GT4 and Brakes

  • Thread starter Scaff
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This is getting away from brakes a little and more about the physics (IMO) but a great example is the Viper. At least in GT3 the rear end swung out a lot more often in certain situations because it's naturally more of an oversteer car but no matter how hard I try in GT4 the back will not come around. Now in braking terms to force the car to oversteer I've tried drifting moves and what not and nothing works. I just don't see how the physics are "improved" in GT4. BTW, I never used the aids and usually use med or soft racing tires because of grip in starting off. Even then I'm still spinning tires more than going forward for awhile.
 
VIPFREAK
. I just don't see how the physics are "improved" in GT4. BTW, I never used the aids and usually use med or soft racing tires because of grip in starting off. Even then I'm still spinning tires more than going forward for awhile.
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Thats part of the problem right away, the racing tyres offer levels of grip way above that which you would expect.

In terms of real world comparisons, both for braking, lap times and lateral G cornering N2 or N3 tyres offer the closest match. You do need very good throttle control, but then again if you dialed in max revs in first and dumped the clutch in a real Viper you would be kissing your tyres goodbye in real life.

Have a look at this, as it covers what I mentioned above but in a lot more detail

BMW M3 - An analysis of tyres choice

Regards

Scaff
 
Even though technical stuff makes me snooze real quick I understand what you were getting at. I've always used the selection of tires as my own scale rather than what GT says they are. I go by feel vs realistic and how a car should act. with that said a harder or street tire will give more acurate handling characteristics but at a price of speed (imo). As for breaking I've never got that down, I just go by if the brakes seem to stop too fast or too slow. Thanks for the help though.

BTW, is there any setting suspension wise or other that I can change to make the car oversteer easier so it will be more realistic?
 
Scaff
I would generally not use the BBC as a first line in reducing understeer, we have more than enough suspension tuning to dial in or out understeer. I would recomend setting the BBC to optomise braking stability.
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I prefer not to use toe and camber. Especially toe which can be different when using different controller (digital vs analog = sudden steering vs steady steering). Because on digital the inside tire have more effect on turning than outside tire, On analog the outside tire have more effect on turning than inside tire.
And I think spring rate and ride height (weight transfer) will only affect only one of acceleration or braking, not both if being used equally. And it seems GT physics averaging front and rear setting to simulate weight transfer.
ie. 2/20 spring rate maybe has the same weight transfer as 20/2 or 11/11.
I don't experiment about spring rate and ride height front/rear balance effect on handling though. From what I read high spring rate will provide more grip on the tire, maybe low ride height too.
So, I think the tuning rank to make the car oversteer in acceleration only is (from less to more):
spring rate : 2/2 < 2/20 < 20/2 < 20/20
ride height : max/max < max/min < min/max < min/min
This rank will be reverse if we want to make the car oversteer in braking .

VIPFREAK
BTW, is there any setting suspension wise or other that I can change to make the car oversteer easier so it will be more realistic?
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Try 20.0/20.0 spring rate and min/min ride height, and use 1/1 1/1 damper as starting point. Use toe or camber only when necessary.
 
@VIPFREAK

You will need to be careful with the info that sucahyo has provided as it is based on (I believe) GT2, with teh GT4 physics engine being very different you will find that it may have some unexpected results.

In regard to dialing in oversteer with suspension setting try stiffening up the rear or softening the front spring rate. Adding a little rear toe can have the same effect as well.

Be careful with Toe and Camber settings as they can have a major effect in GT4.

As a general rule of thumb, softening suspension will increase grip at that end and stiffer setting will reduce grip at that end. However be wary of extreme values as these can have the opposite effect.

Spring rate and ride height will effect both acceleration and braking, but rememeber that spring rate does not change the ammount of weight being transfered, just how much the car moves in response to the weight transfer (and dampers control how quickly that movement occurs).

Ride height does change weight transfer as you raise or lower the cars centre of gravity. These effects can be seen in both acceleration and braking.

For more tuning info have a look at the stickied guides at the top of these threads (Ducks Ford GT set-up is a great one for drifting) and the BESTuners thread as well (link in my sig).

In my opinion, if a car is fitted with N2 tyres it does oversteer well, as long as you don't try entering a corner to quickly. Get a BMW M3 CSL and fit some N2 tyres, you should have no problem getting sideways in the car. The picture below is of a stock M3 CSL with N2s, nothing wrong with this oversteer.





