how break bias affect handling of the car(understeer/oversteer)?

[ekhlious]

I am new to tuning & I watched a lot of tutorial and guides for tuning on YouTube but I cant understand why? what's the physical phenomena/logic behind it when the breaks more biased to the front the car understeer isn't suppose to oversteer by logic?

& as mentioned I am knew to the series if anyone have an answer to one of those questions I would appreciate it a lot deeply :

1- In 4WD cars the torque distribution is it best to be neutral between front and back ?is there a rule for it? if its more biased to front that will induce understeer and vice versa I don't really know or it depends on the cars shape and weight distribution?

2-how to adjust adjust the power ratio and weight ratio in relation to each other I saw a lot of tunes with different ratio values why not leave it 100% all the time what's the significance of changing it ? what's the indication of power/torque curve?

3-is ride height differentiation between the front and rear affects car handling or its just a placebo I saw some youtuber mention it and other not?

 

[eran0004]

Brake bias
Brake bias affects handling under hard braking. To make it more intuitive you can think about what happens when you brake so hard that the wheels are locking. In this case you lose most of the grip from the tyres.

If you lock the front wheels, most of the grip is at the back of the car (behind the center of mass), this creates a very stable situation where the car will tend to self-align so that it goes straight forward.

If you lock the rear wheels, most of the grip is in the front (in front of the center of mass), this creates a very unstable situation where the front tyres will induce a torque on the vehicle around the vertical axis, which causes the car to rotate.

Locking the wheels is kind of the edge cases here, you wouldn't want to brake so hard. But what you're doing with brake bias is basically to determine which edge case you want the car to tend to. With more front bias you get more understeer under braking, with more rear bias you get more oversteer.

4WD torque distribution
It's basically like brake bias, just it's applied during acceleration instead. More front bias gives more understeer during acceleration, and vice versa. Keep in mind that as you accelerate, weight is shifted towards the rear wheels, increasing their grip. So a neutral balance is usually one that has more torque on the rear wheels.

Power/Torque
Power indicates the rate of change of energy; work per unit of time. Any change in speed of a car is a change in energy, so if you want the car to accelerate quickly you want to have a lot of power (alternatively a low amount of mass). Work is equal to force*distance, and torque is the rotational analogue of force.

Spoiler: Power vs torque - which is best?

There is some confusion about the significance of torque and power, you may have heard that "torque is good for acceleration" while "power is good for top speed". Technically it's not incorrect, but it's also not the complete picture. Torque is absolutely good, but the torque figure alone won't tell you anything about how good the engine is for acceleration, because it doesn't account for the whole equation: change in energy per second = force*distance per second, where the torque figure just accounts for the force. The distance per second remains unknown and we can't solve the equation.

Power, on the other hand, does account for the entire equation (that's the whole purpose of power), and the relation between the torque curve and the power curve is actually very simple: power = torque * engine speed. That means torque is a component of power and as such you can absolutely say that "more torque gives better acceleration", because as long as the engine speed remains the same or is increased, the power increases as well. But if you increase the torque while decreasing the engine speed, the power output may actually drop and the performance gets worse.

So what you should be looking for in a racecar engine is primarily the power curve. The more power, the better. But wait, there is more! Unless you have a CVT gearbox, where you can continually run the engine at peak power, the shape of the power curve matters as well. During the acceleration the engine will operate at a range of rpms, and you want the engine to produce as much power as possible throughout that range. An engine with a very peaky power curve needs a gearbox with very closely spaced gears, so that the engine can perform close to peak power throughout the acceleration. An engine with a more flat power curve can handle a gearbox with the gears spaced further apart, and it's usually easier to drive as well because it's not as important that you stay in the correct gear.

Spoiler: More on power vs torque

One reason why some people are confused with respect to power vs torque is probably because high torque cars sometimes do better than high power cars in drag races. That makes it easy to think that acceleration is about torque - not power. But it's actually down to the shape of the power curve, because when the engine produces a lot of torque at the low engine speeds it tends to give a very flat power curve. If you put such a car against one with more power but a very peaky power curve, the average power output of the first car may actually be greater than that of the second car. So the "torque" car didn't win because it produced more torque, but because it had a greater average power output (all else being equal).

