GT4 and Brakes

[Swift]

Setting Brake Bias

What the Brake Balance controller is not for.

With a few exceptions I would never recomend using the brake balance controller to trim understeer or oversteer (despite what the GT4 screens say). Use of the brake balance controller to do this can and does have a serious effect on braking distances.

You have plenty of other tools to manage under and over steer in the spring rates, ride height, damper and roll-bar settings. These give you more then enough to do what you need, leave the brake balance to maximise your braking performance and ensure stability under braking.

The only exception to this would be in setting a car up to drift, here outright lap-times are rarely an issue and a high rear bias will cause the rears to lock first making it easier to initiate a drift. Once again, however, car needs to be taken with the settings.

Hope that the above helps.

Regards

Scaff

This is probably the best part of the write up here. Very well done, AGAIN , Scaff. Thanks.

 

[Scaff]

Thats quite....difficult... I'm jealous that you know this much about tuning
It's so complicated, I think I have to read it again tomorow to really let it sink in...💡 It's very fun to read though:tup:

But I still see it as an offence to.....

Its not as complicated as it sounds, just take each part one step at a time; I will try and put together a more practical example tonight if I get the chance.

This is probably the best part of the write up here. Very well done, AGAIN , Scaff. Thanks.

Thanks, swift. The piece you quoted is a major thing for me, we have a huge range of settings that let us adjust the handling characteristics of the car and only one for the brakes, yet still the Brake Balance controller gets used to adjust the handling for circuit set-ups.


I just can't believe that the GT4 & Brakes thread has been here this long I never thought "maybe it would be useful to explain how to actual set the brake balance controller"!!!


Kicks self in the backside and thanks G-T-4-Fan for getting me to do it.

Regards

Scaff

 

[Greycap]

One thing just popped into my mind: isn't it easier to overload the front tires, as they already hold a lot of weight, by increasing the front braking force?

OK, maybe i'm just dumb.

 

[Scaff]

One thing just popped into my mind: isn't it easier to overload the front tires, as they already hold a lot of weight, by increasing the front braking force?

OK, maybe i'm just dumb.

As with weight transfer in cornering the tyres (in this case normally front and rear) will be able to brake upto the maximum grip avaliable to them.

Tyres with a greater download (normally front) will be able to provide more grip and do more of the braking effort, hence the reason why the braking force can be increased to them. The tyres with the lower download (normally rear) will have less grip availiable to them and be able to provide less of the total braking effort.

You are however quite right that a limit does apply to the amount of work a tyre can do, in braking (and acceleration) its governed by the slip percentage, which is the difference between the speed at which the tyre is rotating and the speed of the vehicle itself. Exceed the slip angle and the tyre will lose grip and the wheel will lock.

In GT4 this could be caused by setting the brake force too high, remember I am talking about both the ratio between the front and rear settings (which is the bias) and the actual values set (which is the brake force itself).

So why not just increase the values until you get a ratio that is right? For example Car A could run with a brake balance of 9 / 3, which would give 75% : 25%, however this may or may not work, depending on the tyres and the driver.

As has been discussed before the brake balance controller (unlike in GT3) does not just control the ratio, but also the level of force applied. Set it too high and the ABS will kick in and you will end up increasing you braking distances. You may be able to control this through good brake modulation (use the brake force indicator in the HUD as a guide).

Once again trail and error is one of the best ways of determining what the setting should be, for example our car B may have the following setting dependent on tyre.

N's = 6 / 1 (85.7% : 14.3%)

S's = 11 / 2 (84.6% : 15.4%)

R's = 17 / 3 (85% : 15%)

So in the example I looked at earlier (shown above) if you used the 17 / 3 setting with N2's you would run the risk of locking the tyres much more quickly.

If GT4 modeled brake/tyre lock-up more accurately (the ABS kicks in almost all the time) then it would be much more important that it currently is.

In any case, whatever the values, brake/tyre lock-up is to be avoided at all costs, but if it does happen its far better for the fronts to lock that the rears. As fronts locking first is far more controlable than rears.

Hope that makes sense.

Regards

Scaff

 

[G-T-4-Fan]

Wonderfull. This is a thread that REALLY deserved it's sticky:tup:
I think this thread+ MSpecs sticky are the only things you need to fully understand all the settings in GT4.

I thought I understood them since a long time, because of drifting. Because if I know how to create massive oversteer it isn't that hard to just make a acar handle balanced right? Ok I was VERY wrong. This is more difficult than drift settings.

