex speed of stowe in one of those cars anyway..
you are braking at the same force as that's all your brakes can provide !! then you have to remove pressure when the brakes over come friction at what speed this is on any said car be it 60mph to 100mph, it's def not at 160 mph on hanger straight when you 1st press them.
go do a race school course, you will find you cannot lock a wheel at high speed and the skill in corner entry is ALL about threshold braking once you have scrubed some speed off.
on track I never see a ABS light ! and I do notice I take yards out of other cars on track in corner entry. that's why driving a manual demands a much higher degree of skill to lap fast, track driving is pretty basic, it's straights and bends ALL track time gained is under brakes at a certain skill level and if you know the fastest line that's that. Corner entry is key, every thing else just happens imo.
. The point is to understand''
hunter 66 said:
ABS , try race a car without it , then Braking especially into corners becomes an issue .......
that's the skill in lapping fast if you read my post above.A highly skilled driver can threshold brake to a high degree of accuracy avoiding the ABS system or in a car without ABS avoid a lock up, watch F1 they manage ok ;-)
But F1 is a case in point, at 200 mph they are not locking a tyre down the straights under brakes, once the force over comes the grip you see F1 cars lock the unloaded wheel at the lower speeds.
lapping fast is all corner entry, we have talked about this before, you think it's all corner exit. but that's a by product of entry.
hence you see a lot of people over take under brakes to then get repasted straight away out the bend.
There is only 1 fastest line and there is only one braking point, get either wrong and you do a slower lap time !
Porsche911R said:
I picked a 60/70 mph figure out the air as it's down to grip levels and tyres. In the rain you can trigger ABS at 150 I guess.
you are braking at the same force as that's all your brakes can provide !! then you have to remove pressure when the brakes over come friction at what speed this is on any said car be it 60mph to 100mph, it's def not at 160 mph on hanger straight when you 1st press them.
Well that's not a surprise you pick numbers out 8f the air.you are braking at the same force as that's all your brakes can provide !! then you have to remove pressure when the brakes over come friction at what speed this is on any said car be it 60mph to 100mph, it's def not at 160 mph on hanger straight when you 1st press them.
Fair enough I agree I might not be triggering abs at 150 immediately but I am certain it's well above 100mph.
I'll ask this again, if mass is so important in braking why does a sports bike which has a massive advantage in acceleration over a sports car have pretty much no advantage in braking over the car?
Porsche911R said:
go do a race school course, you will find you cannot lock a wheel at high speed and the skill in corner entry is ALL about threshold braking once you have scrubed some speed off.
on track I never see a ABS light ! and I do notice I take yards out of other cars on track in corner entry. that's why driving a manual demands a much higher degree of skill to lap fast, track driving is pretty basic, it's straights and bends ALL track time gained is under brakes at a certain skill level and if you know the fastest line that's that. Corner entry is key, every thing else just happens imo.
Fk me I'm really keen to see you at Spa next year banging out easy 2:40/41 laps in your GT3 given it's so basic....on track I never see a ABS light ! and I do notice I take yards out of other cars on track in corner entry. that's why driving a manual demands a much higher degree of skill to lap fast, track driving is pretty basic, it's straights and bends ALL track time gained is under brakes at a certain skill level and if you know the fastest line that's that. Corner entry is key, every thing else just happens imo.
Porsche911R said:
that's the skill in lapping fast if you read my post above.
A highly skilled driver can threshold brake to a high degree of accuracy avoiding the ABS system or in a car without ABS avoid a lock up, watch F1 they manage ok ;-)
But F1 is a case in point, at 200 mph they are not locking a tyre down the straights under brakes, once the force over comes the grip you see F1 cars lock the unloaded wheel at the lower speeds.
More bloody gibberish plucked out of the air. F1 cars have literally tons of downforce at high speed that allows them to brake extraordinarily hard so you really cannot lock the brakes at high speeds on an aero car.A highly skilled driver can threshold brake to a high degree of accuracy avoiding the ABS system or in a car without ABS avoid a lock up, watch F1 they manage ok ;-)
But F1 is a case in point, at 200 mph they are not locking a tyre down the straights under brakes, once the force over comes the grip you see F1 cars lock the unloaded wheel at the lower speeds.
