Nurburgring - hard on brakes / tyres?
Discussion
AJI said:
What if then, you had a massive braking zone and only slightly pressed the brakes so that there was minimum contact and 99% of the braking was acheived by resistances via engine braking, wheel bearings, drag etc.
Brake temps wouldn't get very high due to pad-to-air cooling and also disc-to-air cooling. (Ignore brake fluid .... if you put in a fluid which didn't have any moisture and you had hose lines which were in-affected by pressures involved in either of these situations - so 'boiling' your brakes was not an issue).
This is surely not going to cause as much brake wear as a last second stamp on the pedal to rub off all the speed at the very end is it?
If you didn't use brakes at all you'd eventually come to a stop anyways, resulting in zero brake wear. You'd end up with a braking zone purely from engine and other resistant factors.
So if you're going from zero brake wear from a long braking zone to 'a value of' brake wear to a shorter braking zone then this surely must mean that brake wear increases with the shorter braking zone.
That's true, you would get hardly any brake wear if you use the engine to slow down. But you'd be the slowest car on track and not improving your ability in any way. Brakes are for slowing down and engines are for speeding up. Best keep it that way.
As has been explained on here several times, (based on using only your brakes for slowing down) you will get less wear and less heat on shorter, harder braking inputs. Your opinion may differ, but you can't argue with the fact.
The NS is not particularly heavy on brakes in comparison to UK circuits. In the 24hr race last year we used 2 sets of pads.
jacobyte said:
What if then, you had a massive braking zone and only slightly pressed the brakes so that there was minimum contact and 99% of the braking was acheived by resistances via engine braking, wheel bearings, drag etc.
Brake temps wouldn't get very high due to pad-to-air cooling and also disc-to-air cooling. (Ignore brake fluid .... if you put in a fluid which didn't have any moisture and you had hose lines which were in-affected by pressures involved in either of these situations - so 'boiling' your brakes was not an issue).
This is surely not going to cause as much brake wear as a last second stamp on the pedal to rub off all the speed at the very end is it?
If you didn't use brakes at all you'd eventually come to a stop anyways, resulting in zero brake wear. You'd end up with a braking zone purely from engine and other resistant factors.
So if you're going from zero brake wear from a long braking zone to 'a value of' brake wear to a shorter braking zone then this surely must mean that brake wear increases with the shorter braking zone.
That's true, you would get hardly any brake wear if you use the engine to slow down. But you'd be the slowest car on track and not improving your ability in any way. Brakes are for slowing down and engines are for speeding up. Best keep it that way.
As has been explained on here several times, (based on using only your brakes for slowing down) you will get less wear and less heat on shorter, harder braking inputs. Your opinion may differ, but you can't argue with the fact.
The NS is not particularly heavy on brakes in comparison to UK circuits. In the 24hr race last year we used 2 sets of pads.
sorry but you are missing the point entirely; nobody is suggested going slower than your ability allows on track, it is purely an example to illustrate a point.
and where do you ascertain the above statement from too, it has NOT been explained on here that shorter braking distances gives less wear, if anything it has been deduced that heat is a product of loss of potential energy which is the same in both cases.
molydood said:
nobody is suggested going slower than your ability allows on track, it is purely an example to illustrate a point.
Indeed, but the point being illustrated is irrelevant, as it's not a direct comparison.
molydood said:
it has NOT been explained on here that shorter braking distances gives less wear
Not specifically, but several notes about braking harder for less time give that result. E.g:
francisb said:
furthermore the pad is in contact for less time so you transfer less heat from the disk to the pads/fluid.
and here:
fergus said:
The total amount of heat generated will be similar, however, the rate of change of heat will be different. The subsequent rate of transfer of this heat to other components in a *shorter* space of time normally results in the other braking components not suffering from the effects ofheat transfer, i.e 'heat soak', as badly as the gradual application of heat.
and here:
gutmann pug said:
Hitting the brakes hard and for a short period of time will give less wear than a long comfort braking style
Your experience may differ, but I would be surprised. It would be interesting to conduct a scientific study in real life and measure the true difference.
quote=molydood]nobody is suggested going slower than your ability allows on track, it is purely an example to illustrate a point.
Indeed, but the point being illustrated is irrelevant, as it's not a direct comparison.