@sucahyo - please don't take any of the above as critisism, its just that GT2 and GT4 are very differnt with regard to tuning and set-up.

Regards

Scaff
 
It's all good doods, you guys are re-affirming what I already knew or felt about the setting and the game... I'm just technically challenged. :dunce:

One thing... On the toe when it say's "-" and "+" which one means out and which one means in because in GT that's never seemed clear to me.
 
VIPFREAK
It's all good doods, you guys are re-affirming what I already knew or felt about the setting and the game... I'm just technically challenged. :dunce:

One thing... On the toe when it say's "-" and "+" which one means out and which one means in because in GT that's never seemed clear to me.
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No problem at all, just glad to be of help.

With regard to Toe settings the official guide states that Toe-out is + and Toe-in is -, same for both front and rear. This is the convention I follow and have found it to work.

Good luck.

Regards

Scaff
 
Scaff
@sucahyo - please don't take any of the above as critisism, its just that GT2 and GT4 are very differnt with regard to tuning and set-up.

Regards

Scaff
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Ok,
.Duck. has kindly doing test on my request about spring rate and damper (I still waiting his permission to post it in here), and my impression is using very hard spring will give more sharper handling on F1, but to neutralize handling we need both spring and damper. Using medium spring and very high damper will make sluggish handling but stable.
.Duck. usually use lower front ride height to get better cornering and straight line stability.
 
Scaff
With regard to Toe settings the official guide states that Toe-out is + and Toe-in is -, same for both front and rear. This is the convention I follow and have found it to work.
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It's the complete opposite for me. Take for example the Ginetta G4. When I tuned it a few months ago, I had a problem with stability after the rise at Midfield. And then I noticed that the toe was -1. So I set it to 1 and it was much more stable. And the toe numbers were in the rear.

With other cars I've tuned, I tried out using 0 toe (in the rear), and it understeered. Set it to -1, and it had near perfect, neutral handling. Set it to 1, and it understeered to the point of no return.

I don't know which guide you have, but if it's the Prima one, don't trust a word that comes from it. It's one of the dumbest guides I've ever laid my eyes on.

Duck
 
sucahyo
Ok,
.Duck. has kindly doing test on my request about spring rate and damper (I still waiting his permission to post it in here), and my impression is using very hard spring will give more sharper handling on F1, but to neutralize handling we need both spring and damper. Using medium spring and very high damper will make sluggish handling but stable.
.Duck. usually use lower front ride height to get better cornering and straight line stability.
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I think someone other than me has to try out what I did. I'm no "scientific test" person, so don't take this as fact.

And here's my test that I did:
Me in a PM with sucahyo
This is with the F1 car @ Nurburgring.

1. With the springs at 20 / 20 and both bound and rebound at 10 / 10, the car was very unstable, very unpredictable.

2. With the springs at 20 / 20 and the bound/rebound at 1 / 1 each, the car was more stable, but understeered slightly more.

3. With the springs at 10 / 10 and the bound/rebound at 10 / 10 each, the car handled better than #2 and was a bit more stable than #2. But it was more sluggish than either #1, #2, or #4.

4. With the springs at 17 / 17 and the bound at 3 / 3, and rebound at 6 / 6, the car was slightly less stable than #3, but had sharper handling.


I tune using #4, and even though for bumpy tracks #3 was better, the majority of tracks in GT4 are relatively flat, so #4 would be better for an overall tuning.

Also, the scrolling bar in GT4 says about dampers that the higher the numbers are, the quicker the wheel will bound and rebound.

Duck
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Duck
 
.Duck.
It's the complete opposite for me. Take for example the Ginetta G4. When I tuned it a few months ago, I had a problem with stability after the rise at Midfield. And then I noticed that the toe was -1. So I set it to 1 and it was much more stable. And the toe numbers were in the rear.

With other cars I've tuned, I tried out using 0 toe (in the rear), and it understeered. Set it to -1, and it had near perfect, neutral handling. Set it to 1, and it understeered to the point of no return.

I don't know which guide you have, but if it's the Prima one, don't trust a word that comes from it. It's one of the dumbest guides I've ever laid my eyes on.

Duck
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The guide is the official Piggyback one.