If you think in a race, even a dry one, that a non abs car is going to be competitive with one with abs you are deluded. The driver can make a difference for one or even a couple of corners. For consistency over a race distance not a bloody chance. Maybe you can I suppose since track driving is so easy as you claim.....
I'll ask this again, if mass is so important in braking why does a sports bike which has a massive advantage in acceleration over a sports car have pretty much no advantage in braking over the car?
This may help... https://www.redbull.com/gb-en/motogp-repsol-honda-...
Edited by jh001 on Wednesday 20th November 13:36
isaldiri said:
accurate if your braking force remains the same for a heavier car. It does not for the purposes of earlier example as the car slows at the force of friction from tyre to road....
KE = 0.5 mv^2 = force x distance = work done to stop the car.
Force being coefficient of friction x mass x gravitational acceleration.
Mass cancels on both sides of the equation.
I'm all ears if someone can disprove the above btw as well.
On the above equation, kinetic energy is not dissipated by the tyres, so that doesn't really work. KE = 0.5 mv^2 = force x distance = work done to stop the car.
Force being coefficient of friction x mass x gravitational acceleration.
Mass cancels on both sides of the equation.
I'm all ears if someone can disprove the above btw as well.
Mass does provide some more tyre friction grip, but it doesnt give you any more braking friction force. And whilst increased mass does increase available tyre grip force, it's not normally linear with increasing mass, so as you gain mass, you typically lose relative grip.
In your arguement, there is spare brake capacity in the lighter case, and you can apply more brake force in the heavier case.
However if you are not able to use the full brake capacity in the lighter case due to limited tyre friction, then in the heavier case, yes you can apply more brake pressure without locking up but this is just shedding the extra energy from the extra mass - you won't stop in the same distance as your grip force relative to vehicle mass has decreased. You will also end up overwhelming the brake system sooner.
The only way your argument works is with tyres that give a linear increase in grip force with vertical force, and a braking system with sufficient spare capacity in the lighter case at the speed you're at and the deceleration rate you require.
skinny said:
On the above equation, kinetic energy is not dissipated by the tyres, so that doesn't really work.
Mass does provide some more tyre friction grip, but it doesnt give you any more braking friction force. And whilst increased mass does increase available tyre grip force, it's not normally linear with increasing mass, so as you gain mass, you typically lose relative grip.
In your arguement, there is spare brake capacity in the lighter case, and you can apply more brake force in the heavier case.
However if you are not able to use the full brake capacity in the lighter case due to limited tyre friction, then in the heavier case, yes you can apply more brake pressure without locking up but this is just shedding the extra energy from the extra mass - you won't stop in the same distance as your grip force relative to vehicle mass has decreased. You will also end up overwhelming the brake system sooner.
The kinetic energy is dissipated as heat somewhere whether brakes/tyres/etc though? And the tyres are the interaction with the road that actually does stop the car.Mass does provide some more tyre friction grip, but it doesnt give you any more braking friction force. And whilst increased mass does increase available tyre grip force, it's not normally linear with increasing mass, so as you gain mass, you typically lose relative grip.
In your arguement, there is spare brake capacity in the lighter case, and you can apply more brake force in the heavier case.
However if you are not able to use the full brake capacity in the lighter case due to limited tyre friction, then in the heavier case, yes you can apply more brake pressure without locking up but this is just shedding the extra energy from the extra mass - you won't stop in the same distance as your grip force relative to vehicle mass has decreased. You will also end up overwhelming the brake system sooner.
I agree there is an element of tyre load sensitivity but last I looked at one (admittedly for a slick tyre), coefficient of friction of a tyre starts decreasing significantly in large (as in multiples) of vertical load increases. It's possible I accept that on a road tyre say 100kg difference on a 1500kg road car makes a big difference as you are suggesting but I honestly wouldn't have thought it would be that much.
skinny said:
The only way your argument works is with tyres that give a linear increase in grip force with vertical force, and a braking system with sufficient spare capacity in the lighter case at the speed you're at and the deceleration rate you require.