[/quote]
The point whereby a small amount of brake application is indeed a direct comparison, allowing the enigne and other reistances to act as 99% of the braking effort. The point whereby 100% of the braking force is applied via engine braking and other forces may not be a direct comparison I accept. But the point I was trying to make is that with these other resistant forces acting over a longer period this will aid the braking effort and reduce the wearing on pads/discs with a longer braking zone. It also allows more time for disc-to-air and pad-to-air cooling.
[quote=francisb] furthermore the pad is in contact for less time so you transfer less heat from the disk to the pads/fluid. [/quote]
As it got pointed out to me earlier - the above statement is unture... the total heat generated will be the same in all cases if the car is reducing from one certain speed to another. (Consercation of energy)
[quote=fergus]The total amount of heat generated will be similar, however, the rate of change of heat will be different. The subsequent rate of transfer of this heat to other components in a *shorter* space of time normally results in the other braking components not suffering from the effects ofheat transfer, i.e 'heat soak', as badly as the gradual application of heat.[/quote]
I'm mot sure this quote can be taken as fact unless there is data to support this. If the total heat produced in each case is the same then I'm guessing brakes/fluid will reach similar temps... only the shorter braking zone will reach higher temps quicker. An conversly the longer braking zone will rech a lower temp for a longer period of time. (but as pointed out, longer period for cooling)
[quote=gutmann pug]Hitting the brakes hard and for a short period of time will give less wear than a long comfort braking style[/quote]
Well its this point which we are indeed discussing.
I'm finding this topic fairly interesting. Being a racing driver you develop your own technique when on track, this is after trying out loads of different variables when you're learning.
There is no question that leaving your braking to the last point and having the shortest braking zone provides you with the quickest lap time (assuming you're maxing out on all the other elements of a good lap), but the physics behind it all is always a learning curve for me. One which I like to argue out as best I can so that you get the full picture of what's happening.
(This is what a discussion forum is all about is it not?)
;-)
>> Edited by AJI on Sunday 23 April 19:44
>> Edited by AJI on Sunday 23 April 19:44
Indeed, but the point being illustrated is irrelevant, as it's not a direct comparison.
[/quote]
The point whereby a small amount of brake application is indeed a direct comparison, allowing the enigne and other reistances to act as 99% of the braking effort. The point whereby 100% of the braking force is applied via engine braking and other forces may not be a direct comparison I accept. But the point I was trying to make is that with these other resistant forces acting over a longer period this will aid the braking effort and reduce the wearing on pads/discs with a longer braking zone. It also allows more time for disc-to-air and pad-to-air cooling.
[quote=francisb] furthermore the pad is in contact for less time so you transfer less heat from the disk to the pads/fluid. [/quote]
As it got pointed out to me earlier - the above statement is unture... the total heat generated will be the same in all cases if the car is reducing from one certain speed to another. (Consercation of energy)
[quote=fergus]The total amount of heat generated will be similar, however, the rate of change of heat will be different. The subsequent rate of transfer of this heat to other components in a *shorter* space of time normally results in the other braking components not suffering from the effects ofheat transfer, i.e 'heat soak', as badly as the gradual application of heat.[/quote]
I'm mot sure this quote can be taken as fact unless there is data to support this. If the total heat produced in each case is the same then I'm guessing brakes/fluid will reach similar temps... only the shorter braking zone will reach higher temps quicker. An conversly the longer braking zone will rech a lower temp for a longer period of time. (but as pointed out, longer period for cooling)
[quote=gutmann pug]Hitting the brakes hard and for a short period of time will give less wear than a long comfort braking style[/quote]
Well its this point which we are indeed discussing.
I'm finding this topic fairly interesting. Being a racing driver you develop your own technique when on track, this is after trying out loads of different variables when you're learning.
There is no question that leaving your braking to the last point and having the shortest braking zone provides you with the quickest lap time (assuming you're maxing out on all the other elements of a good lap), but the physics behind it all is always a learning curve for me. One which I like to argue out as best I can so that you get the full picture of what's happening.
(This is what a discussion forum is all about is it not?)
;-)
>> Edited by AJI on Sunday 23 April 19:44
>> Edited by AJI on Sunday 23 April 19:44
AJI said:
furthermore the pad is in contact for less time so you transfer less heat from the disk to the pads/fluid.
