GT4 and Brakes

Discussion in 'GT4 Tuning' started by Scaff, Mar 18, 2005.

  1. Scaff

    Scaff Staff Emeritus

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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

    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.
     
    bondy_1625 likes this.
  2. HoWheels

    HoWheels

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    :tup:

    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 :tdown:

    -a
     
  3. antisport.net

    antisport.net (Banned)

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

    Scaff Staff Emeritus

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    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.
     
  5. antisport.net

    antisport.net (Banned)

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    sorry if I offended you not my intention
     
  6. GT Kid

    GT Kid

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    Good post.
     
  7. Scaff

    Scaff Staff Emeritus

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    None taken at all, don't worry. :)
     
  8. j8mie

    j8mie

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    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.
     
  9. Div is back

    Div is back

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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.
     
  10. Scaff

    Scaff Staff Emeritus

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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.
     
  11. Civicbus

    Civicbus

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    377
    ^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
     
  12. dbarrade

    dbarrade

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    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 :)
     
  13. bucket of water

    bucket of water

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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.
     
  14. Frizbe

    Frizbe Premium

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    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/]
     
  15. Crayola

    Crayola

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    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.
     
  16. Frizbe

    Frizbe Premium

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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? :) )
     
  17. Crayola

    Crayola

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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)
     
  18. Scaff

    Scaff Staff Emeritus

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    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.
     
  19. Maven

    Maven

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    261
    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.
     
  20. Scaff

    Scaff Staff Emeritus

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    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
     
  21. MR_GT

    MR_GT

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    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"
     
  22. Scaff

    Scaff Staff Emeritus

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    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.
     
  23. Eric.

    Eric. Premium

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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.
     
  24. Swift

    Swift Staff Emeritus

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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.
     
  25. Scaff

    Scaff Staff Emeritus

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

    Scaff Staff Emeritus

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    Thanks Swift, just trying to help people out.
     
  27. bazzone

    bazzone

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    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?
     
  28. MR_GT

    MR_GT

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    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.
     
  29. Rzeractor

    Rzeractor

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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
     
  30. mustang_4_ever

    mustang_4_ever

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    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 :tup:
    in this case a ruf btr maxed out on rally george paris