Overall, braking and the toe settings impressed me the most in GT4. I never quite understood toe, because the left and right wheel are always counter productive to eachother. But the now I found out the WEIGHT is the key factor:tup:

Thats going offtopic, I'll shut up now and just say thanks
THANKS!

 

[~Sp33~]

w00t, look at scaff go ~ like a racehorse~!!!

Great write up, its very helpful with little things in the game, especially brake settings ( even more especially the brake-balance controller) are very hard to understand, the game doesnt exactly explain how it is adjusted (although lucky for me i knew what it was for). Thanks for the insight,

~Sp33~

 

[Scaff]

w00t, look at scaff go ~ like a racehorse~!!!

Great write up, its very helpful with little things in the game, especially brake settings ( even more especially the brake-balance controller) are very hard to understand, the game doesnt exactly explain how it is adjusted (although lucky for me i knew what it was for). Thanks for the insight,

~Sp33~

No problem at all, just glad it is of interest and use.

Ta

Scaff

 

[jamaican]

i did duck's settings with the ford GT '05... and whenever i'm coming into a corner as soon as i touch the brake the rear comes flying around... even if i slightly touch the brake. what's causing this? the brake settings or is it because i'm gearing down and the compression locks up the wheels? or maybe even that decceleration setting... i dunno

 

[Scaff]

i did duck's settings with the ford GT '05... and whenever i'm coming into a corner as soon as i touch the brake the rear comes flying around... even if i slightly touch the brake. what's causing this? the brake settings or is it because i'm gearing down and the compression locks up the wheels? or maybe even that decceleration setting... i dunno

I will have a look at Ducks settings and let you know what I find.

Regards

Scaff

 

[jamaican]

i kinda exaggerated on the "even if i slightly touch the brake" but still, the tail comes flying around when braking.

like i was goin about 200 mph on the long straight of the nurburgring and the car was bouncing, but that's ok i kinda expected that because of the stiff suspension set-up; at the end of the straight when braking up for the corner it's like the ford gt is only made for braking in a straight line; the slightest steer one way, and the car goes the other way

PS... could it be all the weight in the rear... with the engine and everything?

 

[Scaff]

i kinda exaggerated on the "even if i slightly touch the brake" but still, the tail comes flying around when braking.

like i was goin about 200 mph on the long straight of the nurburgring and the car was bouncing, but that's ok i kinda expected that because of the stiff suspension set-up; at the end of the straight when braking up for the corner it's like the ford gt is only made for braking in a straight line; the slightest steer one way, and the car goes the other way

PS... could it be all the weight in the rear... with the engine and everything?

Ok I've had a bit of time to run the settings you mentioned, with a similar set-up in terms of modifications. I had to run them at Midfield (Duck's settings use this track for a benchmark time) due to a lack of time, so they may still need tweaking for the 'ring.

Now you should always remember that settings rae a very personal thing as they are developed for that drivers style.

Duck's setting I found give the Gt a very tail happy attitude, more than I personally like, also the high rear ride height (in relation to the front) and equal brake bias will lead the car to a tendancy to oversteer on the brakes when turning. Again this is not to my personal tastes (nor by the sound of it yours.

While I am sure that Duck's settings suit his driving style, I needed to start from scratch, as my best time with the settings was 1.19:210.

I first ran the car with all the settings at default and to my surprise dropped to a time of 1.17:404!

I then tweaked and tested until I had the following (all F/R)

Spring Rate 10.5 / 13
Ride Height 98/98 (default)
Bound 4 / 5
Rebound 6 / 7
Camber 2.0 / 1.0 (default)
Toe -1 / 0
Roll bars 4 / 5

Brake Bias 5 / 3

All other settings were left default, you should also be aware that I never fitted the wing, as I generally prefer the car without one.

The end result was a lap of 1.16:020,which I was quite happy with given the hour it took me to get these.

Give them a go and let me know what you find, if I has time tomorrow I will try with the wing and at the 'ring.

@Duck - if you do read this, please do not take the above as a cheap shot at your settings. I am a firm believer that settings need to match the drivers style. My settings above may well feel totally wrong to yourself, but they work for me.

Regards

Scaff

 

[dudejo]

btw, the Ford GT is a midship engined car.

that kind of car usually turns more when you lift off the throttle so that might explain why the car oversteers when braking.

