Oh I know but what I'm saying is 280mm with good pads would be fine IMO, its a Clio not an escos or sierra remember. 300mm for show 280mm if that is all that can be done.
I've got a set of AP four pots kicking about doing nothing...
Lol at that answer, nothing to do with power.
Ive driven lighter cars on bigger brake setups, and its been correctly matched to the job, 305mm disks on a 400bhp 900kg Astra turbo that I mapped for example. When he tried with 288mm disks beforehand they were nowhere coping and would warp in a single session, when you are putting 400bhp of energy into a car for 30-50% of the lap and only have 10% of the lap to take it out again, it quickly results in the temperature of the disks getting too high.Try your 300mm setup and you'll realise it is overkill for a one ton car.
FLOL!Cossy = heavy car. Clio = light car, four pots don't put as much heat into the disk for a start as you have to brake lighter for the same effect
Well based on the way you think about things (ie without the most basic of understanding of the laws of physics, such as "energy cannot be created or destroyed merely transformed from one form to another" then I can understand why you would think that.hence I think 280mm with four pots will be fine.
Yes if your brakes arent big enough to convert the kinetic energy into heat energy fast enough to still slow the car down in the same amount of distance then you need to brake sooner to still get down to the same speed, but what that means is that they are now working flat out for longer, which means they raise the temperatures of the disks by more, thats EXACTLY the problem that I have on 280mm disks on my turbo, Im on the brakes so hard for so long that the 280mm disks just cannot act as a big enough reservoir for that amount of energy, so their temperature elevates beyond the point that the material can cope with.Irrelevant if its 20mph faster at a braking point like your saying etc etc then you brake earlier as its carrying more speed, simple no?!?
WTF?
Nothing to do with power?
Its a REALLY simple process mate, the engine puts energy into the car on the straights, the brakes need to then take it back out at the end of the straight before the corners, I cannot understand how you cant grasp something that basic, the more energy you put in on the main part of the straight with the engine the more you have to take out again at the end. Literally joule for joule, its a straight transaction.
Then once the energy has been taken out of the process as heat into the disk, it then has to lose that heat before it can absorb more, or it gets too hot and warps the disk. (exactly what mine does on 280mm, the brakes actually work very well but in one day on track will warp and I dont want to have to buy a new set of disks every time I go on track)
Ive driven lighter cars on bigger brake setups, and its been correctly matched to the job, 305mm disks on a 400bhp 900kg Astra turbo that I mapped for example. When he tried with 288mm disks beforehand they were nowhere coping and would warp in a single session, when you are putting 400bhp of energy into a car for 30-50% of the lap and only have 10% of the lap to take it out again, it quickly results in the temperature of the disks getting too high.
FLOL!
You really dont even understand physics to a GCSE level do you? The energy of the car has to be converted into heat for the car to slow down, the same amount of heat needs to be generated in friction wether its a 4 pot or a single pot thats doing the clamping. Where do you think the extra energy from the cars momentum goes on a 4 pot?
Sure the calipers being larger and ally will dissipate the share going into the pads a little more quickly which helps with things like not boiling brake fluid but that doesnt significantly change the amount of heat that the disks have to absorb.
Well based on the way you think about things (ie without the most basic of understanding of the laws of physics, such as "energy cannot be created or destroyed merely transformed from one form to another" then I can understand why you would think that.
Yes if your brakes arent big enough to convert the kinetic energy into heat energy fast enough to still slow the car down in the same amount of distance then you need to brake sooner to still get down to the same speed, but what that means is that they are now working flat out for longer, which means they raise the temperatures of the disks by more, thats EXACTLY the problem that I have on 280mm disks on my turbo, Im on the brakes so hard for so long that the 280mm disks just cannot act as a big enough reservoir for that amount of energy, so their temperature elevates beyond the point that the material can cope with.
Basic newtonian kinetic energy
Ek = 0.5 * M * V * V
So if you have a car of mass 1000kg and it is going to enter a corner at 80mph (35.8 metres per second) then you need to enter that corner with a total energy of:
0.5 * 1000 * 35.8 * 35.8 = 640820 Joules = 0.641 MJ
Now if we are doing 90mph (40.2 metres per second) before we brake for that bend than we have:
0.5 * 1000 * 40.2 * 40.2 = 808020 = 0.808 MJ
And if we are doing 110mph (49.2 metres per second) then we have:
0.5 * 1000 * 49.2 * 49.2 = 1210320 = 1.21 MJ
So at 90mph approach to an 80mph bend we need to convert .808 - 0.641 = 0.167 MegaJoules of kinetic energy into heat
And at 110mph we need to convert 1.21 - 0.641 = 0.569 MegaJoules of energy
So in fact we can see that in our (heavily over simplified I must confess, ignored drivers weights and rounded to only 3SF etc) example of camp corner at combe comparing my car and my mrs car we find that I need to put 3.4 times more energy into the brakes than she does as heat.