Suspension tuning
...is not my cup of tea. I have no idea how it works.

 

[ekhlious]

Brake bias
Brake bias affects handling under hard braking. To make it more intuitive you can think about what happens when you brake so hard that the wheels are locking. In this case you lose most of the grip from the tyres.

If you lock the front wheels, most of the grip is at the back of the car (behind the center of mass), this creates a very stable situation where the car will tend to self-align so that it goes straight forward.

If you lock the rear wheels, most of the grip is in the front (in front of the center of mass), this creates a very unstable situation where the front tyres will induce a torque on the vehicle around the vertical axis, which causes the car to rotate.

Locking the wheels is kind of the edge cases here, you wouldn't want to brake so hard. But what you're doing with brake bias is basically to determine which edge case you want the car to tend to. With more front bias you get more understeer under braking, with more rear bias you get more oversteer.

4WD torque distribution
It's basically like brake bias, just it's applied during acceleration instead. More front bias gives more understeer during acceleration, and vice versa. Keep in mind that as you accelerate, weight is shifted towards the rear wheels, increasing their grip. So a neutral balance is usually one that has more torque on the rear wheels.

Power/Torque
Power indicates the rate of change of energy; work per unit of time. Any change in speed of a car is a change in energy, so if you want the car to accelerate quickly you want to have a lot of power (alternatively a low amount of mass). Work is equal to force*distance, and torque is the rotational analogue of force.

Spoiler: Power vs torque - which is best?

There is some confusion about the significance of torque and power, you may have heard that "torque is good for acceleration" while "power is good for top speed". Technically it's not incorrect, but it's also not the complete picture. Torque is absolutely good, but the torque figure alone won't tell you anything about how good the engine is for acceleration, because it doesn't account for the whole equation: change in energy per second = force*distance per second, where the torque figure just accounts for the force. The distance per second remains unknown and we can't solve the equation.

Power, on the other hand, does account for the entire equation (that's the whole purpose of power), and the relation between the torque curve and the power curve is actually very simple: power = torque * engine speed. That means torque is a component of power and as such you can absolutely say that "more torque gives better acceleration", because as long as the engine speed remains the same or is increased, the power increases as well. But if you increase the torque while decreasing the engine speed, the power output may actually drop and the performance gets worse.

So what you should be looking for in a racecar engine is primarily the power curve. The more power, the better. But wait, there is more! Unless you have a CVT gearbox, where you can continually run the engine at peak power, the shape of the power curve matters as well. During the acceleration the engine will operate at a range of rpms, and you want the engine to produce as much power as possible throughout that range. An engine with a very peaky power curve needs a gearbox with very closely spaced gears, so that the engine can perform close to peak power throughout the acceleration. An engine with a more flat power curve can handle a gearbox with the gears spaced further apart, and it's usually easier to drive as well because it's not as important that you stay in the correct gear.

Spoiler: More on power vs torque

One reason why some people are confused with respect to power vs torque is probably because high torque cars sometimes do better than high power cars in drag races. That makes it easy to think that acceleration is about torque - not power. But it's actually down to the shape of the power curve, because when the engine produces a lot of torque at the low engine speeds it tends to give a very flat power curve. If you put such a car against one with more power but a very peaky power curve, the average power output of the first car may actually be greater than that of the second car. So the "torque" car didn't win because it produced more torque, but because it had a greater average power output (all else being equal).

Suspension tuning
...is not my cup of tea. I have no idea how it works.

WOW That's very enlighten, I am Impressed on how much knowledge you guys know & I wander how you got to know all of this & I wish I discovered this forum and the whole site three years earlier it would made a Hugh difference for me playing the game because the game doesnt really explain anything & even their Youtube channel doesnt & there wasnt a good tutorials about these kind of stuff on YouTube for too long , thanks anyway..

 

[eran0004]

WOW That's very enlighten, I am Impressed on how much knowledge you guys know & I wander how you got to know all of this & I wish I discovered this forum and the whole site three years earlier it would made a Hugh difference for me playing the game because the game doesnt really explain anything & even their Youtube channel doesnt & there wasnt a good tutorials about these kind of stuff on YouTube for too long , thanks anyway..