 

[Scaff]

btw, the Ford GT is a midship engined car.

that kind of car usually turns more when you lift off the throttle so that might explain why the car oversteers when braking.

Very true, even with my settings as its a mid engined car trying to turn while hard on the brakes is going to be a problem. It will now however handle trail braking into a corner a lot better for me.

Regards

Scaff

 

[DuckRacer]

@Duck - if you do read this, please do not take the above as a cheap shot at your settings. I am a firm believer that settings need to match the drivers style. My settings above may well feel totally wrong to yourself, but they work for me.

It isn't a cheap shot. The best settings for each individual are their own. 👍

Needless to say, I'll probably need to retune the GT. Thanks for bringing up this issue.

Duck

 

[Scaff]

It isn't a cheap shot. The best settings for each individual are their own. 👍

Needless to say, I'll probably need to retune the GT. Thanks for bringing up this issue.

Duck

Thanks for being cool about it Duck, some may have got all protective.

One thing I forgot to mention above, while your settings did not allow me to obtain the fastest possiable laptime out of the car, they are damn fine for getting the back of the car out in a controlable manner.

So a big 👍 for that.

Regards

Scaff

 

[jamaican]

yea thanks for being cool about it duck... your settings are wicked, i liked the 190e settings you gave me but the gt ford settings didn't suit my kind of driving

 

[sucahyo]

It seems that nobody test the effect of using different Brake ballance number on GT4 yet.

This is the test that I do in GT2, maybe someone willing to test it on GT4? I just want to find out if the brake is the same on GT4. I note the braking time and then calculate the distance.I get the time by play the braking video record very slowly (per frame).
This is all using 100% braking.

250 to 50 braking test (kmph),
front/rear = time (second) = calculated braking distance (meter)
jaguar xjr :
12/12 = 3.676 = 205
01/01 = 3.224 = 180
24/24 = 3.635 = 203
01/24 = 3.241 = 181
24/01 = 3.717 = 208
no controller = 3.470 = 194

spoon integra:
12/12 = 3.899 = 218
01/01 = 3.758 = 210
24/24 = 3.593 = 201
01/24 = 3.593 = 201
24/01 = 3.758 = 210
no controller = 3.570 = 190

nismo 270R:
12/12 = 3.429 = 191
01/01 = 3.347 = 187
24/24 = 3.635 = 203
01/24 = 3.323 = 186
24/01 = 3.716 = 207
no controller = 3.323 = 186

spoon s2000 on 200 to 50 test:
12/12 = 2.560 = 143
01/01 = 2.683 = 150
24/24 = 2.961 = 165
01/24 = 2.643 = 148
24/01 = 2.642 = 148
06/06 = 2.642 = 148
18/18 = 2.601 = 145
no controller = 2.625 = 147
it seems, using 12/12 brake is the optimum

temporary conclusion:
the optimum brake for each car is different, there is no general setting! 1/1 is faster on some car, slower on other.
the jaguar xjr can stop faster than nismo 270r or spoon integra .......
Not using brake controller can give faster time, on some car.

 

[Scaff]

It seems that nobody test the effect of using different Brake ballance number on GT4 yet.

..........


the optimum brake for each car is different, there is no general setting! 1/1 is faster on some car, slower on other.
the jaguar xjr can stop faster than nismo 270r or spoon integra .......
Not using brake controller can give faster time, on some car.

You may have missed the following post (have a look at the very first post in this thread for a full list of tests and subjects).

Setting Brake Bias

As you say the optimum brake bias setting will vary for each car, dependent on its static weight distribution and weight transfer characteristics.

The post I linked to provides a guide to calculating a starting point in terms of brake bias settings, and may be of interest.

It also needs to be remembered that tests carried out in GT2 will not (unfortunatly) give results that can be transfered to GT4, how the tyres under braking are modelled is very different in each GT game. As the following tests I carried out indicate.

GT - A comparison across the series



I have, however been meaning to carry out some brake bias tests with a car that has significant weight transfer under braking to take a look at the results. Any free time I get I will use to look at this.

From my own experience I also know how difficult it is to get consistent figures out of GT2, one thing that is made much easier in GT4 with the Data Logger.

Regards

Scaff

 

[sucahyo]

As you say the optimum brake bias setting will vary for each car, dependent on its static weight distribution and weight transfer characteristics.

The post I linked to provides a guide to calculating a starting point in terms of brake bias settings, and may be of interest.

