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Rank: On the Podium
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#1 Posted : Thursday, October 22, 2015 9:45:15 AM(UTC)



If you have anything to add to it let me know and I'll be glad to do so.

Thanks



First Rule: Fix the end of the car that has the problem. If it's the rear sliding around don't go adjusting the front. Start with adjusting the back end to stabilize it first. You can then go up or down in unison to stiffen or soften the car.



Tires and Temperature

Getting the correct temperature/pressure combination is like fitting together a big puzzle. Stiffer spring = more temperature and stiffer roll bars = higher temperature and on and on. It all fits together and the tires are the only thing we have direct control of. It's often the most overlooked part of tuning yet it is the most important.

I'll use the recommendations that I have gathered from Pirelli for temperature as some manufacturers differ +/- 10° F. The optimal grip for a tire will differ by what compound you put onto the vehicle. The softer the tire the lower the temperature needed for optimal grip.

PSI needs to be 30-35 when hot. I generally settle with 33.

Temperature range can be from 180° to 210° F. A softer tire will lose grip more rapidly once it gets past 210° than a harder compound.

How does tire temperature relate to pressures?

Higher pressure = Lower temperature
Lower pressure = Higher temperature


This works in small amounts. On FWD cars in the game you can have a really high PSI in the rear and it will slide all over the place.

Adjustments Decrease Understeer Decrease Oversteer
Front Tire Pressure Higher Lower
Rear Tire Pressure Lower Higher


Some of the below quotes do not apply to FM5 with the high camber ratings.

Quote:
Uniform rules no matter what

Give the tires 3 laps to warm up before looking at telemetry.

You should never have more than 20° between the inner portion of the tire and the outer with the inside always being hotter.

You should never have more than 25° between the front and rear of the car

Alignment:

Quote:
Keep in mind you want no more than 20° difference between the inside and outside of the tire with the inner 1/3 always being hotter (10°-15° are good numbers). Make sure you look when actual load is on the tires going through a corner and the tires have had proper time to heat up (3 laps minimum). Sometimes on a track with turns mainly loading one side of the car the tires will heat up uneven. This is normal.


Camber
You always want negative camber

Negative = More inside
Positive = More outside

There is a sweet spot in this setting that usually doesn't change unless you move the Caster around too much once everything is set. You also always want more camber in the front than the rear. Rear camber isn't as necessary as those tires don't turn and I want them with a touch of negative camber when throttle is applied on exit.

Toe
Front toe favors a positive number (more responsive and better turn in) between .1° and .5°. Anything above .3° will cause excessive drag in the straights and gets really bad above 160mph.
Rear toe favors a negative number and becomes more responsive through turns at 1°. However anything over 2° and the back end loses a lot of stability in acceleration and braking. On bumpy tracks any amount of rear toe will cause the car to lose stability and you will have to make corrections even in a straight line costing you time.

EDIT: To clarify you shouldn't use more than .3 degrees in either direction unless the circumstance is extreme.

Caster
Allows the tires to roll with the chassis giving a larger contact patch through a turn. It also helps to balance the temperature of the tires on tracks with predominant left/right turns.

A larger number here will also help absorb bumps on the track while decreasing stability as too much caster causes the tires to wander a bit.

I personally like a really high Caster (5.5-7.0) in the lower classes but on tracks with longer sweeping turns less caster is better.. Most cars aren't sensitive to caster changes.

Adjustments Decrease Understeer Decrease Oversteer
Front Wheel Camber More Negative More Positive
Rear Wheel Camber More Positive More Negative
Front Wheel Caster More Positive More Negative

Anti Roll Bars

Anti roll bars control how much side to side roll a car has. In theory you would want to minimize body roll as much as possible. This is especially true in the higher classes but on occasion in FM3 some body roll helped things. I guess we will see in FM4. The end of this one is long winded but helps to understand it all.

