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Rank: Driver's Permit
#101 Posted : Wednesday, April 9, 2014 7:32:47 AM(UTC)
This was greatly appreciated - truly helps a newbie to racing & Forza 5.
Rank: Racing Permit
#102 Posted : Monday, April 14, 2014 10:30:22 AM(UTC)
Mr. Doctor (DaDoctor) Here's a tip for beginning with base tune in adjusting Spring Rates after installing the Race package on a vehicle. This is from my spreadsheet I'll forward to you later in a e-mail. This is what I start all my builds from and again, this is just a base setup!

To figure out Spring Rate: (Weight of vehicle X Percent of weight distributed) X distribution multiplier (I use anywhere from 0.55 - 0.85) then divide this answer by 2.

For example, I'll show you what I came up with when I began building the 1993 Nissan GT-R. The car's weight is at 3348lbs and the weight distribution is 57% front/43% rear. So your formula will work out like this 3348(0.57) = 1908.3 mulitplied by my multplier of 0.70 (70%) which = 1335.8 and then divided by 2 and this gives me my starting FRONT spring rate of 667.9. To find the REAR spring rate,I of course multiplied the car weight of 3348 by 0.43 and then followed the formula through to 503.8. So you can see I started my base spring rate at 667 FRONT/503 REAR and began working from there.

The mulitplier of 0.55 - 0.85 is dependant on how soft or stiff I want to begin tweaking the spring rate. 85% of total stiffness is the max I will go but then again understand what I choose may be different from what other racers/tuners might choose. Also, what works for me might not always work or be preferable to the other racers and as I'm certain you noticed in reading the forums, everyone out there will use their own calculations or simply choose to what the game uses as default once the full-race packages are installed. OH - and as many tuners have also pointed out, each track can and may require different setups too. My base setup for the GT-R didn't feel comfortable at all at Stadtplatz (Bernese Alps) but was rock-solid at Sebring and Top Gear. Hit me up sometime 'Doctor' and we'll get to starting you on a base setup.
Rank: B-Class Racing License
#103 Posted : Monday, April 14, 2014 2:28:10 PM(UTC)
whats the secret to finding the perfect shift points?
Rank: Racing Permit
#104 Posted : Monday, April 14, 2014 3:41:27 PM(UTC)
Originally Posted by: Mike V 1987 Go to Quoted Post
whats the secret to finding the perfect shift points?


A part of tuning in which I am still trying to figure out correctly. In FM4, using the tickmarks on the analogue display, I was teaching myself to shift at the RPM where the car was making its maximum horsepower. What I miss in FM5 is I can no longer read the spec sheet where it showed where the car made max horsepower and torque at its respective RPMs. If a car is generating 300 horsepower at 6500 RPM and has a 7000 RPM redline, I try to shift right within a few ticks of the 6500 RPM mark because after that and one is just over-revving the engine, though I'm not certain if this makes any difference in Forza. Another trick I've tried is using the telemetry screen, watch where your horsepower begins to drop and at which RPM this is at and try to shift just before this mark. It takes many test laps and free-play runs where I'll watch replays of my race, using telemetry and even using pause and the RT button to slowly move forward a frame so I can see where in my RPM's do I begin losing horsepower.

When it comes to downshifting in corners (and I've screwed this up many times) I try to downshift as the RPM's fall just below the max torque threshold. Again, I use telemetry to find where I lose torque. My idea here is, and I'm certain many others on here will find that I'm undeniably crazy for this, I want to use torque to pull out of a tight corner to get back to speed (The first right corner at Circuit De Spa comes to mind here). As others have said: it comes down to feel.

Rank: D-Class Racing License
#105 Posted : Tuesday, April 15, 2014 5:29:04 PM(UTC)
I have a question about tuning for optimal tire pressure. I keep reading how you should warm the tires up for four or so laps, get a reading, and then adjust. But given that most races are nearly finished by the fourth lap, how does this help? Wouldn't that mean that for the majority of the race your tire pressure is going to be off? Or is this method for endurance races and not your average career or multiplayer race?
Rank: A-Class Racing License
#106 Posted : Wednesday, April 16, 2014 7:04:57 AM(UTC)
Originally Posted by: TheBadJesus Go to Quoted Post
I have a question about tuning for optimal tire pressure. I keep reading how you should warm the tires up for four or so laps, get a reading, and then adjust. But given that most races are nearly finished by the fourth lap, how does this help? Wouldn't that mean that for the majority of the race your tire pressure is going to be off? Or is this method for endurance races and not your average career or multiplayer race?