From my own experience I also know how difficult it is to get consistent figures out of GT2

Nice link,
But the brake bias link doesn't explain what I need to know, do brake bias function as brake force in GT4? I want to know if using 1/1 is faster or slower than 24/24, or it behave differently on each car like GT2 do.
For bias, in GT2 it seems using 1/24 will get you closer to optimum braking on some car than 24/1. But I maybe wrong ,because I only test it on 4 car. But with hundred car to choose, I don't know where to start.

GT4 maybe have different brake simulation than GT2, so in GT4 you can have general rule for the brake? we have to test each car in GT2.

Using P.E.Op.S. Soft Driver 1.16 on epsxe we can record the video to get the fairly accurate time to 0.0xx second differences, and then we can calculate the braking distance from those time. On 3 times trying, I can get the same braking result up to 2 meters accuracy.

BTW, I don't have GT4, I just curious. Maybe PD will just make the brake setting easier in GT4, because in GT2 brake tuning become trivial if you don't want to test it the hard way.

 

[Scaff]

Nice link,
But the brake bias link doesn't explain what I need to know, do brake bias function as brake force in GT4?

The Brake Bias in GT4 sets both the bias between front and rear brakes and the level of force. 1 being the weakest and 24 being the strongest.

As an example the following settings would all be a 50%:50% ratio between front and rear, but with different levels of brake force.

1 front : 1 rear
12 front: 12 rear
24 front : 24 rear

I want to know if using 1/1 is faster or slower than 24/24, or it behave differently on each car like GT2 do.

The brake bias setting in GT4 operates in a more realistic manner than in any previous version of GT. As in the real world brake bias settings have to be tailored to each car and tested to ensure they are correct.

For bias, in GT2 it seems using 1/24 will get you closer to optimum braking on some car than 24/1. But I maybe wrong ,because I only test it on 4 car. But with hundred car to choose, I don't know where to start.

The brake bias in GT2 is a very blunt tool with little difference to the braking with very different settings.

In the real world setting as extreme as 1:24 or 24:1 would result in a car with very poor braking characteristics, as either the front or rear (depending on the bias settings) would lock long before the opposite end. This would totally defeat the purpose of the brake bias tool, which is to ensure that all four tyres are sharing the braking load equally.

As a starting point for a brake bias setting, the post I originally pointed you to explains all you need, and yes it will need to be looked at for each car.

GT4 maybe have different brake simulation than GT2, so in GT4 you can have general rule for the brake? we have to test each car in GT2.

While a few general rules do exist for brake bias settings, such as:

Brake bias should generally be set towards the front of the car, as weight transfer under braking gives them more grip. So they can do more of the work, they will also then be the first to lock, which is more controlable that if the rears locked first.

However it does depend on what you want to do with the car; if you are setting up for fast laps then the above would be true. If however you are setting a car up for drifting, you want the rears to lock first, so the bias would be set towards the rear.

Again the post I linked to gives general guidelines to provide a bias setting to start with, which significantly cuts down on the amount of testing needed.

Using P.E.Op.S. Soft Driver 1.16 on epsxe we can record the video to get the fairly accurate time to 0.0xx second differences, and then we can calculate the braking distance from those time. On 3 times trying, I can get the same braking result up to 2 meters accuracy.

You can actually get very similar results in GT2 (for the times) just be pausing the replays, which was my old method.

I would argue, however that calculating stopping distances from time is not the most acurate method (but the only one you c an use in GT2).

GT3 and GT4 have a big advantage in the Data Logger, which allows stopping distances to be measured down to the centemetre.

BTW, I don't have GT4, I just curious. Maybe PD will just make the brake setting easier in GT4, because in GT2 brake tuning become trivial if you don't want to test it the hard way.

The brake bias settings in GT4 actually require more work to get set right if you just start from scratch and experimemnt with the settings. A rough calculation based on static weight distribution and estimated weight transfer (again see my linked post) which can then be tweaked through testing is a much quicker method.


In closing I have to say that, unfortunatly, no magic answer exists for brake bias settings in GT4 or the real world. You can get a head start based on static weight distribution, weight transfer, etc; but you can't escape the need to test if you want to truely optomise braking.

You also need to always keep in mind that all brake bias settings are doing is ensuring that each tyre is sharing the braking load equally. What actually determines the optimum stopping distance is not the brakes, but the tyre fitted. Brake bias settings just allow you to make the most of the grip the tyres have. Ultimatly if you need to stop quicker the best route is stickier tyres, as the brake bias is limited by the tyres limits.