As it got pointed out to me earlier - the above statement is unture... the total heat generated will be the same in all cases if the car is reducing from one certain speed to another. (Consercation of energy)
this is getting painful
. it was me who told you that and it is not contradictory. The DISK is the heat sink; this is where you want the heat to go. pads have a MUCH lower thermal conductivity, in other words when the pad and disk surfaces touch friction turns the kinetic energy of the car into heat. the vast majority of that heat 'goes into' (sorry not very technical) the disk because it has higher thermal conductivity. the pad will heat up eventually - the longer it is left in contact with the disk the hotter it will get up to the temperature of the disk, eventually you heat up the cylinders/calipers and brake fluid. energy is conserved. its just preferable to do the conserving in the disk >> Edited by francisb on Sunday 23 April 20:39
AJI said:
Being a racing driver you develop your own technique when on track, this is after trying out loads of different variables when you're learning.
I quick look at any of the data log traces from, say, a touring car will illustrate their braking technique pretty well. I think you'll find that other than the effect of trail braking into a corner, their techn iques may well be pretty consistent - as this is often the result of various techniques to find the quickest lap time....
francisb - so what your saying is that during a longer braking zone even though the same amount of heat is generated as with a shorter braking zone, its the pads which are getting hotter in this case due to the fact that the lower temp generated in the disc (as opposed to the higher temp in the other situation) is transferring over to the pads due to the longer time invlolved in contact?
I'm not trying to dis-respect your point here, I'm just trying to get it sorted in my head.
I agree that the disc will be the heat sink and will dissapate heat to the air at a much faster rate than any of the other components involved in the brakes due to the vents.
I agree that the pads are in contact longer.
Do you agree that the temperature magnitude generated in the dics in the shorter braking zone is higher?
If this is the case then a higher temp magnitude will cause higher heat transfer rate from disc to pad will it not? Or is it a property of the thermal conductivity of the pad which prevents this?
But I think I may be straying from the original question. It was about brake wear and not how heat is transfered to fluid and other components.
I see brake wear to be loss of material within the disc and pads (ie. when you stop and let it cool your fluid returns back to how it was before braking - on a completely closed/sealed system,.... but you can't replace pad/disc material without buying new compnents). So eliminating fluid effects for this point of the argument... I still think that pad and disc wear would be determined as to how they wear at different temp magnitudes. And I'm guessing that pads and discs wear at faster rate at higher temps than they do at lower temps. This is purely a guess because I have no data to back this up. But if my assumption is true then this supports the longer braking zone to be better for pad/dics wear rate.
I'm not trying to dis-respect your point here, I'm just trying to get it sorted in my head.
I agree that the disc will be the heat sink and will dissapate heat to the air at a much faster rate than any of the other components involved in the brakes due to the vents.
I agree that the pads are in contact longer.
Do you agree that the temperature magnitude generated in the dics in the shorter braking zone is higher?
If this is the case then a higher temp magnitude will cause higher heat transfer rate from disc to pad will it not? Or is it a property of the thermal conductivity of the pad which prevents this?
But I think I may be straying from the original question. It was about brake wear and not how heat is transfered to fluid and other components.
I see brake wear to be loss of material within the disc and pads (ie. when you stop and let it cool your fluid returns back to how it was before braking - on a completely closed/sealed system,.... but you can't replace pad/disc material without buying new compnents). So eliminating fluid effects for this point of the argument... I still think that pad and disc wear would be determined as to how they wear at different temp magnitudes. And I'm guessing that pads and discs wear at faster rate at higher temps than they do at lower temps. This is purely a guess because I have no data to back this up. But if my assumption is true then this supports the longer braking zone to be better for pad/dics wear rate.
AJI said:
francisb - so what your saying is that during a longer braking zone even though the same amount of heat is generated as with a shorter braking zone, its the pads which are getting hotter in this case due to the fact that the lower temp generated in the disc (as opposed to the higher temp in the other situation) is transferring over to the pads due to the longer time invlolved in contact?
correct
AJI said:
Do you agree that the temperature magnitude generated in the dics in the shorter braking zone is higher?
yes but i think for different reasons than you. again assuming same change in velocity.
1st reason. the disc is radiating and convecting heat to the air, if you brake for longer it is cooling for longer.
2nd reason. the disk is conducting and radiating heat to the pads, the longer you brake the more energy you transfer to the pads.
HOWEVER over the same TIME period the harder braking cars disks will be cooler because they are cooling whist im still waiting for you to slow down
AJI said:
But if my assumption is true then this supports the longer braking zone to be better for pad/dics wear rate.
no thats true anyway because you're not braking as hard, ie the pad isnt being clamped onto the disk with as much force.
the point is on track i'd suggest the primary problem is fluid boiling not disks getting too hot.
