No Brakes!!

[Rotary Junkie]

Yes! +1. Although if I had a choice between turning ABS off and these brake upgrades, I'd take the choice of ABS off first.

But (of course) I want it all: option to turn ABS off, carbon brakes, brake controller, and fade.

The PC sims are calling your name, Parnelli.

 

[robhulme]

The laws of physics, along with brake and tyre manufactures and race engineers and designers the world over disagree with you. So personally I like the company I am in.

As long as your current braking system is capable of locking up your tyres then increasing rotor size and/or fitting more powerful calipers will not stop you quicker. As long as your tyres are locking then they are your limiting factor not your tyres...



Source - http://www.stoptech.com/tech_info/wp_brakebiasandperformance.shtml

and

http://www.stoptech.com/tech_info/The Physics of Braking Systems.pdf

...read the above two and then come back.

BTW - You may also want to know that I have taught the fundamentals of vehicle dynamics within the motor industry for over a decade. This a subject I know a bit about.

Scaff

For the person who said that the brakes do not stop your car the tyres do thanks!.
My boyfriend of 3 years took this info and sold his brakes for his evo 6 ralliart and bought some top of the range pirelli tyres.
On the first and only outing he pressed the brake pedal to find indeed he had made a big mistake trusting the info gained off this forum, He is at this minute in time picking up his curtesy car from the garage.

 

[Scaff]

For the person who said that the brakes do not stop your car the tyres do thanks!.
My boyfriend of 3 years took this info and sold his brakes for his evo 6 ralliart and bought some top of the range pirelli tyres.
On the first and only outing he pressed the brake pedal to find indeed he had made a big mistake trusting the info gained off this forum, He is at this minute in time picking up his curtesy car from the garage.

Seriously is that the best you can come up with?


Scaff

 

[robhulme]

Do you agree with me though that to stop a car you need more than tyres?

 

[Scaff]

Do you agree with me though that to stop a car you need more than tyres?

I think your arguing semantics because at no point have I said that you don't need brakes.

Brakes slow the rotation of the wheel and tyre assembly, however its the tyre/road interface that determines how quickly you slow and stop your car.


Scaff

 

[YellowG1]

There is an option inside the tuning menu to adjust break bias you know. I don't see whats so wrong with just that. I don't have any problems stopping any of my cars.. 745 hp R34 299 HP CIVIC 330 HP S200

👍 Don't know why i assumed for the first two weeks I had the game that brake bias was unchangable. All cars come with a brake balance controller for some reason (didn't you used to have buy this in GT4?). Just dumping using the 5-5 standard bias and changing it to 8-2, 7-3, or 7-4 makes a WORLD of difference in braking power and stability. Though it doesn't replace the fact that you should be able to buy big brakes.

 

[lukey2985]

you brake really fast by hitting a wall =)

 

[Ding]

i think Scaff deserves a medal for his patience. Interesting thread and the sources contained within though. Thanks.

 

[Falango]

Do you agree with me though that to stop a car you need more than tyres?

The argument here was about brake upgrades, not the lack of a braking system all together.

 

[zorrofox]

I was initially perturbed at the lack of brake (it's brake folks, not break!) upgrades but after driving a lot and gradually upgrading the rest of a given cars' performance I'm now thinking the coders have brake power scalability built-in. I mean, as long as I've upgraded the tyres to suit the engine and chassis performance the brakes always seem to be adequate. Am I wrong?

 

[robhulme]

The argument here was about brake upgrades, not the lack of a braking system all together.

In one of scaffs posts he included some infomation on brakes, And in that infomation it clearly states that brakes dont stop you the tyres do.
I believe if u dont have brakes you simply cant stop. Where as If you drove a car just on its rims although been stupid u still could stop the car with use of the brakes.

 

[Scaff]

In one of scaffs posts he included some infomation on brakes, And in that infomation it clearly states that brakes dont stop you the tyres do.
I believe if u dont have brakes you simply cant stop. Where as If you drove a car just on its rims although been stupid u still could stop the car with use of the brakes.