Engineering Explained has a lot of nice videos about vehicle physics

https://youtube.com/user/EngineeringExplained

 

[ILLEAGLE_34]

WOW That's very enlighten, I am Impressed on how much knowledge you guys know & I wander how you got to know all of this & I wish I discovered this forum and the whole site three years earlier it would made a Hugh difference for me playing the game because the game doesnt really explain anything & even their Youtube channel doesnt & there wasnt a good tutorials about these kind of stuff on YouTube for too long , thanks anyway..

Check out @Tidgney driving school on YouTube he has like 20 episodes in great detail on most if not all the info you have been looking for. Hope this helps. ( sorry not sure how to add a direct link ) Cheers

 

[CBH]

WOW That's very enlighten, I am Impressed on how much knowledge you guys know & I wander how you got to know all of this & I wish I discovered this forum and the whole site three years earlier it would made a Hugh difference for me playing the game because the game doesnt really explain anything & even their Youtube channel doesnt & there wasnt a good tutorials about these kind of stuff on YouTube for too long , thanks anyway..

We know a lot of Knowledge about Gran Turismo games over the years my friend, but sadly with GT Sport it is like a ghost town in this GTS tuning forum, when you want help about tuning.

 

[MasterGT]

I am new to tuning & I watched a lot of tutorial and guides for tuning on YouTube but I cant understand why? what's the physical phenomena/logic behind it when the breaks more biased to the front the car understeer isn't suppose to oversteer by logic?

& as mentioned I am knew to the series if anyone have an answer to one of those questions I would appreciate it a lot deeply :

1- In 4WD cars the torque distribution is it best to be neutral between front and back ?is there a rule for it? if its more biased to front that will induce understeer and vice versa I don't really know or it depends on the cars shape and weight distribution?

2-how to adjust adjust the power ratio and weight ratio in relation to each other I saw a lot of tunes with different ratio values why not leave it 100% all the time what's the significance of changing it ? what's the indication of power/torque curve?

3-is ride height differentiation between the front and rear affects car handling or its just a placebo I saw some youtuber mention it and other not?

Tuning a car, and various types of cars, requires a bit of compromise, which is why you may need to adjust someone else's tune to suit your driving style. For example, I like a very stable car, others may like to add power oversteer, to swing out the rear end of the car, to get around a sharp corner at a sharper angle. I am too hamfisted to be able to control doing that well. Others may be willing to take the time practice, to get better at it. The ability to do that is partly controlled by ride heights (your #3). If you want more oversteer, raise the rear end; if you want more stability, lower and soften the rear end suspension.

Some tuners lower the front and raise the rear, to add rake to the body, for more downforce. I don't do that, but you can raise or lower a car to affect handling. You can go too low / high because, eventually, you probably will start affecting handling through the centre of gravity. This is a compromise.

My weekly events are run with cars at their default weight and power levels. I do that because we all need to know how to control weight. You won't learn that as quickly if you keep lowering the weight or increasing the HP. Understanding shifting weight of a car is essential to learning how to drive most cars. Nearly every car in Sport comes with enough power to have fun with other good drivers, especially if everyone drives the same car. (If you want a safe environment where you can learn to drive better and faster, please join us Mondays or Wednesdays, depending on your time zone. Tuning is recommended and encouraged.)

Take a look at the Mitsubishi GTO Twin Turbo tune that I just posted. The car weighs as much as 29 yards of railway track. You will struggle with that car if you don't control its weight shift well. However, with 937 lbs sitting on each corner, the 285 HP will not even spin Comfort Hard tires under its power, so there is that about it.

If you drive an AWD car, some of the power driving the car forward goes to the front tires. If you send too much power to the front, it not only can cause understeer, but it can also wear out your tires sooner. You can learn to take care of your tires while driving, to make them last longer, but your tune can help too. However, the split is a compromise. Some tuners compromise by sending as much power to the rear wheels as possible, to make the car drive more like an FR. On some tracks or some surfaces, such as dirt, you may want more towards the front tires. A compromise.