>> Edited by francisb on Monday 24th April 11:07
Jacobyte, I hope that didn't come across agressive, it wasn't meant to be. My point still stands, in my opinion it has not yet been explained that pad wear is better with either method, although if you add up the collective *comments* then this conclusion could be drawn if we assume all the comments are valid/correct. I personally do not agree with some, therefore I am still open to discuss and understand this further
AJI, Francisb, interesting reading, I had not considered the thermal conductivity of the disc being greater than the pad, and that may well be a factor. However, I still support the view given in my first post as the biggest factor; in that it comes down to how the characteristics of the pad change at different temps. I think if we could get some info on that it would be interesting.
AJI, Francisb, interesting reading, I had not considered the thermal conductivity of the disc being greater than the pad, and that may well be a factor. However, I still support the view given in my first post as the biggest factor; in that it comes down to how the characteristics of the pad change at different temps. I think if we could get some info on that it would be interesting.
check out www.braketechnology.com/techinfo.html for info on mju (friction) characteristics of various pagid pads as a function of operating temperature. Apologies, but I'm not sure about the wear characteristics as a function of heat. This also highlights the fact that some pads NEED heat in them to 'work' (i.e. generate any friction). To do this, they need to be stood on hard to generate the heat (i.e. no gentle braking). PF seem to do some pads that operate at 2000 degrees F (PFC 01)! www.stoptech.com/products/high_performance_pads.shtml (bottom of page). As well
as various friction characteristics, all the various pads have different 'initial bite' and ease of modulation and release characteristics..... More of a dilemma than purely how hot they get!
Should you not treat pads as a consumable, the same way tyres are treated? I understand the initial question, I'm just curious as to how relevant it is!
>> Edited by fergus on Monday 24th April 13:40
as various friction characteristics, all the various pads have different 'initial bite' and ease of modulation and release characteristics..... More of a dilemma than purely how hot they get!
Should you not treat pads as a consumable, the same way tyres are treated? I understand the initial question, I'm just curious as to how relevant it is!
>> Edited by fergus on Monday 24th April 13:40
molydood said:
Jacobyte, I hope that didn't come across agressive, it wasn't meant to be. My point still stands, in my opinion it has not yet been explained that pad wear is better with either method, although if you add up the collective *comments* then this conclusion could be drawn if we assume all the comments are valid/correct. I personally do not agree with some, therefore I am still open to discuss and understand this further
Not at all: aggressive would be sending me a threatening PM, as I received from another forum this morning. Bit of a surprise that one, but the culprit has since apologised after I wagged my finger back at him
. Back to this thread hijack...
With regard to brake wear, my own experience has demonstrated that hard/short braking improves pad longevity compared to braking not so hard but over a greater distance. The descriptions throughout this thread are merely explaining why that is the case.
The examples I shall use below are only personal anecdotal evidence, but of course a scientifically calibrated test would be more meaningful:
I am far from being a great racing driver, but have enjoyed some success and have been an instructor for some teams and circuits. I brake very late and progressively very hard, cadencing on the threshold as necessary.
I use Greenstuff pads on my road Integrale and frequent Lancia trackdays for fun. Other owners of this car feel that Greenstuff pads overheat too quickly and only last for half a trackday, so most use Red/Yellowstuff. I agree with them that Greenstuff pads do not last long, but I do about 2 trackdays a year plus 2 weekends at the Ring. The car does abot 5000 road miles a year. I need one set of pads a year.
I bought my Alfa 147 brand new. It didn't need new pads until 42,000 miles, which is rather better than the average, particularly as it did a trackday when it was 3 days old
. Hope that helps.
yep, that is interesting, and I would not want to dissagree that the hard fast approach is easier on the pads, but it is purely in the area of validation where I may be inclined to take it further. I know a lot of posts have supported the hard/fast approach, and those views have the advantage of being in line with observation, but it doesn't make those explanations correct. It doesn't necessarily make them any more correct than ones *not* in line with observation, after all, the world was flat until somebody looked boyond the observations... 
molydood said:
also, did you manage to run your Alfa engine in with just 3 days of ownership?
Or did you do that on the track?
Run in? What's that? It had 170 miles on the clock by the time I had reached Donington Park
Alfa Romeo are said to run in engines on the bench before installing them into cars. Not sure if that's actually true, but at the time I was (perhaps foolishly) more than happy to believe it!
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