Actually its a quote from a white-paper published by a brake manufacturer called Stop-Tech (the manufacture racing brake systems) and written by a guy called James Walker, he's a bit of info about him....

James Walker, Jr. is currently the supervisor of vehicle performance development for brake control systems at Delphi Energy & Chassis. His prior professional experience includes brake control system development, design, release, and application engineering at Kelsey-Hayes, Saturn Corporation, General Motors, Bosch, and the Ford Motor Company. Mr. Walker created scR motorsports consulting in 1997, and subsequently competed in seven years of SCCA Club Racing in the Showroom Stock and Improved Touring categories.

Through scR motorsports, he has served actively as an industry advisor to Kettering University in the fields of brake system design and brake control systems. In addition, Mr. Walker contributes regularly to several automotive publications focusing on brake system analysis, design, and modification for racing and other high-performance applications. He is a recipient of the SAE Forest R. McFarland Award for distinction in professional development/education. Mr. Walker has a B.S. in mechanical engineering from GMI Engineering & Management Institute.

Source - http://www.stoptech.com/tech_info/wp_jameswalker.shtml

.....now stop taking this in a quite frankly ridiculously literal manner and stop using text speak. Its 'you' not 'u' and the AUP is quite clear on the fact that its not permitted and should you do so again then a formal infraction will be issued.

Also the full quote (which I have posted numerous times) is....

“You can take this one to the bank. Regardless of your huge rotor diameter, brake pedal ratio, magic brake pad material, or number of pistons in your calipers, your maximum deceleration is limited every time by the tire to road interface. That is the point of this whole article. Your brakes do not stop your car. Your tires do stop the car. So while changes to different parts of the brake system may affect certain characteristics or traits of the system behavior, using stickier tires is ultimately the only sure-fire method of decreasing stopping distances.”

Source - http://www.stoptech.com/tech_info/wp_brakebiasandperformance.shtml

...quite clearly talks about the braking system its self, and goes on to explain (in detail) why your brakes do not stop your car, but ultimately its your tyres that do.

Now stop spamming up the thread and actually go and read the information, rather than wasting everyone time.


Scaff

 

[Multipen]

I just want to say that I found this thread very helpful, especially Scaff's posts.

I too was under the impression that it was all about brake upgrades, thanks for clearing that up.


I'm a big formula 1 fan and always assumed that the brakes fitted on those cars were very strong -as in would stop you very quickly.
However after reading this thread I no longer know what kind of brakes are used in F1. Do the brakes differ much from the ones used in road cars, in terms of 'strength' or does the only real difference lie in durability and heat-loss?

 

[Ding]

....I believe if u dont have brakes you simply cant stop. Where as If you drove a car just on its rims although been stupid u still could stop the car with use of the brakes.

The topic is not about whether you need brakes at all to stop, it is obvious that you do and in fact Scaff has already stated that this is not the point, we are discussing whether uprated brake system actually affect stopping distances. You have clearly missed the point by a country mile.

So with your example I think you'll find you will be relying on the grip levels of the rims to stop instead of tire grip. The same physical processes are still at work, ie "wheel material" to road interface dictating the stopping distance. The brakes would still lock up regardless, in fact easier due to the massively reduced levels of grip now found with the wheel rims instead of rubber tires.

Maybe its our fault for assuming that wheels have tires in most of the situations and setups we have discussed, I don't know, but either way your reply has done nothing to derail Scaff's responses and explanations. I think it wise for you to follow Scaff's suggestion of reading the sources and trying to understand what is actually being debated here.


Whilst I am here I might ask a question to those who have spent some time on GT5 and tuned some cars (I have a copy, but have just moved house and yet to set my wheel up and play). It was mentioned earlier about braking performance changing when the car is "in" or "out" of aero, is this a phenomenon that is modeled or found when tuning and modifying car setups in game, for example when you change downforce settings?

 

[Scaff]

I just want to say that I found this thread very helpful, especially Scaff's posts.

I too was under the impression that it was all about brake upgrades, thanks for clearing that up.

No problem at all and glad to help.

