Author Topic: Brake Bias and Tire Changes  (Read 3898 times)

[SJ]Peter Enqvist

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Brake Bias and Tire Changes
« on: August 15, 2007, 02:50:12 am »
There's 2 features in GTL that I'm not sure I fully understand the usefulness of.  The first one is the ability to adjust the brake bias from the cockpit.  Now I'm not saying it's useless, I'm just saying I don't fully understand it.  I know that real life race cars also have that feature.  The only time I ever use it in GTL is when I'm working on setting up a car.  It's faster to get the brake bias right by adjusting it while you drive and seeing what affect it has, rather than constantly going into the garage to adjust it.  After I have my setup done I never change it.  I would think there must be instances in a race where you would want to change brake bias.  Tire wear, changes in grip level of the track (does that even happen in GTL??), etc.  Does anyone use the brake bias adjustment during races, and if so, which way do you adjust it?

The other thing I don't understand is why it's possible to change the front tires and the rear tires seperately in a pitstop.  I would think that it would do more harm than good.  Even with a puncture I'd want to change all 4 tires (unless the puncture happened on the first lap).  I tried changing just the front tires on the Mercedes 300SL after 20 laps while practicing Monaco and it was terrible.  The car fishtailed a lot after that.  Does anyone know of an instance where you'd want to change just the fronts or just the rears?

[SJ]Jarkko Rantajoki

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Re: Brake Bias and Tire Changes
« Reply #1 on: August 15, 2007, 02:59:52 am »
There's 2 features in GTL that I'm not sure I fully understand the usefulness of.  The first one is the ability to adjust the brake bias from the cockpit.  Now I'm not saying it's useless, I'm just saying I don't fully understand it.  I know that real life race cars also have that feature.  The only time I ever use it in GTL is when I'm working on setting up a car.  It's faster to get the brake bias right by adjusting it while you drive and seeing what affect it has, rather than constantly going into the garage to adjust it.  After I have my setup done I never change it.  I would think there must be instances in a race where you would want to change brake bias.  Tire wear, changes in grip level of the track (does that even happen in GTL??), etc.  Does anyone use the brake bias adjustment during races, and if so, which way do you adjust it?

The other thing I don't understand is why it's possible to change the front tires and the rear tires seperately in a pitstop.  I would think that it would do more harm than good.  Even with a puncture I'd want to change all 4 tires (unless the puncture happened on the first lap).  I tried changing just the front tires on the Mercedes 300SL after 20 laps while practicing Monaco and it was terrible.  The car fishtailed a lot after that.  Does anyone know of an instance where you'd want to change just the fronts or just the rears?


About the brake bias during races.. sometimes i use a lot of brake in the rear in the start of the race, when the tires start to die i move it a little bit to the front to make it more comfortable to drive.. Dont know how "right" it is but seems to work. Ive never fiddled with changing only rears or fronts, i usually decide between no tires change or take new tires depending on the situation in race and current tire condition.

[SJ]Mario-C

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Re: Brake Bias and Tire Changes
« Reply #2 on: August 15, 2007, 03:50:36 am »
I change the brake bias on the fly on certain tracks,especially ones with hard braking to a hairpin from a long straight I swing it to the front,then balance it more towards the middle for normal corners.All done by feel really and as pdsm says the state of the rubber.

[SJ]Peter Enqvist

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Re: Brake Bias and Tire Changes
« Reply #3 on: August 15, 2007, 04:28:07 am »
I swing it to the front,then balance it more towards the middle for normal corners.


Oh that's interesting, I never thought of that.  I've always just tried to find a compromise for the whole track.

[SJ]FAR

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Re: Brake Bias and Tire Changes
« Reply #4 on: August 15, 2007, 06:41:38 am »
Here is my idea:

The most important reason to adjust the brake-bias is the fuel-load. If the car is getting less weight with every lap the brake-balance will move also. Normally you have to adjust the brake bias during the race more to the rear... :?: hm..sounds funny for you?...no it isn`t...under braking the weight (aerodynamic weight and the normal weight) moves to the front of the car and there you need more brakes to stop the car faster...less weight during the race means less moving weight to the front and so you have to adjust the brake bias more to the rear.