Rear ARB soften = decrease oversteer or increase understeer
Rear ARB stiffen = decrease understeer or increase oversteer


Understanding what the ARB's do

"Limiting the lean of the body is good because it means that when you take a quick set into a turn, that the body isn't still moving sideways after the tires are at their limits. Otherwise you turn in quickly, the tires grip, then the body finally finishes leaning, when it stops, the tires lose grip."

"It limits camber changes. The camber directly impacts the angle at which the tire cross section meets the road and thus controls lateral grip. As the suspension compresses the camber angle generally changes relative to the chassis. With a normal McPherson strut that hasn't been lowered, the camber goes from positive to more negative as the lower A arm swings out straight, and then back to positive as it swings up. That swing up into positive camber is BAD. At that point the chassis is already leaned over so the tire may be starting to roll onto its sidewall. Changing the camber even more positive is just nasty. A big sway bar will prevent the body roll in the first place, and prevent the suspension compression on the outside which causes the positive camber change relative to the chassis."

"Here's where it gets really tricky: If decreasing the size of the rear bar doesn't help enough, the next thing you do is increase the size of the front bar. When the outside front compresses in a corner, it causes the inside front to compress and may actually lift that tire completely off the ground. The car is now sitting on 3 tires and guess where the weight that was on the inside front goes? Outside front? Some of it. The rest goes to the inside rear where we need more grip. The total weight of the car hasn't changed. It's just been redistributed, and a sway bar at one end, actually transferred weight to the other end of the car. Increasing the front bar then translates into more motive grip at the rear, and thus more acceleration"

Springs & Ride Height

From speaking with Dan the spring tuning and adjustments have changed drastically from FM3 to FM4. Every car is now different based upon what it is in reality as opposed to just one generic suspension being stuck under every vehicle like Forza titles in the past. (his direct words were not all suspensions are the same and the same springs weights don't do the same thing on every single car)

Any change in the spring rate will change the ride height due to the rate of spring deflection. They also change the compression(bump) and deflection(rebound) ratings of the shocks.

I like using my springs to control the suspension travel and balance the weight of the vehicle. Aero also affects the weight on the car and needs to be figured in. Some tracks require a softer spring while others require stiffer. I have went away from using the below formula but will leave it here as a baseline since some like it. I just reduce the stock spring setting by about a 1/4 on front and rear for my base tune.



Ride Height
Keep this as low as possible without the car bottoming out



Damping (shocks)

The extension when the tire is unloaded (force back out) = REBOUND
The compression of a shock (making it smaller) = BUMP

Braking
Under braking the front axle will compress while the rear will rebound. As the weight shifts the front axle will have a higher velocity than the rear which is good because the front should settle before the rear. If the front does settle too quickly the tires in the front will lock a little premature and the same for the rear. Brake bias only masks the problem and moves it to a different portion of the track.

Acceleration
Under acceleration the rear axle will compress while the front will rebound (think of a see-saw). On a RWD for example if the rear squats before the torque reaches peak it reduces the time the driver has to feather the throttle as the tires begin to break loose. Try to balance the compression against the required grip of the torque. FRONT REBOUND SHOULD BE FASTER THAN REAR COMPRESSION.

FWD is different in a sense. For acceleration increasing the front rebound will give more grip initially while increasing rear rebound increases a sustained level of grip.





Downforce and Braking

Downforce
More at rear = more understeer and a stable back end
More at front = more oversteer and increased turn in.

More downforce = less speed in straights, more speed through cornering.

Don't forget that any downforce adjustment = a spring adjustment to compensate for the added weight. Especially at higher speeds.

Braking

Braking pressure is a preference of the driver in my experience.
Your brake bias controls understeer and oversteer while braking.

More front bias = more understeer and can bind the front tires up to where you can't trail brake if you prefer to.
More rear bias = more oversteer and can cause the rear tires to lock up faster than the front which is really bad. Will cause the car to spin. This can also be a preference as some like to go early in fast out and some find it easier to brake later and trail brake through the corner. Those two can create a full scale argument.