I'm a big formula 1 fan and always assumed that the brakes fitted on those cars were very strong -as in would stop you very quickly.
However after reading this thread I no longer know what kind of brakes are used in F1. Do the brakes differ much from the ones used in road cars, in terms of 'strength' or does the only real difference lie in durability and heat-loss?

As per the discussion regarding downforce and the huge amount of grip offered by F1 tyres, the brakes are beasts on F1 cars (the tyres and downforce allow in excess of 4g of deceleration). However a lot of that is once again down to the need to repeatedly and controlably brake for
90 to 120 minutes. Quite a demand on any braking system.

As for what they are made of, well that's carbon composite, which allows very high operating temperatures and is extremely light. Bizarre fact of the day, the carbon rotors used in F1 are effectively 'grown' and can take 5 months to make!!

He's some good info on it...http://www.f1technical.net/articles/2



Regards

Scaff

 

[vett'e]

Hi guys!

I just love this kind of debates! So just to stick my nose in, is this a case to be considered (didn't take too much time to think it through so I might be wrong):

Facts:
- the car is "fast"
- car has wings or is shaped to create "significant" amounts of downforce while going fast
- the stock brakes are able to lock the tires while travelling at low speeds while significant downforce is not created
- when the car travels fast, grip increases due to the effect of downforce -> stock brakes no longer have enough power to lock up the tires

SO, would not stronger brakes stop the car faster in this case? Leave out materials, heat dissipation etc etc...

Just a thought =)

Yeah, it gets almost obnoxious, but again that's because some people fail to understand or be it the acknowledgment of other people's comments regardless of its validity.

Good explanation and rebuttals by the way Scaff!

 

[vett'e]

OK still dont agree. Lets test the theory in revese. We take a large fast car and leave everything standard. We drive it at 100mph and hit the anchors. We find that the cars wheels will lock at 40mph. We drive the same car at 140mph. Amazingly the wheels will still lock at 40Mph. Thats when there is enough force in the brakes to overcome the turning force of the wheels. Ok same car same tyres same suspension. we swap out the brakes for smaller ones. we drive the car at 100mph the same and hit the brakes. less friction will mean that there isnt the force to overcome the turning force of the wheels at 40mph. We do however find that the wheels will still lock up all be it now at 25Mph. So though the wheels still lock up the point of maximum braking (just before they lock) is lowered. The distance the car travels between its 40.1mph point of maximum braking and its 25.1Mph maximum braking has to be added to the stopping distance. In the same way adding larger brakes didnt increase the grip in the tyres adding smaller brakes doesnt decrease the grip in the tyres yet we still have an increase in stopping distance? If this wasnt the case manufactures of cars would be finding ways to put on little motorbike sized brake rotors on our cars to save money on the metal it takes to make brake disks. You cant argue with Physics its the Law.. check Newtons law if you dont believe me.

Let's bring some 'physics' in here

W : Work done
F: Force (F = mass x acceleration)
D: Distance

Forgive my lack of caliper knowledge, but say two sets of brake can exert X and Y (X >Y) amount of force, if a car were to come to a complete standstill within 200m. Then the Work done by the brakes will be calculated by the following;

Work done = Force x Distance (W = F x d)
W = 200x and 200y where X > Y

Now, consider a tire that has the grip coefficient of Z.

Both sets of brakes will lock the tires, and the only way the braking distance will increase or decrease is if the grip coefficient of Z changes, this is because the variables X/Y has no effect in Z.

The only advantage X has over Y, is that it will reach its biting point QUICKER than Y because it can exert more force earlier.

Cheers

Vett'e

 

[vett'e]

I was initially perturbed at the lack of brake (it's brake folks, not break!) upgrades but after driving a lot and gradually upgrading the rest of a given cars' performance I'm now thinking the coders have brake power scalability built-in. I mean, as long as I've upgraded the tyres to suit the engine and chassis performance the brakes always seem to be adequate. Am I wrong?

I totally agree, braking hasn't been an issue of mine and I don't foresee one given the right brake balance. I wouldn't necessarily say stock set up is bad though, its adequate in my opinion.