 

[ekhlious]

Tuning a car, and various types of cars, requires a bit of compromise, which is why you may need to adjust someone else's tune to suit your driving style. For example, I like a very stable car, others may like to add power oversteer, to swing out the rear end of the car, to get around a sharp corner at a sharper angle. I am too hamfisted to be able to control doing that well. Others may be willing to take the time practice, to get better at it. The ability to do that is partly controlled by ride heights (your #3). If you want more oversteer, raise the rear end; if you want more stability, lower and soften the rear end suspension.

Some tuners lower the front and raise the rear, to add rake to the body, for more downforce. I don't do that, but you can raise or lower a car to affect handling. You can go too low / high because, eventually, you probably will start affecting handling through the centre of gravity. This is a compromise.

My weekly events are run with cars at their default weight and power levels. I do that because we all need to know how to control weight. You won't learn that as quickly if you keep lowering the weight or increasing the HP. Understanding shifting weight of a car is essential to learning how to drive most cars. Nearly every car in Sport comes with enough power to have fun with other good drivers, especially if everyone drives the same car. (If you want a safe environment where you can learn to drive better and faster, please join us Mondays or Wednesdays, depending on your time zone. Tuning is recommended and encouraged.)

Take a look at the Mitsubishi GTO Twin Turbo tune that I just posted. The car weighs as much as 29 yards of railway track. You will struggle with that car if you don't control its weight shift well. However, with 937 lbs sitting on each corner, the 285 HP will not even spin Comfort Hard tires under its power, so there is that about it.

If you drive an AWD car, some of the power driving the car forward goes to the front tires. If you send too much power to the front, it not only can cause understeer, but it can also wear out your tires sooner. You can learn to take care of your tires while driving, to make them last longer, but your tune can help too. However, the split is a compromise. Some tuners compromise by sending as much power to the rear wheels as possible, to make the car drive more like an FR. On some tracks or some surfaces, such as dirt, you may want more towards the front tires. A compromise.

thank you very much for taking the time to reply, its was very enlightenment .. but allow me to ask why raising the height of the back of the car increase the oversteer isnt that will allow more body roll on the back as it gives more room for the springs on the back & more body roll on the back = more understeer?


I have another question actually why increasing the the Toe-in on the back of the car increase the oversteer from what I understand while cornering if toe-in is applied the outside wheel will be oriented towards the corner & the inside wheel will be the opposite of that angle(toe-in) but wait a second isnt the most of the weight (due to weight transfer)will be focused on the inside wheel which makes it doing most of work but its oriented the other direction and that suppose to cause more understeer instead??
& why toe angle affect if its applied to the back(as YouTube tutorials suggest)?

of course I want to join your weekly events will look it up but I am focused now more on the single player..

 

[bread82]

I was going to write some explanations here, but eran0004 has it well covered! I do have something to add on brake bias.

Brake Bias
I usually drive FR cars and often put the brake bias a little rearwards as:

i) It helps the car turn in on corner entry when trail braking (mild oversteer). Many cars on factory settings understeer a bit too much for me.

ii) For events with tyre wear, the front tyres tend to wear faster as they are taking a lot of the steering and braking effort. This applies even to FR cars where the rears are doing the acceleration. Once worn, you get more understeer so it helps to add rear brake balance at the start of the race and/or as the wear occurs to both eliminate the understeer and equalise tyre wear, the tyres last longer between pit stops that way.👍

iii) Note that when you change brake balance, then press the brakes, the top of the braking indicator bar will be red. The more extreme the balance adjustment, the more red. This is similar to the throttle bar when you use traction control. I assume this means the red part of the brake is not used. You are reducing brake pressure. The brakes are overall weaker, but you gain a more favourable balance of car handling. This can still make you faster overall.

The units of force and exact numbers below, are fictional, but I think it works like this, where changing balance always weakens one brake, rather than strengthening one. Adjust rearward and you don't get more rear brake, you get less front brake.

e.g. Brake balance 0 F 100/R 100 Overall 200
Brake balance 2 Rear F 80/R 100 Overall 180 but more oversteer
Brake balance 2 Front F 100/R 80 Overall 180 but more understeer

I also think most front brakes start as more powerful than the rears (this is true in real world). I have put them both as "100" just for simplicity. But it might actually be more like "F 150/R 100 Overall 150", as default.