Just to show you what I mean about the weight effecting energy carried and speed attained etc:
A 1400kg escort with 300bhp I know from personal experience will be doing approx 100mph (44.7 m/s) on the approach to the same corner
0.5 * 1400 * 44.7 * 44..7 = 1398663 = 1.40 MJ of energy
It will also take the bend at approx 80mph, so can carry:
0.5 * 1400 * 35.8 * 35.8 = 877100 Joules = 0.877 MJ
So the escort needs to lose 1.40 - 0.877 = 0.523 MJ
So as you can see in that example the braking requirements of the escort and the clio are in fact almost identical, and if anything its in fact the clio that needs very marginally more if anything, although we are talking such a minor difference that its best not to be considered too signfiicant due to the inherently rushed nature of my calculations having minor rounding errors and some assumptions rather than exact real world data etc.
Hope that helps you understand brakes a little mate
I learn more from that post then in all my science lessons at school lol. Didn't know the science of braking was so in depth
That is the golden rule for a trackday car. The more power you have, the bigger the brakes you require.I just thought the more power the bigger the brakes regardless of car size
Lol at the answer again, no need to go so in depth. I understand that energy doesn't disappear but is transformed into other energy, noise, heat. Newtons law of every gorse has an e
PS I never said anything about a Clio with 300bhp versus an escort with 300bhp which is your argument. I am speaking about weight and simply that, two cars irrelevant of power the Clio has less work to do in braking.
The formula renaults have tiny brakes compared to their f4r Clio counterparts?
The formula renaults have tiny brakes compared to their f4r Clio counterparts?
That statement simply makes no sense at all, as demonstrated power is the key factor so trying to spec brakes while ignoring power is never going to work on weight alone. You may as well try and spec based on the colour of the car. Flol
Exactly they weigh less, go faster and hold higher cornering speeds but still do with smaller brakes.
But chip will argue that 3.1444444444 to the power of ten will leave joules (that's Jims sister) with a sore big toe due to the higher pedal exertion applied. Childish, yes but no need to beso pedantic.
A standard clio and a standard escort both entering a braking zone at 100mph, would mean that one of two things was true:Makes perfect sense, that was my initial statement and you started bringing even powered cars with different weights and lower corner entry speeds into things. Explain how a standard Clio doesn't have to do less braking than a standard escort given that they both enter the same braking zone at 100mph and have to achieve the same speed by the same apex of the same corner and have the same co effiecient of drag but the only differing thing is weight?
So maybe you should focus on higher cornering speeds and aero, you might not need 300mm discs then
You Chip sir are a genius.
You Chip sir are a genius.
I tried to help with pictures and information to fit 197/225 brembos under a 15" oz f1 originally and then passed on information from actual experience of how my brakes were more than sufficient with standard pads and yours would suffice with a better pad on my setup.
You then went off on a tangent when I suggested it was a Clio you were specing and not a Escos or Sierra like you referenced in this thread and you usually reference in most threads. You started saying Escorts need different brakes because power not because weight as its a track car and not a road car and just generally over complicating a simple situation.
I said 280mm 4pots would suffice as simple as that you disagreed and threw maths at it.
You have an answer for everything
Using logic with how much excess of braking I have in my car and adding that to a better friction material I would say its more than enough to suit your car.
For my mrs car I think that the 4 pots and 280 would be fine, in fact standard calipers are good enough, but I'd like the later braking points a 4 pot can offer me by putting the same amount of energy into the disks at a faster rate mainly due to a larger pad area.You originally said you were looking for a setup to go under 15" oz f1's, i gave you my info then you said that you were looking for a setup for your missus car as you seem to have figured out a solution for yours on 300mm disks albeit not a very good one with huge spacers and no clearance. So the reference to my car is more than useful for your brief, overkill Infact on a track car and all on 280mm disks.
No question he's a clever cookie, I don't doubt him that for one minute but why....every time there's a simple answer does there have to be a long winded mathematical equation that has little to no importance.
Some very interesting replies there Chip. I for one would be extremely interested in your findings if you were to go into more detail between 280mm and 300mm discs!
My only issue here is the idea that a larger disk will somehow manage heat better.
Can you please explain that statement, or more to the point why you think its correct, as I am struggling to picture in what way you think that having a larger disk will mean it takes longer to cool down the same amount of energy?All a larger disk will do is take longer to cool down between braking.
How do you suggest we increase the surface area relative to its volume?A disk with a larger surface area relative to its volume would work better, be it 300mm, 280mm or 4,000mm.
If the 300mm disk and the 280mm disk are the same width then that's fine.
the 300mm disk would provide better cooling than the 280mm disk. You mentioned previously that a thicker 280mm would be better than a thinner one, since it could store more heat, but that's just not the case. If anything you'd lose breaking ability because it wouldn't cool down as quickly.
The problem with thinner disks as a way of increasing the volume of surface area to weight, is that you are improving the ratio by dropping the weight not by increasing the surface area, and for an application like mine where at the end of the main straight at bedford where im going from 150mph to probably 90mph or so (depending on conditions and how naughty a line I take through the chicane) that is a LOT of energy that has to be absorbed before there is a chance for the disk to dissipate much, while the disks DO lose a small amount of heat during braking, they lose far more after the braking has stopped as its such a small percentage of the time you are actually braking, so you need to think about how much energy just one big application of the brakes is putting in when deciding on the minimum weight that you can cope with.increasing surface area to volume is easy, thinner disks or drilled. But with drilled disks we get into the whole "cracking argument".
Get ali bells and seperate discs for even better disapation.