You can try it easily on a straight of the track...Just drive full speed there, set the transmission to neutral (to turn off the Differential influence) and brake hard until the wheels lock up...if they first lock up at the front, you adjust it more to the rear, and the same otherwise...to keep the car stable under braking i normally have more brakes at the front...
Not possible with GT Legends but with GTR2: The brake-temperature helps also. I try to have the front-brake-temperature 50-100degrees hotter than the rear.

And like Mario does, i adjust even the brake-balance for special corners during a lap on some tracks.

This all works for me, if it can help you ,it would be fine

Frank
 :gtg:


[SJ]Dion Holzheimer

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Re: Brake Bias and Tire Changes
« Reply #5 on: August 15, 2007, 07:58:50 am »
I generally run as much rear bias as i can and if its a downhill braking section i overlap the braking with a bit of gas. Same if im braking over decent bumps. This stops rears from locking and allows me to run deep into corners under brakes without locking fronts. I can see how adjusting brake bias on the fly would be very helpful however i just find it easier to compensate with driving techniques rather than fiddling around trying to find the correct button.

[SJ]Nailz

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Re: Brake Bias and Tire Changes
« Reply #6 on: August 15, 2007, 08:38:16 am »
i've changed just fronts in the mini many times, as the cars so light theres hardly any rear wear, and it stops the wee motor from pushing through corners!!!

[SJ]mgoran

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Re: Brake Bias and Tire Changes
« Reply #7 on: August 15, 2007, 08:53:25 am »

I generally run as much rear bias as i can and if its a downhill braking section i overlap the braking with a bit of gas. Same if im braking over decent bumps. This stops rears from locking and allows me to run deep into corners under brakes without locking fronts. I can see how adjusting brake bias on the fly would be very helpful however i just find it easier to compensate with driving techniques rather than fiddling around trying to find the correct button.



 :yep:     its my way , too ...

[SJ]dirtyvfr

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Re: Brake Bias and Tire Changes
« Reply #8 on: August 15, 2007, 09:26:53 am »
interesting, i've alway thought of the brake balance in another way

seeing as the fuel tanks on most cars historically were nearer the rear of car, then when the car is running a full fuel tank the centre of gravity ( static ) moves further to the rear of the car, so i move the brake balance back a bit, under braking the effective centre of gravity ( dynamic ) moves forward and with a heavier car the weight transfers are also larger, so large in fact that the front tyres can't cope and lock up, locked up wheels don't stop anything, but there is still enough weight at the rear of the car to do a bit of slowing down, thus the reason i move the brake balance rearward when the car is running a full load and when the car lightens up i move the brake balance forwards ( not that i've done it much and only in the capri i think )

please note the above is only for braking in a straight line and i normally find a long straight and switch to the side view, so i can see the cars wheels, but can't see where i'm going, brake balance for trail braking and mid corner braking balance is another matter.

 

     

 


[SJ]CasparGTL

  • rFactor Test Driver
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Re: Brake Bias and Tire Changes
« Reply #10 on: August 15, 2007, 12:28:38 pm »
Very interesting thread! Thanks for all the detailed opinions guys.

I haven't looked into it that much and this is what I do sofar;

I like my brake balance as much to the rear as possible.
I learned that in GPL because there , overcoming the huge default understeer could, among others, be overcome by changing the brake balance to the rear. Many cars I run at 50& there.

In GTL the variety of cars is much bigger of course and my first love was and perhaps still is the 911 (yeah yeah Cas we know, geeez!)
In that car, because it's so twitchy I use the brakes a LOT for turning and also to use the chosen suspension setup to the max.
Heavy front braking gives a lot of stopping power for hairpins and such, I understand that, but still, I like to use the last part of braking in the first stage of steering, even for hairpins (Oulton Park)
It's a habit from GPL I think but I like it.
I understand better and better now when I went overboard and the brake bias is to much to the rear and I also have to look into what Dion says. Most of the time I have my left foot ready or lightly on the brakes to correct mistakes in a corner and though I also use throttle AND brake in corners there's a lot to be learned for me there.
I have never changed brake bias while driving and also wondered what that would bring but now I understand, so thanks.
I don't even know how to do it, haha, will find it though.
Changing it every part of a lap is a bit much for my nerves I think but I will definitely look into it, so thanks for that too!

