toe discussion

[nomis3613]

Hi,
I'd like to pick apart how the toe settings work in GT4. All contributions welcomed!

TEST METHOD
The FR test car was a Holden Monaro with RM tyres. The FF test car was a Honda Civic with RM tyres. For front toe, I tested acceleration of an FR car, acceleration of an FF car and braking distance. Rear toe testing was done for acceleration of an FR car (ie the driven wheels), braking using the rear wheels and top speed of an FR car.

FRONT TOE THOUGHTS
For rwd cars, I have found the main effect to be the trade-off between turn-in and exit understeer.
Negative toe = less turn in (bad), but less exit understeer (good)
Positive toe = more turn-in, but more exit understeer.
Negative front toe also improves acceleration (remember this is NOT the driven wheels in this case) and braking, but the effect is minimal. (I was surprised that the acceleration and braking was best for -1, I expected these tests to give the best results when the wheels were pointing straight ahead)

For fwd cars, the above "turn-in vs exit understeer" effect is also a factor. But since the front wheels are also needed for acceleration, the far greater effect is on power-down: positive values improve power-down (which effectively reduces exit understeer), so fwd cars benefit from positive front toe (I have found rwd cars prefer a negative or zero value). However, above a certain point (+2 in the Civic I was testing), the increased exit understeer (as seen on rwd) starts to outweigh the increased power-down.

Sure, the improvement in fwd acceleration times are very slight, but around Autumn Ring, the overpowered Civic had much better power-down exiting tight corners.

REAR TOE THOUGHTS
I found the main effect of rear toe to be general under/oversteer. Positive rear toe is like stiffening the front stabiliser, negative is like stiffening the rear. But what about the acceleration/braking/top speed side effects...

...FR power-down is clearly improved with positive rear toe. Braking is too close to call, so I reckon negligable. And the top speed test showed no increase in rolling drag when the wheels are pointing slightly inwards or outwards. Although I didn't test it, I would expect this to mean rear toe has no effect on acceleration for an FF car, since it appears that GT4 does not model rolling drag.

I also had a quick play around with rear toe in a Ruf Yellow Bird. The same basic change to handling was noticed, but the effect was minimal. This makes me think that the main factor for handling in this car is the weight transfer.

 

[Leonidae@MFT]

I've gained better results with rear toe values.

 

[sukerkin]

One thing it will be interesting to pin down is if you can confirm whether power-on toe-out is observable (at the front in FWD's and the rear in RWD's of course ).

 

[nomis3613]

Yo, I've added to the first post with my testing graphs and rambling thoughts about rear toe. Check it out!

Sukerkin, sorry I don't understand what effect you're talking about. Is it something to do with toe-in = stability and toe-out = nervous?

 

[Parnelli Bone]

I've gained better results with rear toe values.

Yea you're all about carefully-set rear toe. I've noticed.

 

[Leonidae@MFT]

Well, our racing oriented teacher ( works as suspension mechanic in Super 2000-class touring car team ) told that rear suspension settings have large impact on how willing the car is to rotate, or how steady it is on the straights.. And I'm willing to take his word for it.

 

[Parnelli Bone]

Yup. I think GT4's tuning info also has some info about rear toe being the setting that makes a greater difference. Personally I never mess with toe unless I'm off-road or I absolutely have to change it to get a car to do what I'd like.

 

[sukerkin]

The effect I was referencing, nomis is the tendency for driven wheels to take on toe-out when power is applied. What I forgot is that RWD is the reverse effect than what is seen in FWD .

I quote from a website of a company that does tracking:

"The toe angle identifies the direction of the tires compared to the centerline of the vehicle. Rear-wheel drive vehicle "pushes" the front tires, as they roll along the road, resistance causes some drag resulting in rearward movement of the suspension arms against their bushings. Most rear-wheel drive vehicles use positive toe to compensate for suspension movement.

Front-wheel drive vehicle "pulls" the vehicle, resulting in forward movement of the suspension arms against their bushings. Most front-wheel drive vehicles use negative toe to compensate for suspension movement."