I drive without ABS and look to lock up the front wheels under braking, then adjust rearward until I get the handling I like. If I can't lock up wheels any more then I know I've sacrificed brake performance. This is tyre/car dependent. I haven't tested but a stock VW beetle on RSS tyres probably will notice a reduction in brake performance since the tyres are so sticky and could cope with lots of brake force. A Group1 race car on Comfort Hards (lol) may have such good brakes, and such poor tyres that reducing brake pressure by moving the balance still means the crappy tyres can be locked up, so no loss in performance (the tyres are the limiting factor).

@ekhlious , if you want to learn more about suspension tuning in general, check out Scaff's GT4 guide and Motor City Hami's GT5(or was it 6?) guide. These are available in the relevant GT games' Tuning forums and most will apply to GT Sport.

GT Sport has practically no telemetry so it's hard to tune numerically, you have to do it by feel (and lap times!). It requires patience. I'd advise spending quite a lot of time on your favourite car, and always run several (I usually do 5 or even more) laps after changing a setting, use a short track so you're not there all day, I like Tsukuba. You need repeat laps since there's always human variation and it's easy to mess up/absolutely win on a single lap and put it down to the setting when it was just luck. This is "boring", some people hate it and others fall in love with the detail and the car, looking to shave another 0.2 seconds off their personal best.

Keep old tunes in different tabs, that way you can go back to them if you mess something up. Sometimes after tuning a while you'll actually go back to an old tune and be faster as your driving style has evolved. When you're tuning the car for a long while, the car also tunes you

​

 

[MasterGT]

thank you very much for taking the time to reply, its was very enlightenment .. but allow me to ask why raising the height of the back of the car increase the oversteer isnt that will allow more body roll on the back as it gives more room for the springs on the back & more body roll on the back = more understeer?


I have another question actually why increasing the the Toe-in on the back of the car increase the oversteer from what I understand while cornering if toe-in is applied the outside wheel will be oriented towards the corner & the inside wheel will be the opposite of that angle(toe-in) but wait a second isnt the most of the weight (due to weight transfer)will be focused on the inside wheel which makes it doing most of work but its oriented the other direction and that suppose to cause more understeer instead??
& why toe angle affect if its applied to the back(as YouTube tutorials suggest)?

of course I want to join your weekly events will look it up but I am focused now more on the single player..

Raising the rear end adds to the pendulum effect of the car's weight thereby adding to oversteer. I lower and soften the rear end of many cars, to control oversteer.

I am not qualified to thoroughly answer your toe questions at this time. But toe is another setting that may need compromising. FF cars may need toe-in on the front and toe-out on the back. AWD cars may need other unusual settings. It depends. Be willing to experiment, to learn more.

 

[ekhlious]

I was going to write some explanations here, but eran0004 has it well covered! I do have something to add on brake bias.

Brake Bias
I usually drive FR cars and often put the brake bias a little rearwards as:

i) It helps the car turn in on corner entry when trail braking (mild oversteer). Many cars on factory settings understeer a bit too much for me.

ii) For events with tyre wear, the front tyres tend to wear faster as they are taking a lot of the steering and braking effort. This applies even to FR cars where the rears are doing the acceleration. Once worn, you get more understeer so it helps to add rear brake balance at the start of the race and/or as the wear occurs to both eliminate the understeer and equalise tyre wear, the tyres last longer between pit stops that way.👍

iii) Note that when you change brake balance, then press the brakes, the top of the braking indicator bar will be red. The more extreme the balance adjustment, the more red. This is similar to the throttle bar when you use traction control. I assume this means the red part of the brake is not used. You are reducing brake pressure. The brakes are overall weaker, but you gain a more favourable balance of car handling. This can still make you faster overall.

The units of force and exact numbers below, are fictional, but I think it works like this, where changing balance always weakens one brake, rather than strengthening one. Adjust rearward and you don't get more rear brake, you get less front brake.

e.g. Brake balance 0 F 100/R 100 Overall 200
Brake balance 2 Rear F 80/R 100 Overall 180 but more oversteer
Brake balance 2 Front F 100/R 80 Overall 180 but more understeer

I also think most front brakes start as more powerful than the rears (this is true in real world). I have put them both as "100" just for simplicity. But it might actually be more like "F 150/R 100 Overall 150", as default.