Negative toe at the rear (in a rear wheel drive car) is going to cause instability at speed. The tyres are pointing in which will result in reduced lift off oversteer.

A small amount of positive toe (at the rear again) will help stability but make the car more prone to lift-off oversteer, which from the way you set cars up seems to suit your driving style.

Toe also has to be set with consideration to the other settings, particularly camber.

Have a look at the following - Chassis Tuning

It may be real world based but it is useful.

Personally I rarely use rear toe setting (apart from FWD cars), but do use a bit of front toe (around 1 - 2) to aid in initial turn in.

Regards

Scaff
 
Scaff
The guide is the official Piggyback one.
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Lets hope that book is correct, because in GT2 + is toe in. I think we should wait until someone can show the result of using +6.35 toe in GT4.

Scaff
Negative toe at the rear (in a rear wheel drive car) is going to cause instability at speed. The tyres are pointing in which will result in reduced lift off oversteer.

A small amount of positive toe (at the rear again) will help stability but make the car more prone to lift-off oversteer, which from the way you set cars up seems to suit your driving style.

Toe also has to be set with consideration to the other settings, particularly camber.

Have a look at the following - Chassis Tuning
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in GT2, using front toe will help on low speed cornering, but make the car turn harder on high speed.
Using -6.35 for front toe will make the car turn harder on 70kmph, and will not turn at all at 150kmph. Using +6.30 for front toe will make the car turn easier on 70kmph but will not turn at all at 200kmph.
Using -6.35 for rear toe will make the car tail happy, the car will easily tail slide (at 70kmph) with the slightest touch of turn button on straight. Using +6.30 for rear toe will make the car turn happy, it will turn it self (at 70kmph) on the slightest bank.

My favorite quote for toe is
eforer
Just to clarify the whole reaction to toe-in/out in regards to vehicle dynamics. I am a casual GT player, but an avid real (no condesention implied) car and radio controlled car racer. When getting in to chassis setup stuff, I knew that toe in increased stability and toe out decreased stablility (increased reactivity and oversteer) through experience and everyone in the community telling me so. It didn't make sense to me though, I thought the oppisite would be true based on the reasoning cango_uk posted a page previous. What I didn't understand was the importantance of mechanical weight transfer resulting from a combination of steering angle of inclination, caster and scrub radius.

Caster and SIA have the effect of raising the outside tire in a corner and lowering the inside tire when you turn the wheels, ie the ride hieght at the outside front of the car is lower and higher at the inside front. This effectively weight jacks the car the wrong way, loading the inside front tire for inital turn in until the vectored forces of direction change cause the weight to transfer to the outside tires on the corner.

The long and short of this is that your initial turn in (before the car transfers weight due to direction change) is largely controlled by the inside tire, not the outside. Thus, toe-out actually sets the tire that does the most initial steering (the inside) with a more radical steering angle than toe in would. As the car transfers weight to the outside wheels, the effect is neutralized as the outside tires are actually less turned in (partially due to ackerman as well). Toe out makes vehicles more sensitive to inital steering, giving them more cut and making them more reactive to direction change. Toe in does the oppisite.

In karting and 1/12th scale rc racing where there is little suspension travel this effect is used to a ridiculous extreme with incredible caster angles used to violently setup the inside tire (usually toe'd out a bit) to cut for a lot of inital steering.

I still have no idea what + or - toe means in gt though!
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sucahyo
in GT2, using front toe will help on low speed cornering, but make the car turn harder on high speed.
Using -6.35 for front toe will make the car turn harder on 70kmph, and will not turn at all at 150kmph. Using +6.30 for front toe will make the car turn easier on 70kmph but will not turn at all at 200kmph.
Using -6.35 for rear toe will make the car tail happy, the car will easily tail slide (at 70kmph) with the slightest touch of turn button on straight. Using +6.30 for rear toe will make the car turn happy, it will turn it self (at 70kmph) on the slightest bank.
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OK first off how Toe in and out effects handling in the real world.

Front Toe-in = Increased stability at speed (less likely to wander) with average turn-in.

Front Toe-out = Better initial turn-in, car less stable at speed and can wander.

Rear Toe-in = Reduces the effects of lift off oversteer

Rear Toe-out = Increases the effect of lift off oversteer and in rear wheel drive cars the effect of power-on oversteer.


As has been said in the piece you quoted, front toe is effective when initially turning into the corner, with the effect ending as the weight transfers from the inside front to the outside front tyre.