Note that, to me, Positive Toe is Toe IN and Negative Toe is Toe OUT.

As ever, the more opinions you read, the less clear things get sometimes :

"Below are guidelines for setting toe and how it can affect feel and handling.

Front Toe-Out
Just Right
Reduced understeer at turn-in Improved steering response Counteracts natural tendency for front- and all-wheel-drive cars to toe-in under throttle load

Too Much
Instability during braking Straight-line instability, especially over single-wheel bumps or split-traction surfaces Unrecoverable understeer"

 

[Leonidae@MFT]

And weren't the toe values somehow reversed or some crap like that in GT4?

 

[sukerkin]

Aye, Leo, there was considerable discourse on that at one time .

In particular it was felt that what was Toe IN at the Front was Toe OUT at the Rear, the theory being, I think, that the coders had thought of it in terms relative to the end of the car rather than the direction of travel :faints:.

I really need to get back into this again - it's been a year with no spanner twirling and I miss it!

 

[Parnelli Bone]

And weren't the toe values somehow reversed or some crap like that in GT4?

It's been proven they were definately reversed in GT2. Sucahyo used a certain device we're not supposed to talk about here at GTP to dissemble various parts of that game years ago to prove it. I'll dig up the thread if I can find it...

here it is...

https://www.gtplanet.net/forum/showthread.php?t=73639

 

[nomis3613]

Look out, mega-post ahead!

The effect I was referencing, nomis is the tendency for driven wheels to take on toe-out when power is applied. What I forgot is that RWD is the reverse effect than what is seen in FWD .

Ahhhh... yeah after looking at the acceleration results, I was thinking about exactly the same phenomenon, what a coincidence!

"The toe angle identifies the direction of the tires compared to the centerline of the vehicle. Rear-wheel drive vehicle "pushes" the front tires, as they roll along the road, resistance causes some drag resulting in rearward movement of the suspension arms against their bushings. Most rear-wheel drive vehicles use positive toe to compensate for suspension movement."

I don't think GT4 models this. My acceleration results were best at -1 deg front toe (see later for whether toe is backwards)

"Front-wheel drive vehicle "pulls" the vehicle, resulting in forward movement of the suspension arms against their bushings. Most front-wheel drive vehicles use negative toe to compensate for suspension movement."

Yep, this I saw. Improved accel traction for +ve front toe

As ever, the more opinions you read, the less clear things get sometimes :

"Below are guidelines for setting toe and how it can affect feel and handling.

Front Toe-Out
Just Right
Reduced understeer at turn-in Improved steering response Counteracts natural tendency for front- and all-wheel-drive cars to toe-in under throttle load

Makes sense to me, and seems consistent with what the GT4 scrolling text says. (to me, it seems the guide was written for cars that would never run front toe-in, so the only question is "how much toe-out is too much?". So I assumed that "reduced understeer at turn-in, improved steering response" means that turn-in understeer and steering response are ok, compared with running too much front toe-out)

Too Much
Instability during braking Straight-line instability, especially over single-wheel bumps or split-traction surfaces Unrecoverable understeer"

Yep. The instability comes from the outside rear tyre (inside is unloaded, so far less important) pointing away from the corner, creating oversteer. Can't say I've noticed the effect of bump-steer in GT4, though.

Aye, Leo, there was considerable discourse on that at one time .

In particular it was felt that what was Toe IN at the Front was Toe OUT at the Rear, the theory being, I think, that the coders had thought of it in terms relative to the end of the car rather than the direction of travel :faints:.

Yeah, people thought that it could be backwards because apparently Japanese engineers describe it the other way around. My 2 cents is that rear is definitely the right way around, because:
+ve rear toe = understeer = toe-in
-ve rear toe = oversteer = toe-out

As for front toe, I don't know enough about how it works in combination with the steering (Ackerman, etc) to say whether
-ve front toe = reduced exit understeer = toe-out
matches real-life theory or not. But from my fwd accel testing and how it relates to power-on toe changes, it looks like it's correct.