I drive without ABS and look to lock up the front wheels under braking, then adjust rearward until I get the handling I like. If I can't lock up wheels any more then I know I've sacrificed brake performance. This is tyre/car dependent. I haven't tested but a stock VW beetle on RSS tyres probably will notice a reduction in brake performance since the tyres are so sticky and could cope with lots of brake force. A Group1 race car on Comfort Hards (lol) may have such good brakes, and such poor tyres that reducing brake pressure by moving the balance still means the crappy tyres can be locked up, so no loss in performance (the tyres are the limiting factor).

@ekhlious , if you want to learn more about suspension tuning in general, check out Scaff's GT4 guide and Motor City Hami's GT5(or was it 6?) guide. These are available in the relevant GT games' Tuning forums and most will apply to GT Sport.

GT Sport has practically no telemetry so it's hard to tune numerically, you have to do it by feel (and lap times!). It requires patience. I'd advise spending quite a lot of time on your favourite car, and always run several (I usually do 5 or even more) laps after changing a setting, use a short track so you're not there all day, I like Tsukuba. You need repeat laps since there's always human variation and it's easy to mess up/absolutely win on a single lap and put it down to the setting when it was just luck. This is "boring", some people hate it and others fall in love with the detail and the car, looking to shave another 0.2 seconds off their personal best.

Keep old tunes in different tabs, that way you can go back to them if you mess something up. Sometimes after tuning a while you'll actually go back to an old tune and be faster as your driving style has evolved. When you're tuning the car for a long while, the car also tunes you

​

thanks for sharing that I rally appreciate it and sorry for the late reply...
I understand every thing you said except for this statement:"I drive without ABS and look to lock up the front wheels under braking, then adjust rearward until I get the handling I like. If I can't lock up wheels any more then I know I've sacrificed brake performance." .. I know what ABS & locking up wheels mean but the brake performance sacrifice I didnt get it?

Also I looked up for motor city tunes for GT6 and its just tunes for GT6(tuning garage) without explanations and I couldn't find Scaff's GT4 guide

 

[CBH]

thanks for sharing that I rally appreciate it and sorry for the late reply...
I understand every thing you said except for this statement:"I drive without ABS and look to lock up the front wheels under braking, then adjust rearward until I get the handling I like. If I can't lock up wheels any more then I know I've sacrificed brake performance." .. I know what ABS & locking up wheels mean but the brake performance sacrifice I didnt get it?

Also I looked up for motor city tunes for GT6 and its just tunes for GT6(tuning garage) without explanations and I couldn't find Scaff's GT4 guide

Look at post #2 here in GT6 Tuning Guide 1.15 .

 

[ekhlious]

Look here GT6 Tuning Guide 1.15 .

Thanks 😊 a million times will read it carefully

 

[ekhlious]

For anyone whos still struggling to understand the suspension setup I have found this amazing YouTube channel called XF Motorsports
and here is a sample video talking about :(Springs and Anti-Roll bars / Sway bars)

thanks for everyone here who helped me understanding (fordlaser,MasterGT & eran0004)

​

 

[CBH]

For anyone whos still struggling to understand the suspension setup I have found this amazing YouTube channel called XF Motorsports
and here is a sample video talking about :(Springs and Anti-Roll bars / Sway bars)

thanks for everyone here who helped me understanding (fordlaser,MasterGT & eran0004)

​

No problem and I hope to see you when Gran Turismo 7 comes out, because there will be a lot of help in that game than GTS.

 

[bread82]

@ekhlious
What I mean is that, with ABS off, you'll lock (turn red) wheels under braking. With default brake balance 0, this is usually the front wheels locking alone, or all four eventually lock but the fronts lock first. If the fronts lock by default, when you move the brake balance rearwards to improve handling, eventually the front brakes will be weakened so much they no longer lock.

This means the front tyres aren't being used to their maximum any more. They could cope with more braking force as they haven't locked yet. Thus overall braking performance is less.

However, this situation may still be favourable as:
i) You will prefer the handling, there is less understeer with a more rearward brake bias.
ii) Locking the fronts is tricky and required delicate brake control without ABS (threshold braking). Once locked and red, the tyre gives very little grip as it's skidding, which will give mega understeer. Racing tyres in particular give a load of grip and then lock and suddenly let go.