It typically takes minimum of 1 hard lap to bring to decent temperature and 2 laps for temperatures to stabilize. I would say 3 minutes of hard driving. Optimal tire pressure is good for extended hot lapping sessions and in private multiplayer sessions lasting more than 2 laps. It is generally good to have tire pressures optimized for any use.

Typically the temperature rise is 4 degrees from cold to hot. Therefore if my warm target is 32 psi, I set cold tire pressure at 28 psi. This rule works in most cases.

Having optimal temperature is good but one can cook the tires or make mistakes easily which would completely negate tire fine tuning. Cleaner driving is of higher priority.
"Racing is life. Anything before or after . . . is just waiting." Steve McQueen, LeMans '71
Rank: Racing Permit
User is suspended until 11/22/2041 10:48:55 AM(UTC)
#107 Posted : Wednesday, April 16, 2014 7:30:17 AM(UTC)
Originally Posted by: GRD 4 3L Go to Quoted Post
Originally Posted by: TheBadJesus Go to Quoted Post
I have a question about tuning for optimal tire pressure. I keep reading how you should warm the tires up for four or so laps, get a reading, and then adjust. But given that most races are nearly finished by the fourth lap, how does this help? Wouldn't that mean that for the majority of the race your tire pressure is going to be off? Or is this method for endurance races and not your average career or multiplayer race?


It typically takes minimum of 1 hard lap to bring to decent temperature and 2 laps for temperatures to stabilize. I would say 3 minutes of hard driving. Optimal tire pressure is good for extended hot lapping sessions and in private multiplayer sessions lasting more than 2 laps. It is generally good to have tire pressures optimized for any use.

Typically the temperature rise is 4 degrees from cold to hot. Therefore if my warm target is 32 psi, I set cold tire pressure at 28 psi. This rule works in most cases.

Having optimal temperature is good but one can cook the tires or make mistakes easily which would completely negate tire fine tuning. Cleaner driving is of higher priority.


+1

Rank: A-Class Racing License
#108 Posted : Monday, April 21, 2014 10:12:45 AM(UTC)
So I saw a post by Tyrant that said a car was "hill" tuned (For Prague and Alps).... what does this entail.

I have a S800 Viper that is great anywhere but it is killing me at Prague. (and I mean killing me) The car specs and details below.
So what does hill tuning entail? The car is awesome at LeMans, Bathurst, Indy GP, Spa etc and pretty descent all around. But I'm complete failure at Prague. It really doesn't like the uphill left (bridge embankment gets me all the time. The dip right on the area that over looks the city I have to come way off. I've got no downforce to add, no wider tires... I tried a bunch of persons tunes Raceboy's, ONR Lee Campbell's, Ones called Grip, and Some person who put a god awful Turbo on a Viper (sacrilege). I did not after inspecting each that there was a theme of larger rims for grip tunes. The larger rims did help out. But I'm wondering if there is something more...

Should I be going to a stiffer suspension? and If i do that do I need to then change the ARBs, Rebound and Bump? (Build was me and PTG -Rosney was the mastermind behind the suspension settings, Diff and based off of items i found all over this forum of does and do nots)

So I guess in other words when you find a base tune - what differences do you make to to compensate for tracks. Do you have a rhyme and reason, or do you just tweak a little at a time one way or the other But specifically how in the heck do I make this car handle on Prague and Bernese Alps?

Open tune for your enjoyment and knowledge of how the car is set up specifically. It's not a LB car but its a great all round car on the flat circuits easy top 500 most tracks are 300 or better. I've done a 3:57 at LaSarthe so its pretty fast.
S800 2013 viper GTS
836hp
747lb ft
2731lbs
50%
8.5l

Aspiration Conversion:
Centrifugal supercharger

Engine:
Sport intake
Race fuel
Race ignition
Race exhaust
Race valves
Race engine block
Race pistons

Platform and handling:
Race brakes
Race suspension
Race ARBs front and back
Race roll cage
Race weight reduction

Drivetrain:
RaceDriveline
Race diff

Tires and Rims:
Race compound
Upgrade front 305/30r18
Upgrade rear 365/30r19
Multi-Piece Rims BBS - RS-GT

Tuning:
Tires: 28.5/ 28.5
Gearing is stock (n/a)
Chamber f/r -3.8/-3.0
Toe (f/r) = 0.0/0.0
Caster = 3.0
ARBs (f/r) = 30.02/35.06
Springs (f/r) = 668.1/740.1
Height (f/r) = 3.9 / 4.7
Rebound = 10.9 /11.4
Bump = 3.8/4.3
Aero full = 122/ 337
Brake balance = 50%
Brake pressure = 120%
Diff accel = 30%
Diff decel = 10%


edited with my findings after trying on my own to get some more grip out of this car

So because grip tunes seem to have larger rim sizes I went with that as starters.