Rear toe is effective when the throttle is lifted mid-corner or on exit in rear wheel drive cars. Increased rear toe is very effective in front wheel drive cars, but can cause instability in rear wheel drive cars (increased oversteer).


Given the example above that the car in GT2 is easier to turn-in at 70kmh with a front toe setting of +6.3 and harder to turn-in with a front toe setting of -6.3, whould tend to indicate that + is toe out and - is turn in! From your info the toe-out setting (+6.3) is also allowing you to reach a higher speed before the turn becomes impossiable.

sucahyo
Lets hope that book is correct, because in GT2 + is toe in. I think we should wait until someone can show the result of using +6.35 toe in GT4.
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See above, which is very wierd because it does not represent your linked test???

The only thing I can say is that its been quite a while since I've played with tuning on GT2.


Regards

Scaff
 
Scaff
Given the example above that the car in GT2 is easier to turn-in at 70kmh with a front toe setting of +6.3 and harder to turn-in with a front toe setting of -6.3, whould tend to indicate that + is toe out and - is turn in! From your info the toe-out setting (+6.3) is also allowing you to reach a higher speed before the turn becomes impossiable.
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Visually, + looks / \.
By using +6.35 toe, we can see how the wheel aligned more clearly,
RUF +6.35/0.00 toe


R34 +6.35/0.00 toe (255/128 memory editor)


even from bird view.
Red = -6.35
Blue = +6.30


I think the initial turn only happens for a very short time, because the car turn very very slow compared to neutral toe. So this will make the outside tire have more effect on turning. With this, the equation reverse, + is toe in, - is toe out.
My first test confirm this, but I have problem to show it with only picture. I think I will redo my test in different way to show the difference better, maybe with not so extreme value :).
I post the test at my side by side thread
 
sucahyo
Visually, + looks / \.
By using +6.35 toe, we can see how the wheel aligned more clearly,
RUF +6.35/0.00 toe


R34 +6.35/0.00 toe (255/128 memory editor)


even from bird view.
Red = -6.35
Blue = +6.30


I think the initial turn only happens for a very short time, because the car turn very very slow compared to neutral toe. So this will make the outside tire have more effect on turning. With this, the equation reverse, + is toe in, - is toe out.
My first test confirm this, but I have problem to show it with only picture. I think I will redo my test in different way to show the difference better, maybe with not so extreme value :).
I post the test at my side by side thread
Click to expand...


I don't have a problem with your pictures, its just very strange that the description of how you say the car handles seems to reflect conventional thinking (toe out + = easier turn in), but the way the wheel seems to face visually is different.

However this is all for GT2 and you are right that the use of such high value could be causing the issue here.

I'm going to try and spend more time looking at this one, as the 'Official guide' clearly states that - values are toe in and + values are toe out, my own experience with how the cars behave on turn-in (for front toe) would seem to back this up.

Toe however is very sensitive to other settings and the limited range (and dumbed down effect) in GT4 make it difficult to be 100% sure.


Regards

Scaff
 
sucahyo
TCSC has effect on braking on GT2, in fact the greatest effect is on braking not accelerating. I do the test with normal & hybrid TCSC value.
Do this also happen in GT4?
This is the GT2 desc for TCSC
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From memory the GT4 description of TCS is the same (I'm at work at the moment so I can't confirm 100%), and while I have played around with it before I have not carried out any detailed tests.

I have tested ASM (which directly mentions braking in its description - unlike TCS which only mentions backing off the throttle) and the results were very small. So small that they could easily be put down to a margin of error.

I may have some time tonight to run so tests on TCS in GT4, I will use the same test set-up as in the ASM tests so they can then be compaired side by side.

Regards

Scaff
 
TCS & Braking

At sucahyo's request I have carried out some braking test with and without Traction Control, to see if it has any effect on stopping distances.

The tests will be run in the same way as the earlier tests on ASM; so TCS will be set at o and 10, with Brake Bias set to 3/3 and 24/24. this allows us to see the effect of TCS with varying levels of brake force.

The car used will be a stock Ford GT running on N2 tyres nad braking from 200mph to 0mph, the average stopping distance of six runs will be taken.