I suppose that is exactly my argument. Within the context of ceramics to steel to stay on topic 
, a 20kg or even 50kg increase in weight of a car isn't going to affect the braking performance of something like a gt3 given both sets of brakes have enough capacity to be tyre limited and that increase in weight isn't enough to sufficiently change the behaviour of the tyre wrt to coefficient of friction.Porsche911R said:
that's the skill in lapping fast if you read my post above.
A highly skilled driver can threshold brake to a high degree of accuracy avoiding the ABS system or in a car without ABS avoid a lock up, watch F1 they manage ok ;-)
But F1 is a case in point, at 200 mph they are not locking a tyre down the straights under brakes, once the force over comes the grip you see F1 cars lock the unloaded wheel at the lower speeds.
lapping fast is all corner entry, we have talked about this before, you think it's all corner exit. but that's a by product of entry.
hence you see a lot of people over take under brakes to then get repasted straight away out the bend.
There is only 1 fastest line and there is only one braking point, get either wrong and you do a slower lap time !
Driving by numbers? Your braking points and lines would be exactly the same over the course of a sprint race or say 3 hour stint? You wouldnt change them? What about adjustable brake bias. Still only 1 fastest line and braking point? A highly skilled driver can threshold brake to a high degree of accuracy avoiding the ABS system or in a car without ABS avoid a lock up, watch F1 they manage ok ;-)
But F1 is a case in point, at 200 mph they are not locking a tyre down the straights under brakes, once the force over comes the grip you see F1 cars lock the unloaded wheel at the lower speeds.
lapping fast is all corner entry, we have talked about this before, you think it's all corner exit. but that's a by product of entry.
hence you see a lot of people over take under brakes to then get repasted straight away out the bend.
There is only 1 fastest line and there is only one braking point, get either wrong and you do a slower lap time !
Love your enthusiasm but I think that with posts like this you are sleepwalking towards planet dilettante
Steve Rance said:
Porsche911R said:
that's the skill in lapping fast if you read my post above.
A highly skilled driver can threshold brake to a high degree of accuracy avoiding the ABS system or in a car without ABS avoid a lock up, watch F1 they manage ok ;-)
But F1 is a case in point, at 200 mph they are not locking a tyre down the straights under brakes, once the force over comes the grip you see F1 cars lock the unloaded wheel at the lower speeds.
lapping fast is all corner entry, we have talked about this before, you think it's all corner exit. but that's a by product of entry.
hence you see a lot of people over take under brakes to then get repasted straight away out the bend.
There is only 1 fastest line and there is only one braking point, get either wrong and you do a slower lap time !
Driving by numbers? Your braking points and lines would be exactly the same over the course of a sprint race or say 3 hour stint? You wouldnt change them? What about adjustable brake bias. Still only 1 fastest line and braking point? A highly skilled driver can threshold brake to a high degree of accuracy avoiding the ABS system or in a car without ABS avoid a lock up, watch F1 they manage ok ;-)
But F1 is a case in point, at 200 mph they are not locking a tyre down the straights under brakes, once the force over comes the grip you see F1 cars lock the unloaded wheel at the lower speeds.
lapping fast is all corner entry, we have talked about this before, you think it's all corner exit. but that's a by product of entry.
hence you see a lot of people over take under brakes to then get repasted straight away out the bend.
There is only 1 fastest line and there is only one braking point, get either wrong and you do a slower lap time !
Love your enthusiasm but I think that with posts like this you are sleepwalking towards planet dilettante
the skills always in corner entry though and that's where the lap time comes from. And for each given lap there would be one best line and one best braking point, that's the skill of the driver to maximize and find out. The rest of track driving is pretty simple and a by product of that.
But in racing, there is the 'they zig, I zag' philosophy. You watch a skilled overtaker (alonso, in his day for example) and they will often weigh up the driver in front and then deliberately use a different line to get past. There can be more than one line.
Moreover, in relation to braking rather than exit speed.
Moreover, in relation to braking rather than exit speed.