Differential Settings

Differential settings increase the amount of lock your inside wheel has while turning. At 100% both the tires turn at the same speed which on a rear differential creates oversteer (on FWD it eliminates torque steer). A higher differential will allow you to use the throttle to help turn around a corner but can cause mid-exit oversteer.

On deceleration when you lift off of the throttle one tire locks faster than the other. This can cause the back end to want to kick out over the locked tire in extreme settings (under 15%). A lower setting does help things and the further apart the accel and decel are on the same differential the more unstable the car seems to get in my experience.

Edited by user Friday, October 23, 2015 12:39:07 PM(UTC)  | Reason: Not specified

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#2 Posted : Thursday, October 22, 2015 9:45:36 AM(UTC)





  • Camber seems to be lower than FM5 and back down into the -2.5 maximum range of previous games.
  • Caster is preference, I like an easier turn in so mine is under 4.0 a lot of the time.
  • Springs softer than standard.
  • Ride height doesn't appear to be slammed in my experience so far.
  • Rebound still in higher numbers. 9.5 to max.
  • Bump is still under 2.5 and generally under 2.






Edited by user Thursday, October 22, 2015 1:54:29 PM(UTC)  | Reason: Not specified

Rank: C-Class Racing License
#3 Posted : Thursday, October 22, 2015 10:10:27 AM(UTC)
And I just got done copying and pasting the whole thing from 4 for a friend who is just starting. Lol. Thanks for putting in the work. This is better than me trying to explain it to him
Rank: A-Class Racing License
#4 Posted : Thursday, October 22, 2015 3:27:31 PM(UTC)
The brake bias slider has been fixed, FACT!
Rank: B-Class Racing License
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#5 Posted : Thursday, October 22, 2015 3:35:34 PM(UTC)
This is the guide I have been using. It has helped alot. I copy and pasted it to a text file and typed in the corner info in the picture. Made it easier to jump to. Thanks Worm.
FM1 = New XBox / FM2 = New XBox 360 / FM5 = New XBox One
............................................Racing Inspires.........
Rank: C-Class Racing License
#6 Posted : Thursday, October 22, 2015 3:40:17 PM(UTC)
I thought higher caster (6.5-7.0) equaled sharper, easier turn-in?
Been racing since Forza 1...2005... NOT 2007 like it say's above.
Rank: On the Podium
#7 Posted : Thursday, October 22, 2015 3:55:11 PM(UTC)
Originally Posted by: gtFOOTw Go to Quoted Post
The brake bias slider has been fixed, FACT!


Will fix


Originally Posted by: JoeDiesle Go to Quoted Post
I thought higher caster (6.5-7.0) equaled sharper, easier turn-in?


More response but more effort required. Will create a weird push in the car where it just won't turn if too high.
Rank: D-Class Racing License
#8 Posted : Thursday, October 22, 2015 6:59:03 PM(UTC)
Worm, would you comment more on the ranges of the sliders you have mentioned in other threads. It didn't sound like you wanted to elaborate but it would be nice if you did please.

Edited by user Friday, October 23, 2015 3:32:33 PM(UTC)  | Reason: Not specified

Rank: Driver's Permit
#9 Posted : Friday, October 23, 2015 1:15:44 AM(UTC)
Originally Posted by: BIG W0RM 80 Go to Quoted Post



Tires and Temperature

Getting the correct temperature/pressure combination is like fitting together a big puzzle. Stiffer spring = more temperature and stiffer roll bars = higher temperature and on and on. It all fits together and the tires are the only thing we have direct control of. It's often the most overlooked part of tuning yet it is the most important.



Just want to clarify has this been miss read u say
Stiffer spring= more temp and stiffer roll bars = higher temp that's the same thing or was one ment to be pressure
Rank: X-Class Racing License
#10 Posted : Friday, October 23, 2015 5:04:07 AM(UTC)
Originally Posted by: Ballbags14 Go to Quoted Post
Originally Posted by: BIG W0RM 80 Go to Quoted Post



Tires and Temperature

Getting the correct temperature/pressure combination is like fitting together a big puzzle. Stiffer spring = more temperature and stiffer roll bars = higher temperature and on and on. It all fits together and the tires are the only thing we have direct control of. It's often the most overlooked part of tuning yet it is the most important.



