GT4 and Brakes

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Due to the sheer size and interest in this thread (and my thanks to all involved) I have edited this first post to become a summary and index to all that has been discussed, tested and debated here.

The original first post I made is quoted below and if this is your first visit here, welcome, and please read all of this post and follow the links first, as you may well find your question answered.

Regards

Scaff

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The reason I have submitted this thread for approval is to counter a large amount of miss-information in a wide range of threads about the braking performance of various cars in the game and how PD have got it wrong.

The following is taken from a white paper published by Stop Tech

“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.”


To put it simply, your brakes (if working correctly) do not dictate how long it will take a car to stop, your tyres do.

The reason people are complaining that cars such as the Zonda, McLaren SLR & Ford GT take so long to stop is quite simply down to the tyres they are fitted with. Sport tyres (GT4) on cars capable of these speeds will take a long time to slow the car down (the SLR does get a helping hand with the air brake).

Stopping distances are principally dictated by the total area of the contact patch offered by your tyres and the tyre compound.

Discs (rotors), pads, size of callipers, etc do not make you stop any quicker, but they do reduce fade, increase feel and endurance, and allow for greater brake modulation.

Without getting to technical, almost any braking system is capable of applying sufficient force to overcome the grip limit of the tyres and therefore lock the wheels.

If this is the case (and it is) how would more braking power stop you sooner? Quite simply it doesn't, it allows you greater control of the brakes.

The reason it is most evident in the cars mentioned above is that they are very, very fast road cars; fitted as standard (in GT4) with Sports tyres. Try fitting the same tyres to a race car of similar performance (in terms of V-max and acceleration), the stopping distance will increase.

The Ford GT is a good example of this; many people have said that the car has been 'ruined' since GT4 Prologue. However in GT4P the car was fitted as standard with race tyres, run it in GT4 with Sport tyres and of course the braking distances will increase.

You can find more information to support the above in the following series on the Physics of Racing, it is very technical, but worth a look.

Physics of Racing


In anticipation of replies to this post; I have not mentioned the weight of any of the cars above, nor discussed it yet in this post. The reason is quite straightforward, the weight of a car does not significantly affect its straight line braking performance.

What can affect a cars straight line braking performance is weight distribution and transfer, as discussed in the StopTech white paper.

This is part of the reason why tyre technology and development is such a major part of all motorsport, how many times have you heard a driver say (particularly in the WRC) that the race/stage performance was poor because of the wrong tyre choice? Its not always any easy excuse, tyre performance is one of the single most important factors in driving; be its on the track or road.

So in summary, if you find that the Ford GT, etc take too long to stop, then you have three choices. Get better tyres, start braking earlier or don't drive them.

As a last point I am more than happy to use this thread to carry on discussing these matters as they relate to GT4, however please do read the material linked as it may well answer any questions you have.

Summary

As the original post above explains the main reason for this thread being written was to dismiss common misconceptions regarding braking, initially in GT4, but this has naturally expanded to cover real world applications.

A fine starting point (and to save reading the entire thread) is Skant's excellent summary of the entire threads main points.
Skant's summary


Why weight is not a significant factor in braking distance and weight transfer is far more important (but neither is as important as your tyres)

This is without a doubt the single most widly discussed subject on this thread and you will find the main debate and points covered between pages 5 and 9. Please be aware that the statement above is true and before you wish to question it, read ALL of the related threads and linked details.


The true benifits of bigger discs and better pads
Again a good discusion was had with regard to this subject, another common misconception that bigger discs and better pads will stop you quicker (not true - as long as your current brakes are up to the job).

This has been well covered in these posts:Post 1 and Post 2


Threshold Braking

A lot of people have asked what this term means, and to save searching, here is a definition.
Threshold Braking


ABS

What is ABS and how does it work, find all you need to know in this excellent little summary.
ABS


Compression Braking

What is Compression (engine) braking, how does it affect a car and why its application on the road and track are very different.
Compression Braking
Colin Chapman on Engine Braking - supplied by Alfaholic


Setting Brake Bias

A quick look at how to set brake bias in GT4

The Brake Balance Controller



GT4 Brake Tests

A number of regulars to this thread have taken the time to conduct a number of very detailed braking tests, some are designed to test GT4 physics vs the real world and some as just to prove a point. All are useful and of great interest, I hope you agree.

FIDO69's First test
Lazydog's First test
Racing Brakes - Test 1
Racing Brakes - Test 2
ABS
Threshold Vs Cadence braking
ABS - Tsukuba Wet
Ford GT 0 - 100 - 0 - The real world vs. GT4
GT4 Vs Autocar 0-100-0 test database
GT4 Compression/Engine braking
How long is an ml in the data logger (and Ford GT 70-0mph test)
AM V8 Vantage - Brake Balance Controller - Settings test
Weight Reduction Vs Tyres - which is better for braking
Pagani Zonda 0 - 100 - 0 - The Real World vs GT4
Racing Brakes - A test with racing tyres
TCS & Braking - any effect?