- That depends on whether the longer straight is before or after the bend in question
- Exit speed dictates your pace at the end of the next straight
- Slow in, fast out!
Digga said:
Moreover, in relation to braking rather than exit speed.
But it's also bit more nuanced than that isn't it? It depends where you are losing vs gaining time. Especially on racing cars which are drag limited in top speeds so a say 5kmh advantage in exit speed does not carry for the full straight. And if you've compromised your entry or mid corner in order to maximise exit speed, the overall time loss might well not be worth it. - That depends on whether the longer straight is before or after the bend in question
- Exit speed dictates your pace at the end of the next straight
- Slow in, fast out!
Of course the challenge for brakes is always heat management. The thermal energy generated to stop a car is directly related to the mass of the car and to the square of the speed. Carbon/carbon brakes are the best technology at the extremes which is why they are used in F1 and Drag Racing but that does not mean they are needed for road or track cars or for race cars at the lower levels of motorsport. Any brake technology is OK as long as it can manage the heat generated from the usage of the car they are designed for.
I am guessing both the carbon ceramic and steel offerings from Porsche are more than adequate for normal road use even with the GT cars. At what point does a clear performance advantage appear between the Porsche steel and carbon ceramic systems?
I am guessing both the carbon ceramic and steel offerings from Porsche are more than adequate for normal road use even with the GT cars. At what point does a clear performance advantage appear between the Porsche steel and carbon ceramic systems?
Edited by C4ME on Wednesday 20th November 16:46
Porsche911R said:
yes there is only one fastest line and one braking point each lap ;-) ,, that can change every lap, but for the same lap there is ONLY ONE to get the fastest time. it's a given that will change as the mass of the car changes via fuel load and also tyre wear etc etc.
the skills always in corner entry though and that's where the lap time comes from. And for each given lap there would be one best line and one best braking point, that's the skill of the driver to maximize and find out. The rest of track driving is pretty simple and a by product of that.
Bingo. You are starting to work your way towards getting your GCSE. Now all you have to do is to work out why the braking point is never a constant - along with your line and then how that might change with engine layout and other dynamic mechanicalvariables, mix that in with weather etc. and then throw all that into a pot and figure out your fastest line and braking point for each lap to get your A level. Then you've got to translate that into practice and your real learning starts.the skills always in corner entry though and that's where the lap time comes from. And for each given lap there would be one best line and one best braking point, that's the skill of the driver to maximize and find out. The rest of track driving is pretty simple and a by product of that.
I started racing a long time ago. 30 years on, I'm still learning and realise how little I knew back then and how much there still is to learn. If you want to truly learn any art you need to open your mind to the possibility that there is always more to learn and also, a little humility doesnt go amiss on occasion.
Getting back to Ceramic brakes. I know that you have them on your car and that other drivers who have them would like to think that there is a benefit. From personal experience , the advantage on the track is minimal - certainly for the cost. If you are looking at marginal benefit per £ spent there are other less expensive upgrades that will bring much greater performance benefits. I'm not saying that there are absolutely no benefits - but they are marginal.
isaldiri said:
Porsche911R said:
that's the skill in lapping fast if you read my post above.
A highly skilled driver can threshold brake to a high degree of accuracy avoiding the ABS system or in a car without ABS avoid a lock up, watch F1 they manage ok ;-)
But F1 is a case in point, at 200 mph they are not locking a tyre down the straights under brakes, once the force over comes the grip you see F1 cars lock the unloaded wheel at the lower speeds.
More bloody gibberish plucked out of the air. F1 cars have literally tons of downforce at high speed that allows them to brake extraordinarily hard so you really cannot lock the brakes at high speeds on an aero car.A highly skilled driver can threshold brake to a high degree of accuracy avoiding the ABS system or in a car without ABS avoid a lock up, watch F1 they manage ok ;-)
But F1 is a case in point, at 200 mph they are not locking a tyre down the straights under brakes, once the force over comes the grip you see F1 cars lock the unloaded wheel at the lower speeds.
If you think in a race, even a dry one, that a non abs car is going to be competitive with one with abs you are deluded. The driver can make a difference for one or even a couple of corners. For consistency over a race distance not a bloody chance. Maybe you can I suppose since track driving is so easy as you claim.....