Just want to clarify has this been miss read u say
Stiffer spring= more temp and stiffer roll bars = higher temp that's the same thing or was one ment to be pressure


No he is saying that higher spring settings OR higher anti-roll bar settings will result in higher tire temperature when under way. This means that you need to adjust your tire pressure so that overall tire temperature when racing remains the same.

Basically, if you adjust the springs or roll bars one way, you may also find yourself tweaking pressure down the road.

W0RM - here is another useful link for helping with over/understeer: LINK!]

The link does take into account some real world stuff that Forza clearly hasn't modeled, but the concepts are valid.

I really like the little coffee paper picture you have there for over/understeer - it's very clear and easy to use. I have it on my computer somewhere but I'm going to 'steal' it again.
Rank: Racing Permit
#11 Posted : Friday, October 23, 2015 7:18:02 AM(UTC)
Originally Posted by: gtFOOTw Go to Quoted Post
The brake bias slider has been fixed, FACT!


So does this mean that what the slider does is actual representation now?
Shneeb108 / Racing SIM Tools Member
Shneeb
Rank: A-Class Racing License
#12 Posted : Friday, October 23, 2015 10:17:42 AM(UTC)
Originally Posted by: ShneebnaMRR108 Go to Quoted Post
Originally Posted by: gtFOOTw Go to Quoted Post
The brake bias slider has been fixed, FACT!


So does this mean that what the slider does is actual representation now?

Yes. Slider to the left increases front bias. Slider to the right increases rear bias.

Rank: On the Podium
#13 Posted : Friday, October 23, 2015 11:29:33 AM(UTC)
Mega camber (>-2.5) still works on a lot of cars and is awful in others. I've even seen in work with one car on one track and not on another with same car/same build.
Rank: On the Podium
#14 Posted : Friday, October 23, 2015 12:42:38 PM(UTC)
Braking is horrendous with high camber though.

Also, I don't like flow charts and diagrams because there are so many variables it could be. Someone could say they are understeering and messing with roll bars when they are just driving like a donkey or their springs are too stiff.
Rank: On the Podium
#15 Posted : Friday, October 23, 2015 3:33:29 PM(UTC)
Originally Posted by: BIG W0RM 80 Go to Quoted Post
Braking is horrendous with high camber though.

Also, I don't like flow charts and diagrams because there are so many variables it could be. Someone could say they are understeering and messing with roll bars when they are just driving like a donkey or their springs are too stiff.


Never noticed the braking getting worse with or without it. But I'll have to consider it now if a car is acting up.
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#16 Posted : Saturday, October 24, 2015 1:51:41 AM(UTC)
Quote:
Keep in mind you want no more than 20° difference between the inside and outside of the tire with the inner 1/3 always being hotter (10°-15° are good numbers). Make sure you look when actual load is on the tires going through a corner and the tires have had proper time to heat up (3 laps minimum). Sometimes on a track with turns mainly loading one side of the car the tires will heat up uneven. This is normal.


I'll quote what I posted in the Camber thread. It may have just been a side-effect of the particular car I was tuning but camber changes had little to no effect on tyre temps at all.


Originally Posted by: PJTierney Go to Quoted Post

While doing my first "serious" tune tonight I discovered something interesting.

In previous games when I did Camber tuning I primarily based my final numbers on tyre heat, having the insides about 5-10 degrees warmer than the outsides.

While trying that method tonight I noticed that initially my values were near even with stock settings. Adding more negative camber should have caused a greater temperature shift, but at the end of my next session I noticed the temperatures were pretty much identical to before despite changing by 1.5 degrees.

Instead, I've now decided to tune my Camber based on how the outside tyres behave mid-corner, attempting to get them as close to 0.0 under load as possible without going over. Personally I don't like to spend too much time on camber tuning as I can barely feel the differences but this looks to be how I'll approach Camber tuning in the future.