I hope that we will be able to continue testing the GT4 braking physics and expect to see more tests linked here in the future.


Links

A series of links that you may find useful, while most refer to real world braking systems and physics, a lot does apply directly to GT4.

Braking Systems - In plain english (an excellent starting place)

ABS and Big Brake Kits

The First Step for Improving Vehicle Dynamics: TIRES

Improved Handling with Anti-Sway Bars

Autocar 0 - 100 - 0 test 2002

Autocar 0 - 100 - 0 test 2003

Autocar 0 - 100 - 0 test 2004

Autocar 0 - 100 - 0 test 2005

Autocar 0 - 100 - 0 test 2006

Brembo Brakes FAQ

Autocar 1999 Tyre test

The Physics of Racing

StopTech White Papers - All of them

ART Chassis Tuning Toe, Caster and Camber

Gearing calculations


Recomended Reading

Speed Secrets (Professional Race Driving Techniques) by Ross Bentley - ISBN 0-7603-0518-8

Going Faster (Mastering the art of Race Driving) by The Skip Barber Racing School - ISBN 0-8376-0226-2

The Anatomy of the Car by Jeff Daniels - ISBN 1-8536-1133-6 (This may be out of print)

Race & Rally Car Source Book by Allen Staniforth - ISBN 1-8596-0846-9



In closing I hope that you find this thread useful and enjoyable, and if you do feel compelled to post, please do so, we are a friendly bunch and always keen to help.
 
👍

Upgraded tires was the best performance mod I have made to my car in real life, and it applies to the game too.

Last night I played around a bit buying different kinds of tires for my Toyota 88C-V, because I wanted to find the optimal ballance between quick lap times and pit stops for endurance races. I found that the handling was so completely poor with the Sports tires, that it wasn't even close to being worth running them. In fact, my hottest lap with sports tires was still slower than my slowest lap before pitting with Racing Medium tires.

And yes, the sports tires on the 88C-V do make it brake horribly 👎

-a
 

Scaff

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not any new news to most, but good write up any hoot...

Thanks, and as you say shouldn't be new to most people; but with the release of GT4 a lot of new members have joined GTP and some of the comments regarding braking needed correction.
 
789
Well said that man!

You would not believe the number of people who are misinformed about what makes a car stop faster. Good write up, and thanks for the article, it's some good ammo against misinformation.
 
2,837
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So do you believe brake physics are improved in GT4?

I did a small test of mine, and I notice in my Ford GT, on La Sarte II, after the long straight, when I brake at 100%, I a lot of time overshoot the corner.

When I brake at around 80 - 90 %, I stop right on time.

Note that I brake when the light starts to flash.
 

Scaff

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So do you believe brake physics are improved in GT4?

I did a small test of mine, and I notice in my Ford GT, on La Sarte II, after the long straight, when I brake at 100%, I a lot of time overshoot the corner.

When I brake at around 80 - 90 %, I stop right on time.

Note that I brake when the light starts to flash.

Sounds like you are locking the brakes up, the slightly reduced braking pressure it stopping the tyres exceed their grip limit. Therefore you stop quicker than with 100% braking force.

That and the higher the braking force the greater the weight transfer to the front, which can lower the maximum grip level of the rear tyres and reduce overall braking efficency.

Given all that and my own exerience with Gt4, yes I do believe that the braking physics are much improved in GT4.

I also think it is a major cause of problems for people, one that you have worked out how to get around, and just as you do in the real world when braking from very high speeds its through the use of threshold braking.
 
^yeah totally agree
the brakes are well modelled this time as I found out yesterday that you actually have to adjust the power more precisely now than GT3 where you could kinda use one setting for everything
 
518
Draith
I am unable to perform a handbrake turn in GT4.

In real life I keep to first gear, turn sharp, then apply clutch (to stop the rear wheels being driven) apply the handbrake untill the wheels block and release, then the rear tries to overtake the front and I spin around smoothly releasing the clutch and back onto the accelerator.

Everytime I try in GT4 I understeer and overshoot the corner, I'm not sure if the front wheels are braking as well, or the hand brake is broke?

Any suggestions?

After watching all those videos of the PD guys testing cars on skid pans I want to send them a real life video of a handbrake turn in my car compared to a handbrake turn in the virtual version of my car.

Apart from that so far I love GT4 :)
 
another problem with the game and you use a controller, its alot harder to 50%, 80% or be smooth with the braking application. therefore you would have to use a lower total brake pressure to prevent tire lock up and increasing your braking distance.
 