You can lock up at any speed if you apply more force than the tyres can take, at lower speeds the aero comes off so its easier to lock up as there's less downforce so less force required. Well that's in my experience of running the radical this year and the skip barber school of racing book. Edited by JayK12 on Wednesday 20th November 16:12
skinny said:
isaldiri said:
accurate if your braking force remains the same for a heavier car. It does not for the purposes of earlier example as the car slows at the force of friction from tyre to road....
KE = 0.5 mv^2 = force x distance = work done to stop the car.
Force being coefficient of friction x mass x gravitational acceleration.
Mass cancels on both sides of the equation.
I'm all ears if someone can disprove the above btw as well.
You're all ears.KE = 0.5 mv^2 = force x distance = work done to stop the car.
Force being coefficient of friction x mass x gravitational acceleration.
Mass cancels on both sides of the equation.
I'm all ears if someone can disprove the above btw as well.
The kinetic energy of the car is determined by its mass and velocity - this gives us a figure in joules
The force required to stop the car is this energy divided by the distance taken to stop - this gives us a figure in newtons.
You don't have an equation, as you don't equate energy and force, as they are not the same thing, therefore the mass is included, both to determine the energy and the force required (the work) to either create it or dissipate it. While there is a principle of conservation of energy, there is not one for force,
Obviously there are other factors but add to the mass and you will either need more force to stop in the same distance or more distance to stop.
The motorcycle will stop more slowly than the car because it has smaller friction surfaces, but if you add a pillion it will take further to stop if the brake force remains the same.
There will be a very complex formula with coefficient of friction, tyre contact patch, temperature, mechanical resistance, air resistance included - but all of it will be determined by mass, which is a key variable and speed, which is the greatest factor.
JulierPass said:
I haven't seen the article as I don't watch 5th gear. However, there is a reason why all of the factory built Porsche Cup Cars and R's have steel brakes. If the advantage was as pronounced as your post suggests then the race would come with ceramics from the factory.
Presume banned due to costsRemoved mine and went steel setup on my track car for same reason.
No comparison now running the cup cars brakes vs the standard PCCB re stopping power
pete.g said:
isaldiri said:
accurate if your braking force remains the same for a heavier car. It does not for the purposes of earlier example as the car slows at the force of friction from tyre to road....
KE = 0.5 mv^2 = force x distance = work done to stop the car.
Force being coefficient of friction x mass x gravitational acceleration.
Mass cancels on both sides of the equation.
I'm all ears if someone can disprove the above btw as well.
The kinetic energy of the car is determined by its mass and velocity - this gives us a figure in joulesKE = 0.5 mv^2 = force x distance = work done to stop the car.
Force being coefficient of friction x mass x gravitational acceleration.
Mass cancels on both sides of the equation.
I'm all ears if someone can disprove the above btw as well.
The force required to stop the car is this energy divided by the distance taken to stop - this gives us a figure in newtons.
You don't have an equation, as you don't equate energy and force, as they are not the same thing, therefore the mass is included, both to determine the energy and the force required (the work) to either create it or dissipate it. While there is a principle of conservation of energy, there is not one for force,
Work done is a figure in joules or it was last time I checked (you might want to disagree here I suppose), that is force x distance and that is what I am equating to kinetic energy. Distance being braking distance obviously and force being tyre coefficient of friction x weight of the car (in newtons).
pete.g said:
Obviously there are other factors but add to the mass and you will either need more force to stop in the same distance or more distance to stop.
The motorcycle will stop more slowly than the car because it has smaller friction surfaces, but if you add a pillion it will take further to stop if the brake force remains the same.
pete.g said:
There will be a very complex formula with coefficient of friction, tyre contact patch, temperature, mechanical resistance, air resistance included - but all of it will be determined by mass, which is a key variable and speed, which is the greatest factor.
As an aside where on earth is fioran0 if slippy or someone else might know? He would (I hope anyway) get the point I have been trying to make and would be able to far better explain it than me.
Edited by isaldiri on Wednesday 20th November 16:12
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