Regards

Scaff

 

[sucahyo]

A very detailed explanation, thank you!
About tire grip, so in MR car that usually have stickier tire (bigger diameter, wider) on the rear you will use more rear bias, right?

You GT4 guys have a really nice tool! I wish GT2 have data logger too, all we have is gear speed calculator (tire diameter calculator) from noquarter and optimum gear ratio calculator with optimum shifting suggestion from jmac.

 

[DuckRacer]

Thanks for being cool about it Duck, some may have got all protective.

I would've if you only stiffened the rear by 0.1, but that didn't happen. 👍

One thing I forgot to mention above, while your settings did not allow me to obtain the fastest possiable laptime out of the car, they are damn fine for getting the back of the car out in a controlable manner.

So a big 👍 for that.

Thanks.

 

[Scaff]

A very detailed explanation, thank you!
About tire grip, so in MR car that usually have stickier tire (bigger diameter, wider) on the rear you will use more rear bias, right?

To a degree what you say is correct, but the load on the tyre under braking is just as important. No matter how big or sticky the tyre, if its doesn't have enough load on it, then its not going to help.

With MR cars it does depend on the weight distribution, a lot are around 50:50 so under braking the fronts are going to be loaded more than the rears and the bias would normally still be towards the front of the car.

Some MR cars however have a weight distribution of 40:60 (Lotus Elise is a good example) so even under hard braking the weight transfer may only make it a 50:50 distribution. The result would be a bias to neither the front or rear.

The cars most likely to have a rear bias are RR models, as they have a very high static distribution to the rear it is possiable that even under hard braking the weight is still biased towards the rear. In this case a rear biased brake setting would be possiable.

You GT4 guys have a really nice tool! I wish GT2 have data logger too, all we have is gear speed calculator (tire diameter calculator) from noquarter and optimum gear ratio calculator with optimum shifting suggestion from jmac.

I use the calculator from jmac (and very handy it is) and I have my own gear speed calculator as I have had to calculate mph per 1,000rpm as part of my job for many years.

The Data Logger is a handy tool, but to be honest it could be a lot better, it is still quite limited. It is, however, better than nothing.

Regards

Scaff

 

[Scaff]

I would've if you only stiffened the rear by 0.1, but that didn't happen. 👍

Oh, that would suck so much!

imagine "Hey [insert name here], your settings suck; but if you just stiffen the rear by 0.1 its great."

Now that would be the sort of thing to get you angry.

Regards

Scaff

 

[sucahyo]

My recent test on silvia, 1/24 win against 24/18
Side by side braking duel on silvia, 1/24 vs 24/18

So I think PD already have incorporate the weight transfer and weight distribution in front and rear brake multiplier which is different on each car. I think PD will not expect us to incorporate that when tuning the brake.

 

[Scaff]

My recent test on silvia, 1/24 win against 24/18
Side by side braking duel on silvia, 1/24 vs 24/18

So I think PD already have incorporate the weight transfer and weight distribution in front and rear brake multiplier which is different on each car. I think PD will not expect us to incorporate that when tuning the brake.

Interesting stuff and I have put a reply to the GT2 tests over in that thread. 👍

With regard to GT4, the physics engine is still (as it always has been) biased towards the front wheels. What I mean by this is locking the front wheels will have a much bigger impact on stopping distances than locking the rears.

I have tested a few extreme settings with this in mind.


Aston Martin V8 Vantage '99

Car totally stock, oil change carried out and a brake balance controller fitted.

The car has a static weight distribution of 53 f / 47 r and a crub weight of 1,970 kilos.

The test was a standard 0 - 100 mph brake test at the test track, all settings were tested over six runs and the average stopping distance used.


Results
All settings shown are f / r


No BBC fitted - 85m

BBC Fitted
Default setting 3 / 3 - 85m

Extreme front bias 24 / 1 - 100.5m

Extreme rear bias 1 / 24 - 85.6m

Scaff's setting 5 / 3 - 82.8m

Ducks request 1 3 / 5 - 85.2m

Ducks request 2 5 / - 84.1m

The default and w/o BBC runs posted an identical average distance, which would ten to indicate that the basic defaults appear to still be in use when the BBC is not fitted.

The extreme front bias massively increases the stopping distance, by 15.5m, the car itself feels stable under braking, but the ABS at the front kicks in and the car feels far slower when stopping.