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another problem with the game and you use a controller, its alot harder to 50%, 80% or be smooth with the braking application. therefore you would have to use a lower total brake pressure to prevent tire lock up and increasing your braking distance.
I can modulate the brakes rather well using the contorller, alot more so than in GT3. also I have to say GT4 has tought me alot about braking
[/story] Last Saturday I was driving on my favorite back roads while it was raining, well I hit the paint and tried to slow down. But the brakes locked up and I headed straight for the curb, at 30 MPH, so that wouldn't have been pretty. well I thought **** I've locked the brakes up (hydroplaning) and I just released the brakes and accelerated out of the corner. Good times, I LOVE GT4'S PHYSICS!![end story/]
 
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Sounds like you are locking the brakes up, the slightly reduced braking pressure it stopping the tyres exceed their grip limit. Therefore you stop quicker than with 100% braking force.

That and the higher the braking force the greater the weight transfer to the front, which can lower the maximum grip level of the rear tyres and reduce overall braking efficency.

Given all that and my own exerience with Gt4, yes I do believe that the braking physics are much improved in GT4.

I also think it is a major cause of problems for people, one that you have worked out how to get around, and just as you do in the real world when braking from very high speeds its through the use of threshold braking.

I did a bit of an experiment on my bike, I have a speedo and my street is a hill which flattens out at the bottomn, the ashphalt is relatively new so braking is smooth, perfect for this test.

I got some spray paint and drew a yellow mark on the ground, this is where I start braking, I used chalk to mark where my front tire stopped and measured after about 6 goes. I used three methods, locking the back brake, slamming both brakes and go up onto one wheel (I leaned back as hard as I could) and finally using both brakes in moderation, making sure the back wheel didnt leave the ground. Since my street is a hill, getting up to 60 km/h wasnt that easy and tiredness wont have effected the results (this is also why I did each method twice, in reverse order the second time.)

Anyway, the results are as follows. Back brake locked: average 17.6m, both brakes 'slammed' averaged 12.8 and moderating the brakes I managed an average of 11.9.

I figure that when i go up on the front wheel only, the grip threshold on the brake pads is exceeded, therefore I cant stop as quickly. I think this would be similar in a car.
 
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I figure that when i go up on the front wheel only, the grip threshold on the brake pads is exceeded, therefore I cant stop as quickly. I think this would be similar in a car.

No when the grip theshhold is exceded the pads will slip, and your front tire will start to rotate. What you just described (the back wheel lifting off) is wheight transfer, which is good for braking as the front brakes usually do MOST of the work, so a little transfer towards the front is a good thing, but lifting the back tire off the ground is too much transfere and both the brake and front tire are working at their maximum thereshold.
I like the test, really good way to put the physics into terms most should be familliar with (who didin't like locking the back brake up as a kid? :) )
 
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No when the grip theshhold is exceded the pads will slip, and your front tire will start to rotate. What you just described (the back wheel lifting off) is wheight transfer, which is good for braking as the front brakes usually do MOST of the work, so a little transfer towards the front is a good thing, but lifting the back tire off the ground is too much transfere and both the brake and front tire are working at their maximum thereshold.
I like the test, really good way to put the physics into terms most should be familliar with (who didin't like locking the back brake up as a kid? :) )
I know that was what I expected to but I stopped quicker when I didnt brake as hard and both tires were on the ground. Also, I thought I said that when I go onto the front wheel it exceeds the grip threshold of the pad. If I didnt thats what I meant, I didnt get the front tire to slide. (Though I can on gravel)
 

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I know that was what I expected to but I stopped quicker when I didnt brake as hard and both tires were on the ground. Also, I thought I said that when I go onto the front wheel it exceeds the grip threshold of the pad. If I didnt thats what I meant, I didnt get the front tire to slide. (Though I can on gravel)

Its an interesting experiment and well done for the hard work.

However (bet you knew that was coming) bikes and cars are very different when it comes to braking.

Firstly the centre of gravity on a bike is much higher than a car, as a result the weight transfer that occurs is much greater . This is why bikes can be very unstable when braking from high speeds.

Secondly, on push-bikes the braking systems tend to be a lot less effective than on a car or motorbike, thats why you can get pad slip. On a car this simply does not occur (unless the braking system is badly set up or faulty). Instead the brakes will push the tyres past their grip limit and this will lock the brakes and cause you to slid rather than brake.
 
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Good post, although I'm not totally convinced. While I agree that the pads and calipers have little reflection on stopping distance, I would think that weight would be more important than you say and contact area would be less important.