Granted, it could be a side effect of the specific car I was using (BMW Z4 GTE) but I figured I'd share my thoughts nonetheless.



Also, if you'e up for adding links to additional guides and resources, I recommend this troubleshooter. I used it as a complement to your Forza Motorsport 4 guide back in the day and it was quite effective.


Originally Posted by: ShneebnaMRR108 Go to Quoted Post
Originally Posted by: gtFOOTw Go to Quoted Post
The brake bias slider has been fixed, FACT!


So does this mean that what the slider does is actual representation now?


There's a simple way to test this:

  • Go to Test Drive.
  • Switch to a Chase camera and look to your left/right.
  • Drive up to a speed of about 100mph
  • Slam on the brakes.
  • Take note of which tyre locks first.
  • If the front locks first move the bias to the rear by about 10%
  • Brake test again and see which wheel locks up first.


From my research it's working as intended, the further back I move the brake bias, the earlier the rear tyres lock in relation to the front.


Originally Posted by: BIG W0RM 80 Go to Quoted Post

Originally Posted by: JoeDiesle Go to Quoted Post
I thought higher caster (6.5-7.0) equaled sharper, easier turn-in?


More response but more effort required. Will create a weird push in the car where it just won't turn if too high.


By "effort" do you mean in terms of you turning the wheel/stick or that it'll push mid-corner?

If it's the former then there won't really be any downsides of max caster to controller users. I know HCR Motorhead uses max Caster on all his tunes and he regularly tops the X/P-Class leaderboards.

Edited by user Saturday, October 24, 2015 2:00:05 AM(UTC)  | Reason: .

Rank: On the Podium
#17 Posted : Saturday, October 24, 2015 1:54:02 PM(UTC)
Quote:
Make sure you look when actual load is on the tires going through a corner and the tires have had proper time to heat up (3 laps minimum). Sometimes on a track with turns mainly loading one side of the car the tires will heat up uneven. This is normal.


Follow-up question on this. When checking tyre data under load, should I be looking at the inside tyre or the outside tyre? If I'm turning right for example, the inner portion of the right tyres will be hot, but that will also mean that the outer portion of the left tyres are hot. Same regarding camber angles.
Rank: Racing Permit
#18 Posted : Sunday, October 25, 2015 6:52:15 AM(UTC)
Quote:
Originally Posted by: BIG W0RM 80 Go to Quoted Post

Originally Posted by: JoeDiesle Go to Quoted Post
I thought higher caster (6.5-7.0) equaled sharper, easier turn-in?


More response but more effort required. Will create a weird push in the car where it just won't turn if too high.


By "effort" do you mean in terms of you turning the wheel/stick or that it'll push mid-corner?

If it's the former then there won't really be any downsides of max caster to controller users. I know HCR Motorhead uses max Caster on all his tunes and he regularly tops the X/P-Class leaderboards.


This is simplified somewhat: With zero caster, the front tires pivot on the contact patches. All steering input results in tire turning. Positive caster moves the point of rotation in front of the contact patch. With more caster, some steering input that previously contributed to front tire turning will instead add more front tire lean in the direction of the turn. The tops of the front tires tip left for left hand turns and vice-versa. This can be helpful because the outside front tire is loaded when braking & turning-in, and the extra inward lean adds to negative camber which can give better contact for that tire. It also helps a little on the inside because the lean of the tire offsets "unnecessary" camber on that side. So higher caster can give better grip, but very high caster can result in less crisp or less responsive turn-in.

So by effort, I think what is meant is that you have to turn the steering wheel farther to produce the same amount of tire turn. In a game with purely linear steering, you might not care as much. However and compared to low speeds, the FM games already reduce the amount of front tire response for the same amount of steering input at high speeds. This happens even when all assists are off. Combining this non-linear response with caster effects, high-PI cars can push through entry to high speed sweeps when caster is too high.