Caspar.



[SJ]Kristof Huyck

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Re: Brake Bias and Tire Changes
« Reply #13 on: August 15, 2007, 05:12:16 pm »
The other thing I don't understand is why it's possible to change the front tires and the rear tires seperately in a pitstop.  I would think that it would do more harm than good.  Even with a puncture I'd want to change all 4 tires (unless the puncture happened on the first lap).  I tried changing just the front tires on the Mercedes 300SL after 20 laps while practicing Monaco and it was terrible.  The car fishtailed a lot after that.  Does anyone know of an instance where you'd want to change just the fronts or just the rears?


Well, I guess probably everybody changes all 4 tires, so this feature isn't that useful. There are however cars that have much higher rear tires wear like De Tomaso Pantera for example. You could only change the rear tires in such a case.
However, it takes about the same time to change 2 or 4 tires in GTL (a glitch?), so in fact I never change 2 tires only...

[SJ]Pierre61

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Re: Brake Bias and Tire Changes
« Reply #14 on: August 15, 2007, 06:36:55 pm »
Great thread, and great article!
I'm still very much a Newb at this stuff, but the most salient piece of info I ever read on this subject was along the lines of....
Race braking is the opposite of road car braking... rather than a slow application of the brake from light to heavy... as you do in a road car... the wheels are turning so much faster that you apply full welly at the beginning of the braking cycle and reduce pressure to null at the corner apex.

... or something like that :)

[SJ]Earnhardt

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Re: Brake Bias and Tire Changes
« Reply #15 on: August 15, 2007, 08:42:48 pm »
I've always had the bias as far to the rear as comfy. This allows the front to 'concentrate' more of the tire's grip on turning instead of braking. The amount of engine brake also changes the balance.

Dialing it in on the fly is the only way  :shh:  because the balance will change during the race for many different reasons.


[SJ]2shedz

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Re: Brake Bias and Tire Changes
« Reply #16 on: August 15, 2007, 09:13:12 pm »
I'm from the school of 'if it stops and turns without me going off its fine  :ner ner: as for changing it on the fly ARE YOU MAD   :jawdrop: its all i can do to remember what gear i need to be in, IF i can remember what corners coming up next and thats provided i am actually at the track i think i am at  :tut:
:ted:

[SJ]Peter Enqvist

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Re: Brake Bias and Tire Changes
« Reply #17 on: August 15, 2007, 09:28:24 pm »
I'm from the school of 'if it stops and turns without me going off its fine  :ner ner: as for changing it on the fly ARE YOU MAD   :jawdrop: its all i can do to remember what gear i need to be in, IF i can remember what corners coming up next and thats provided i am actually at the track i think i am at  :tut:
:ted:


LOL!!

[SJ]D

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Re: Brake Bias and Tire Changes
« Reply #18 on: August 25, 2007, 11:15:13 pm »
    :hand up:

   Edit: I'm removing this Temporarily; until I can put together an adequate set of
           Instructions.......More of a When & How to use
           which Rule,..change the Constant/Base,..and oddly enough, when to apply the
           Calc in reverse
                                   :?:

          The Formulae still work great,..but I didn't want somebody beating themselves in
          the head over some bad numbers.

Ride on Josephine                                                                                   :peace out:
« Last Edit: August 29, 2007, 08:52:59 pm by SJ_D »

[SJ]dirtyvfr

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Re: Brake Bias and Tire Changes
« Reply #19 on: October 13, 2007, 07:31:55 pm »
brake pressure is a very good way of setting up your brakes, seeing as even the G25 is well off the mark for braking, as brakes in a car are controlled by pressure and not travel.

you can reduce the brake pressure (it's different for each car) and you have to take into account fuel loads, but playing with the brake pressure works very very well.