I would say that the softness of the tire compound would be the key. If contact area was so important, wouldn't that mean that reducing the tire pressure would shorten braking distance? I'm not sure, but it seems like it should be the other way around. As well, a lower total weight would mean that less energy would be needed to slow the car.

I'm not an expert in car dynamics, but these would seem to be logical deductions.
 

Scaff

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Good post, although I'm not totally convinced. While I agree that the pads and calipers have little reflection on stopping distance, I would think that weight would be more important than you say and contact area would be less important.

I would say that the softness of the tire compound would be the key. If contact area was so important, wouldn't that mean that reducing the tire pressure would shorten braking distance? I'm not sure, but it seems like it should be the other way around. As well, a lower total weight would mean that less energy would be needed to slow the car.

I'm not an expert in car dynamics, but these would seem to be logical deductions.

Very common misconceptions, and its totaly understandable why you would think that.

Have a read through some of physics of racing series to gain more of an insight, and consider these stopping times from 60mph

Range Rover Vogue 2.7 secs
Lotus Elise 3.0 secs
SL500 2.5 secs
Evo VI 2.5 secs
GTR R33 2.9 secs

All figures from Autocar
 
Less weight, more tire contact, better calipers and disks ALL reduce braking distance. Lowering your tire pressure can shorten OR extent the braking distance, because it all depends on what the best pressure is to get the best tire grip.

Softer (more sticky) tire compounds would shorten braking distance for sure.

I think the problem with simulating real braking in a game like GT4 is that there is no "play" in the brake pedal, unlike real cars. With real cars, you would have to brake 100%. The 80% braking in GT4 is not realistic, but maybe that's the best they could do. Also the tire grip (the most important part of braking) is not realistic in GT4, or maybe there just isn't enough tire "feel"
 

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Less weight, more tire contact, better calipers and disks ALL reduce braking distance.

Only more tyre contact reduces braking distance, the other DO NOT.

Please re-read my first post and the linked sites.

Wieght distribution and transfer do effect stopping distances, overall weight does not (but it is a factor in the weight transfer).

More tyre contact does, as you say (and as does my first post) help with braking distances.

Better calipers and disks have no effect on braking distance in any way, read the linked articles.

I did in my first post ask people to read the linked articles before posting, your statments on the whole are the type of misconseptions that prompted me to write this in the first place.
 

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Only more tyre contact reduces braking distance, the other DO NOT.

Doesn't adding some weight to the front of a car help to a certain extent? That's what I did with my Saleen, and it helped some.
 

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Scaff, excellent job. I think that should be a sticky or at least a link in a sticky. It's just well written and very easy to read and understand.
 

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Doesn't adding some weight to the front of a car help to a certain extent? That's what I did with my Saleen, and it helped some.

Thats the change in distribution of weight that is helping, not the overall change in weight.
 

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Scaff, excellent job. I think that should be a sticky or at least a link in a sticky. It's just well written and very easy to read and understand.

Thanks Swift, just trying to help people out.
 
yur theory on tire wear works out...except about brakes. Your saying that old brakes that struggle to stop the wheel wouldn't effect braking time?
"Better calipers and disks have no effect on braking distance in any way, read the linked articles."
I might be dumb for saying this, but if you can't stop the wheel, what is the point of badass tires?
 
Only more tyre contact reduces braking distance, the other DO NOT.

Please re-read my first post and the linked sites.

Wieght distribution and transfer do effect stopping distances, overall weight does not.

More tyre contact does, as you say (and as does my first post) help with braking distances.

Better calipers and disks have no effect on braking distance in any way, read the linked articles.

I did in my first post ask people to read the linked articles before posting, your statments on the whole are the type of misconseptions that prompted me to write this in the first place

Yes, I read your links...the problem is that saying that the contact patch is the only variable that affects braking distance is simply not true.

Yes, the tire grip is the single most important factor (because the tire is only part contacting the road) but other things can influence the total grip available for the tires. A heavier car will put more "load" on the tires creating less grip, and a lighter car will put less "load" on the tires making more grip available which transfers to shorter braking distance.

I agree with you that "theoretically" pads and calipers don't change the braking distance. Any brake pad and caliper setup these days can make the tires lock, but this is theoretical. Better brake setups are designed so that you can get to 100% braking potential more quickly or easier as well as reducing fade.
 
172
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yer haha the tyres do depend on it
i didnt realise it at first until i wondered why my Z06 wasnt slowing down as quick as I would of liked it...
then i realised it had sports tyres on argh
 
all about enurchia (sp lol) heavy car+high speeds=long breaking
its pretty wierd when u hear the s3's slammed on the breaks, theres not alot of sound, then with r1-5's u can hear the cars tires despretly find tration, quite a sound (in gt4lol) great thread, it only makes me a better driver 👍
in this case a ruf btr maxed out on rally george paris