I really need to get back into this again - it's been a year with no spanner twirling and I miss it!

Go on, get into it! It could be your warm-up for when GT5 comes out in November...

I'll dig up the thread if I can find it...

here it is...

https://www.gtplanet.net/forum/showthread.php?t=73639

Thanks! It's also interesting to see the GT2 default settings, how some cars already have the LSD effect for example.

 

[MadMax]

Correct me if I'm wrong , but
from my experience I know that in GT4 for pure straith line acceleration
the best toe settings for FWD is +4/-4 example 1
and for RWD -4/+4 example 2
AWDs work like RWDs on the toe behalf

Basicly positive toe on the pulling/pushing wheels increases straith line grip and thus acceleration.
And negative toe on non accelerating wheels degreases their drag.

And rear toe affects cornering more than front toe



MadMax

 

[nomis3613]

Hi, I won't diss your theories, whatever works for you! Also, my tuning is aimed at track work, I don't do drag races, so it's interesting to compare theories.

Correct me if I'm wrong , but
from my experience I know that in GT4 for pure straith line acceleration
the best toe settings for FWD is +4/-4 example 1

Basicly positive toe on the pulling/pushing wheels increases straith line grip and thus acceleration.

Yep, 4 deg front toe-in for FWD agrees with my accel testing.

And negative toe on non accelerating wheels degreases their drag.

For the rear, I suspect that GT4 doesn't model rolling drag. But it seems give you a slight straight line benefit if the non-driven wheels are at their "best" toe (in my testing the best braking and RWD accel both occurred at -1 front toe)

and for RWD -4/+4 example 2

Yep. Again, agree on the driven wheels. Personally, I'd do testing before claiming that -4 front was the best for straight line accel.

AWDs work like RWDs on the toe behalf

I reckon that would depend on the VCD.

And rear toe affects cornering more than front toe
MadMax

Depends on the car IMHO. But I agree that rear toe affects handling in all phases of cornering, whereas front toe is only in certain situations and the effect is more subtle. I reckon front toe is still a useful tool in extracting that last ounce of speed!

 

[sukerkin]

The generally accepted theory is that:

Front Toe settings affect the quite important first third of cornering where you set up the line to the apex i.e. initial turn in.

Rear Toe impacts upon acceleration through the apex and the attitude of the car on corner exit i.e. whether understeer or oversteer shows up.

 

[sukerkin]

Once again I'd like to say that it is nice to see someone delving into these matters again. A fresh eye always brings with it the chance to see things that have been overlooked.

 

[nomis3613]

The generally accepted theory is that:

Front Toe settings affect the quite important first third of cornering where you set up the line to the apex i.e. initial turn in.

Rear Toe impacts upon acceleration through the apex and the attitude of the car on corner exit i.e. whether understeer or oversteer shows up.

Just wondering, is that real-life theory or GT4 experience? To me, it feels like rear toe affects the overall stance (including turn-in), but of course this could be a placebo effect...

Once again I'd like to say that it is nice to see someone delving into these matters again. A fresh eye always brings with it the chance to see things that have been overlooked.

awww...thanks! <blushes>

 

[sukerkin]

It is real-world theory, rather than in-game observation, I do confess.

In game it is indeed possible that rear-toe has it's effect all the way through a corner because it is a variable that acts to amplify or reduce understeer, especially when under power.

 

[nomis3613]

I've recently been noticing that large toe values (negative or positive) often work well at low speed, but cause the car to "wander" at high speed. Even rear toe-in (which is meant to stabilise the car) can cause the car to be a handful at high speed.

Also, can someone please explain to me how acceleration causes rear toe-out in a rwd car? I'm guessing that for the front wheels, the angle that the wheel takes when the car is is "dragging" it to accelerate would be caused by the location of the steering link. But what would cause the rear wheels to toe-out? Or is there some other factor which causes better straight line grip for +ve rear toe values?