Edited by user Sunday, October 25, 2015 11:16:16 AM(UTC)  | Reason: typos & clarity

Rank: R-Class Racing License
#19 Posted : Tuesday, October 27, 2015 6:29:46 PM(UTC)


I would like to point something out... Car weight, tire width, tire compound, tire pressure, spring ratio, ARB stiffness, simulation ON/OFF, etc... Does not effect tire temperature, it will idle at 210 on a straight and fall a bit, but it will be anywhere from 211 to 220 in corners and then quickly back to 210 degrees on the straight.

Now there is change in feel with settings obviously.
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#20 Posted : Wednesday, October 28, 2015 12:38:01 AM(UTC)
Originally Posted by: Manual Clutch Go to Quoted Post


I would like to point something out... Car weight, tire width, tire compound, tire pressure, spring ratio, ARB stiffness, simulation ON/OFF, etc... Does not effect tire temperature, it will idle at 210 on a straight and fall a bit, but it will be anywhere from 211 to 220 in corners and then quickly back to 210 degrees on the straight.

Now there is change in feel with settings obviously.


I have noticed this too; outside of locking the tyres or getting power oversteer my tyre temps rarely move from 210-215 regardless of how I tune.
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#21 Posted : Wednesday, October 28, 2015 3:32:58 AM(UTC)
Originally Posted by: PJTierney Go to Quoted Post
I have noticed this too; outside of locking the tyres or getting power oversteer my tyre temps rarely move from 210-215 regardless of how I tune.


That is the range I have seen for sport and race tires. I would need to double check, but if memory serves, normal tires run at 170 and street tires at 190 degrees F.

Also, temps and pressures appear to stabilize quickly, often by the end of the first lap, but it really takes about 5 minutes for them to start feeling like they have full grip.
Rank: Driver's Permit
#22 Posted : Wednesday, October 28, 2015 5:08:53 AM(UTC)
Originally Posted by: PJTierney Go to Quoted Post
Originally Posted by: Manual Clutch Go to Quoted Post


I would like to point something out... Car weight, tire width, tire compound, tire pressure, spring ratio, ARB stiffness, simulation ON/OFF, etc... Does not effect tire temperature, it will idle at 210 on a straight and fall a bit, but it will be anywhere from 211 to 220 in corners and then quickly back to 210 degrees on the straight.

Now there is change in feel with settings obviously.


I have noticed this too; outside of locking the tyres or getting power oversteer my tyre temps rarely move from 210-215 regardless of how I tune.




My tire temperature will change more when I increase or decrease pressure but I haven't noticed that big of a change with springs and ARBs. My temps are usually low 200s or higher 190s. But a question I have is Worm said the tire pressure should be between 30 and 35 psi when warm, But i usually find my tires at a lower pressure when warm like 29 or 30. And i set my tire pressure to around 26 or 26.5. But it seems i get the most grip with this lower pressure, or am I to low and need to change spring or damping settings?
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#23 Posted : Wednesday, October 28, 2015 5:14:46 AM(UTC)
Higher pressure = Lower temperature
Lower pressure = Higher temperature

This has me confused shouldn't higher pressure result in higher temperature, and Lower pressure result in Lower temperature? Or am I missing something?
Rank: R-Class Racing License
#24 Posted : Wednesday, October 28, 2015 9:19:29 AM(UTC)
Originally Posted by: SPECIES 9 Go to Quoted Post
Higher pressure = Lower temperature
Lower pressure = Higher temperature

This has me confused shouldn't higher pressure result in higher temperature, and Lower pressure result in Lower temperature? Or am I missing something?


Nope. I'll try to explain.

Softer tires gives you a bigger tire patch which means more friction.



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#25 Posted : Wednesday, October 28, 2015 1:54:23 PM(UTC)
It's actually the more flexing of the sidewall that increases temperature much more than the contact patch but still the same result.


Species 9, go get a sp00n and bend it back and forth. How hot does it get? That is what the sidewalls on the tires do when you drive.
Now do it with a knife that isn't so easy to bend, less heat huh?

Edited by user Wednesday, October 28, 2015 1:55:03 PM(UTC)  | Reason: Not specified

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