 

[slowman]

Well, I'm with Scaff here on brakes. As has been stated, if you can lock up your tires then your braking system is not the limiting factor. Simple as that. The reason people install big brake kits is for more efficient heat dissipation and fade reduction due to increased surface area. Ceramic systems increase this efficiency. This is the same reason that the switch to disc systems began more than a half century ago. Discs have a much larger surface area and dissipate heat much, much better than drums do.

Anyway, Scaff, thanks for taking the time to write these guides. I printed these off years ago and my guide is still being used frequently. I have notes and comments scrawled all over them along with a few articles from Grassroots Motorsports.

 

[HolyDiver342]

I thoroughly enjoyed reading this thread, I must give my thanks to Scaff for his diligence and patience he had while providing us with his knowledge, even though so few seemed to appreciate it. Thanks again Scaff, I came in knowing little about the subject and left feeling quite knowledgeable.

 

[BlueShift]

I personally think that to stop a car 30% of it is made with a good repartition of weight of your car with brakes repartition / ride height / springs rates / aero / lsd / dampers and anti-roll bars (anti-roll bars when turning only)...

15% of braking distance is made via gearbox/torque distribution.

Tires makes 40% but all the above prevent them to lock too fast.

The last % is pilot's talent, luck (the road's bumps) or ABS.

Racing brakes won't help to stop your car faster.

I think what racing brakes made in GT4, please correct me if I'm wrong, is better heat dissipation. They could brake the same with a more wide range of temperature.

Example :
- same car, same engine-brake ("frein-moteur" in french), same gearbox - let's say automatic, same speed, same strong brakes, same tires, same fat pilot, same everything but suspension. One with bouncing suspension, one with no suspension at all (go-karts for the win )
- you hit the brakes at the same moment. To my mind, the bouncing car will stop faster, even if your spring rate is so low that the suspension will hit your ride, you still had the spring elongation time more than the no suspension car.

Just because back to front weight transfer will be slower on the bouncing car and the strength the tires have to brakes is lower at the begining of your braking that at the end. On the other car, the faster back to front weight transfer will just impact your tire patch and impulse tires lock (aka hello the wall) : 100% of the car's kinetic energy will have to be stopped at the begining of the braking.

But...

Kinetic energy depends on speed.

Let's say you have 130 kilojoules of kinetic energy (thx to the wikipedia, it's a car of 800kg including passenger travelling at 40 mph or 65 km/h).

Let's say your tires locks at 100 kilojoules.

- Car A with no suspension at all, 100% of this energy, 130kJ will be given to your 100 kJ front tires. Tires locks, can absorbs only let's say 50 kJ because of the slipping, you have 80 extra kJ to dissipate somewhere that doesn't exist. Hence the beautifull bumpmapping wall in your head.
- The bouncing car B will get, let's say 75% of this energy in the front wheels and 25% in your back wheels. Tires don't locks and slow the car dissipating to the road 75% of 130 kJ = 82 kJ for the front tires that dissipate the much.
After that let's say you're at 33mph / 54kmph. The kinetic energy of a car @ 33mph = 54km/h is 90kJ, that the dampers gives 100% in the front wheels at this moment of the braking (for exemple) => no tire lock, no bumpmap for you.
Your suspension slowed the rear-to-front energy transfer slow enough so you can brake efficiently.

The pilot's talent comes in when your brakes are set strong or if you have a hard suspension. You know that after a certain speed you can jump on your brakes but at the beginning you must brake slow. ABS compensate that.

Anyway, if your racing soft/soft gives you 100 kilojoules before they locks, there's a minimal distance a car of 800kg can stop, no need to argue over brakes' sizes guys.

The only solution to avoid this energy transfer is parachutes, like on dragsters or fighter planes. If there was another solution military ingeneers would use it.
Tissue parachutes on rocket-powered planes are not a very safe and easy solution to implement.

(sorry for the engrish wall of text)

 

[Scaff]

Blue-shift. You have made a few inaccurate assumptions in your piece above (if I'm reading it right and I'm not 100% sure of that).