The Tests

TCS 0
BBC 3/3

Stopping Distance = 340.2m


TCS 10
BBC 3/3

Stopping Distance = 340.1m


TCS 0
BBC 24/24

Stopping Distance = 346.55m


TCS 10
BBC 24/24

Stopping Distance = 346.55m


Conclusion
Well its quite clear to see that the TCS setting in GT4 has no effect on stopping distances at all, of note is the fact that the TCS light (when TCS was set) did not flash at all under braking.

I have to say that the results do not surprise me at all, as the description of TCs operation in the GT4 set-up screen describes how it will back off the throttle if it senses traction loss. As the throttle is not in use under braking (big surprise that - doh) even if the TCS did try and back off, not throttle input is present to back off from; however as the light did not activate once under braking I get the feeling it did not even try.

What the tests above do show, yet again, is the problem that can be encountered if Brake Force is set too high. The GT's stopping distance is over 6 meters longer with Brake Bias set to 24/24, over a cars length, a very big difference indeed. This again highlights the need for good Brake Bias settings, as the ability to optimise stopping distances makes a big difference.

Regards

Scaff
 
I don't know if everyone but me has figured out that the brake controller is worthless but it is too me. I don't use it but if I'm forced to I keep it on 1. Since then the cars seem to brake more realistically to me and some of the handling like excessive understeer has gone away. The Viper still doesn't handle like it should but it's more enjoyable now.
 
VIPFREAK
I don't know if everyone but me has figured out that the brake controller is worthless but it is too me. I don't use it but if I'm forced to I keep it on 1. Since then the cars seem to brake more realistically to me and some of the handling like excessive understeer has gone away. The Viper still doesn't handle like it should but it's more enjoyable now.
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I personaly find the brake balance controller to be a very handy tool, one I use a lot of the time.

In terms of casr braking realistically, if you are talking about stopping distances and times then tyres are a much, much more impportant factor. With N2 and N3 tyres being the closest match, as tested with a range of cars againsts Autocars 0-100-0 test results.

However if its braking feel that you find unrealistic, well thats a much more personal area. I like a fairly low setting myself, as I find higher settings can be a little quick applying full braking force, generally in the region 4 - 6.

I've also tested the BBC and its effect on stopping distances, and while you can't improve your stopping distance beyond the tyres limit, you certainly can ensure you maximise it. Get the setting wrong and it does increase you stopping distance.

If you are interested the tests I mention above (and a lot more tests and other stuff) are all linked to from the first post in this thread. If you do have a look around I hope you find it informative and useful.

Regards

Scaff
 
Cool, thanks. Unfortunately, wouldn't use it all that much because I go on what it should feel like to me since I associate it so much with reality. I guess that's why I like GT3's handling better.
 
VIPFREAK
Cool, thanks. Unfortunately, wouldn't use it all that much because I go on what it should feel like to me since I associate it so much with reality. I guess that's why I like GT3's handling better.
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Do anyone in GT3 verify what the value of brake controller when it is not fitted?
In GT2 when not fitted with brake controller the BBC value is 12/12 (gamesharking)
In GT4 it should be different on every car, as the default setting is different for every car (according to Scaff that is :) ).

So, if stock car GT3 has brake performance close to real life, in my opinion, changing the value to minimum will make it less close to real life.
 
sucahyo
Do anyone in GT3 verify what the value of brake controller when it is not fitted?
In GT2 when not fitted with brake controller the BBC value is 12/12 (gamesharking)
In GT4 it should be different on every car, as the default setting is different for every car (according to Scaff that is :) ).

So, if stock car GT3 has brake performance close to real life, in my opinion, changing the value to minimum will make it less close to real life.
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Sucahyo, sorry I can't remember ever saying that every car has a default BBC setting in GT4, ever car I've tested has a default set-up of 3/3 when you first instal the BBC.

What I have said is that the correct BBC setting for each car is different, and will change even in the same car as you change the set up or modify certain areas of the car.

Regards

Scaff
 
Scaff
Sucahyo, sorry I can't remember ever saying that every car has a default BBC setting in GT4, ever car I've tested has a default set-up of 3/3 when you first instal the BBC.

What I have said is that the correct BBC setting for each car is different, and will change even in the same car as you change the set up or modify certain areas of the car.
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Oh, I see, my mistakes .............
 
In away, the 3/3 setting IS individual, since it will not effect car A the same way as car B...somewhat farfetched, but true in a sence.
 

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