The extreme rear bias results in a small increase in stopping distance, of 0.6m over the default. The car still felt resonable stable under braking, but turning under braking did cause the rear to feel more unstable than with the extreme front bias.

Now an extreme front bias (far beyond what is required) will generally result in a greater increase in stopping distance than an extreme rear bias, as the fronts will almost always be asked to do more of the braking work than the rears. Therefore if the front lock before the rears you will loose more of the grip you need to stop quickly.

However real world experience would lead me to expect a greater increase in stopping distance for the extreme rear bias than we see above, however it would never be as great as the increase from the extreme front bias.

An extreme rear bias would also cause the car to be a lot more unstable under braking on most tracks, the test track is very, very smooth. Try a high speed stop at the end of the Mulsanne with an extreme rear bias and the car will take longer to stop as you need to keep it in a straight line (at least with a DFP, the DS2 helps you a lot here).

So what effect does using my basic brake bias calculation from a few posts ago. I estimated the weight transfer under braking from 100mph to be about 20% as a start (this is just an educated guess) and with the static weight distribution calculated a BBC setting of 5 / 3.

This resulted in a stopping distance of 82.8m, or 2.2m shorter that the default, which translates to about half a cars length in a Vantage.

As you can see incorrect brake bias settings, will at best have lttle or no effect (extreme rear) and at worst, destroy your stopping distance (extreme front).

Get them right however, and you can maximise your tyres potential.

Just remember, for real improvements in stopping distance you need better tyres, and any change in your cars overall weight, ballast and/or ride height and you might need to rethink your brake bias setting.


Regards

Scaff


Edited to add two new figures for Duck, tested 3/5 and 5/5 settings

The 3 / 5 bias showed an increase of 0.2m from default, small enough to be down to driver error or indicate that a slight rear bias does result in a longer stopping distance. More work required here!

The 5/5 bias resulted in a slightly shorter stopping distance of 84.1m; 0.9m shorter than default. Again indicating a step in the right direction.

Hope these are OK Duck

 

[DuckRacer]

1. How do you figure the weight distribution of the Vantage?

2. What do you use/do to calculate the braking distance?
and
3. Could you try setting the Brake balance to 3 / 5, and see what it does? And then 5 / 5 after that?

Sorry for asking so much.

 

[sucahyo]

No BBC fitted - 85m

BBC Fitted
Default setting 3 / 3 - 85m

The default and w/o BBC runs posted an identical average distance, which would ten to indicate that the basic defaults appear to still be in use when the BBC is not fitted.

Interesting, in GT2 all car have BBC defaulted to 12/12. Maybe because of this the time is different on more car.

2.2 meters is significant! I think I have to take the car weight distribution more seriously!. if I don't know the car weight distribution maybe I'll try brake tuning based on smoke and sound..............

 

[Uncle Harry]

Can you do some tests to check benifits around the track. When I race I dont need to come to a full stop. The extra stopping distance may be minor when the better stability in the turn in is factored in to the total lap time.

 

[sucahyo]

I just realize that experimenting brake bias using race brake is a big mistakes, I just found out that racing brake performance varies because it needs to be warmed up and when the brake get warmed the performance change, if the time between using is change, the result also change. This means I can get more accurate result tuning the brake by not using race brake.

GT2 Aston Martin V8 Vantage stock + engine mods.
First run using stock brake: time, calc distance, 300kmph time, 70kmph time
3.922 251 45.810 49.732
3.922 251 01.410 05.332
3.922 251 46.703 50.625

Second run using race brake
4.414 282 42.527 46.941
3.964 253 00.986 04.950
3.840 245 51.505 55.345

third run using race brake
4.449 284 44.191 48.640
3.902 249 02.389 06.291
4.045 258 51.197 55.242
3.963 253 06.479 10.442
3.963 253 52.125 56.088
3.840 245 05.734 09.574
4.005 256 52.495 56.500
3.799 243 06.895 10.694

It seems my calculated distance is a way off. I think I will use your time to make it more accurate.

The brake is cold on the first half lap, the time is about the same 4.4 seconds
when the brake get warmup , the times get better
but because I only use the brake on 2 point in each lap, the brake get the chance to cool down, changing the brake performance. Because I brake on different point on the track, my time get vary. Using stock brake, the time is exactly the same .....

I shouldn't ignore the rules, that race brake need to be warmup..........

Do you need to warmup the racing brake in GT4?