One of the first things is in regard to what cause a tyre to loose grip when braking in a straight line, while 'energy' is a factor in it (of course) its actually measured in the difference between the speed the tyre is rotating and the speed the vehicle is traveling. The difference is know as the slip percentage, as slip percentages increase the grip available increases:

This occurs up to a point, after which the grip drops off and the tyre/wheel will lock.

Now while suspension will have an effect on this, its not in the amount of weight/load transferred, rather in the speed in which it is transferred. Take two identical cars, one of which has had the suspension removed and replaced with steel bars. When the both brake to the same degree, the weight transfer that occurs will be the exact same. What will differ is that the car with steel bras will not been seen to 'dive' under braking and the load transfer will occur much more suddenly.

You are quite right that this can have an effect on how the tyres react and it is possible to overload the tyres with a heavy braking foot and stiff suspension. However you are only partial right to say that "You know that after a certain speed you can jump on your brakes but at the beginning you must brake slow."

You should apply brakes with a firm and smooth action to quickly, but smoothly get the the threshold (to avoid the rapid overload I discussed a moment a go), you need to also ease off the brakes when you begin to slow as maintain the same braking pressure can cause lock-up as well.

This can occur for one of two (related) reasons.

The first is down to slip angles (see above), at lower speeds the differences are smaller (10% slip at 100mph is 10mph, but at 30mph is only 3mph), so it becomes far easier to exceed the slip percentage at lower speeds.

This second is down to downforce, in a car that is producing true downforce you get the benefit of the additional grip that it provides when braking. However downforce only occurs above certain speeds (it varies but from 60mph+ is a good rough figure), as such when you brake hard in a car producing a lot of downforce you get a huge amount of grip available (and massive slip percentages to use). Unfortunately as soon as you drop out of the downforce all that additional grip disappears and you are back to the 'normal' slip percentages for your tyres. As a result drivers (particularly in LMP class cars and F1, etc) find they have to back off the brakes to a very large degree when they drop below a certain speed or risk locking the tyres up to quite a large degree.



Scaff

 

[nomis3613]

Hi Scaff, sorry for being painful but I'd like to raise a point about the dreaded Brake Fade debate.

Most of the testing (both real-life references and GT, ok except this) are based on a single stop. I totally agree that bigger brakes can make no difference in this case. But in real-life circuit racing, if the brakes have not cooled for the next corner, then they won't have enough power to reach the tyres' potential, so the braking distance will suffer. You buy your big rotors with 6 pot calipers to get shorter stopping distances for the 2nd, 3rd, etc stops.

I won't question your judgement that GT5 still doesn't include brake fade (I haven't driven GT5 much yet), so the "Single Stop theorem" can be applied to GT5. But anyway I just wanted to bring this up because the thread is a mix of real-life and GT5 discussion, so I thought the limitations of this theorem (for the real-life references) should be pointed out.

 

[Scaff]

Hi Scaff, sorry for being painful but I'd like to raise a point about the dreaded Brake Fade debate.

Most of the testing (both real-life references and GT, ok except this) are based on a single stop. I totally agree that bigger brakes can make no difference in this case. But in real-life circuit racing, if the brakes have not cooled for the next corner, then they won't have enough power to reach the tyres' potential, so the braking distance will suffer. You buy your big rotors with 6 pot calipers to get shorter stopping distances for the 2nd, 3rd, etc stops.

I won't question your judgement that GT5 still doesn't include brake fade (I haven't driven GT5 much yet), so the "Single Stop theorem" can be applied to GT5. But anyway I just wanted to bring this up because the thread is a mix of real-life and GT5 discussion, so I thought the limitations of this theorem (for the real-life references) should be pointed out.

If you go back and read all that I have written and quoted on this subject (and I am more than aware that's quite a bit), you will find that brake fade has been covered a number of times.

It is of course a reason why you (may) need to fit bigger brakes or better cool your existing brakes or both in the real world.

Its also the reason why (and again this has been covered before) racing brakes were pretty much pointless in GT4 (unless you were running very soft racing tyres) and why the omission of them from GT5 is not a big deal.

Now get GT5 modeling brake fade and I quite agree we will need a good range of brake system upgrades and cooling options.


Regards

Scaff

 

[David_GT]

Scaff is 100% right, in this case bigger pads would be absolutely redundant because as long as you have enough surface area to lock the wheels so the tyre can grip then larger brakes aren't going to lock it any faster. Cooling isn't taken into acount in GT5, I have experience using heavy machinery(tractors, diggers that sort) and on one model of a Deutz Fahr tractor they have a brake system that doesn't use brake cooling fluid(not sure of the technicalities of it sorry) and the tractor has to compensate by having much larger brake pads and it doesn't stop any slower from other tractors I have driven, the best for stopping is air brakes regardless of pad size you're glued to the road, most 50kmh tractors use them.

Oh and on a side note, its good to be on a forum that sticks to proper grammer and sentence structure, I have been so annoyed by some where you see "lyk dis is ur wkd car" fair annoying.

 

[Nvedamuthu]

Hi guys!

I just love this kind of debates! So just to stick my nose in, is this a case to be considered (didn't take too much time to think it through so I might be wrong):

Facts:
- the car is "fast"
- car has wings or is shaped to create "significant" amounts of downforce while going fast
- the stock brakes are able to lock the tires while travelling at low speeds while significant downforce is not created
- when the car travels fast, grip increases due to the effect of downforce -> stock brakes no longer have enough power to lock up the tires

SO, would not stronger brakes stop the car faster in this case? Leave out materials, heat dissipation etc etc...

Just a thought =)

Not sure, but the last time I remember, larger brakes were used to reduce heat and wear, and carbon ceramics increase the longevity too. But I think this ties in with what he said, if your brakes can't lock up your tires at any speed, get bigger ones.

 

[BlueFG2]

If your brakes can lock up your tires (with ABS off) then they have plenty clamping force to stop you. The reason why bigger rotors/calipers and more aggressive pads feel like they make you stop faster is because they are able to lock up your brakes with less effort exerted on the brake pedal. So ignorant joe (no offense) will think, "Wow these brakes make my car stop faster", but in reality you simply have less pedal modulation. Only a little bit of pressure on the brake pedal will cause your wheels to lock up or ABS to engage with bigger rotors/calipers and aggressive pads.

There's certainly nothing wrong with putting bigger more aggressive brakes on your car though. Not only do they look great, but it's the easiest way to adjust the brake bias on a real car. In fact I changed the pads on my old Scion tC because it had a very long brake pedal, and made heel-toe downshifting awkward. So with the new pads it made heel-toe easier for me, but if anybody else drove my car they commented on "powerful" my brakes were, but in reality my brake pedal just had very little modulation.

 

[nttdemented]

This is one pretty funny thread. Scaff, I commend you on your patience my friend!

 

[BlueShift]

Blue-shift. You have made a few inaccurate assumptions in your piece above (if I'm reading it right and I'm not 100% sure of that).

I agree 100% with what you said.

In fact, we say more or less the same thing... I'm inaccurate because I made physic studies (electronics in fact) but not in car mechanics. Also I haven't got the habits you have (slip & co 👍 very interesting stuff), I talk about kinetic energy and mecanic theory.
If I get it rigth, your graph should be something like 0.5mv²/v'² where v is the car's speed and v' the tire's... Or something like that.

And because I talk the engrish good very aren't it ?

BTW, I've got some things/theories to expose to you for a GT5 version of your guide.

 

[GusHaines]

Hi,

Some very interesting stuff!

However. The breaks do not directly stop a moving vehicle any more than the interface between your eyes/brain/foot or the break peddle/piston/fluid/piston/caliper/etc (you see what I mean?)

Brakes stop the wheels not the car. Otherwise you would never skid.. or?

So. Better breaks will stop the wheels faster but its the interface between the car and its environment that will bring it to a stop. In most cases this will be the tyres

Regards,
Gus