I figured that a stiffer springs would help but I has suffering from understeer going up the hill so I went +75 on the front and +100 on the rear.

Changed castor +1. And worked on alignment. .2/ .4 I figured positive on the rear to help push the car through the turn up the hill?

Am I on the right path or am I heading down a rabbit hole?
I sort of am but I know that it can be a puzzle , and I'm wondering if it was just and alignment issue. Or should I have been doing arbs?

Edited by user Monday, April 21, 2014 8:06:33 PM(UTC)  | Reason: Not specified

Rank: A-Class Racing License
#109 Posted : Monday, April 21, 2014 2:38:18 PM(UTC)
Originally Posted by: Mike V 1987 Go to Quoted Post
whats the secret to finding the perfect shift points?


I like to go to old LeMans and run the straight with telemetry on. Looking at HP. The straight makes it easy to concentrate on the numbers. If I'm having a hard time I will do this and then save replay and off I want to save replay to watch the HP and figure out the power curve, ill go to Indy oval so I can save the replay easier and the lap is pretty short. Ill just run every gear out to rev limit. Make notes. On rpm versus HP.

Then if the track is ok for the car ill practice shifting there. But I usually use mulsanne straight for that.

Wormburner say try and match shifting to make the shift so the HP is close to matching as possible.

At a minimum there isn't a point in running past the HP curve where HP falls off so that is typically how I shift. Unless the track dictates otherwise, no need to upshift if your about to brake. Vipers like to be shifted under 6k. But I usually run 4th a little past redline as the difference between 4th and 5th after shift is so great I lose speed in the shift. So I go a little further so it's a closer match
Rank: A-Class Racing License
#110 Posted : Tuesday, April 22, 2014 4:21:33 AM(UTC)
Originally Posted by: PervasiveFall8 Go to Quoted Post
So I saw a post by Tyrant that said a car was "hill" tuned (For Prague and Alps).... what does this entail.

I have a S800 Viper that is great anywhere but it is killing me at Prague. (and I mean killing me) The car specs and details below.
So what does hill tuning entail? The car is awesome at LeMans, Bathurst, Indy GP, Spa etc and pretty descent all around. But I'm complete failure at Prague. It really doesn't like the uphill left (bridge embankment gets me all the time. The dip right on the area that over looks the city I have to come way off. I've got no downforce to add, no wider tires... I tried a bunch of persons tunes Raceboy's, ONR Lee Campbell's, Ones called Grip, and Some person who put a god awful Turbo on a Viper (sacrilege). I did not after inspecting each that there was a theme of larger rims for grip tunes. The larger rims did help out. But I'm wondering if there is something more...

Should I be going to a stiffer suspension? and If i do that do I need to then change the ARBs, Rebound and Bump? (Build was me and PTG -Rosney was the mastermind behind the suspension settings, Diff and based off of items i found all over this forum of does and do nots)

So I guess in other words when you find a base tune - what differences do you make to to compensate for tracks. Do you have a rhyme and reason, or do you just tweak a little at a time one way or the other But specifically how in the heck do I make this car handle on Prague and Bernese Alps?

Open tune for your enjoyment and knowledge of how the car is set up specifically. It's not a LB car but its a great all round car on the flat circuits easy top 500 most tracks are 300 or better. I've done a 3:57 at LaSarthe so its pretty fast.
S800 2013 viper GTS
836hp
747lb ft
2731lbs
50%
8.5l

Aspiration Conversion:
Centrifugal supercharger

Engine:
Sport intake
Race fuel
Race ignition
Race exhaust
Race valves
Race engine block
Race pistons

Platform and handling:
Race brakes
Race suspension
Race ARBs front and back
Race roll cage
Race weight reduction

Drivetrain:
RaceDriveline
Race diff

Tires and Rims:
Race compound
Upgrade front 305/30r18
Upgrade rear 365/30r19
Multi-Piece Rims BBS - RS-GT

Tuning:
Tires: 28.5/ 28.5
Gearing is stock (n/a)
Chamber f/r -3.8/-3.0
Toe (f/r) = 0.0/0.0
Caster = 3.0
ARBs (f/r) = 30.02/35.06
Springs (f/r) = 668.1/740.1
Height (f/r) = 3.9 / 4.7
Rebound = 10.9 /11.4
Bump = 3.8/4.3
Aero full = 122/ 337
Brake balance = 50%
Brake pressure = 120%
Diff accel = 30%
Diff decel = 10%


edited with my findings after trying on my own to get some more grip out of this car

So because grip tunes seem to have larger rim sizes I went with that as starters.

I figured that a stiffer springs would help but I has suffering from understeer going up the hill so I went +75 on the front and +100 on the rear.

Changed castor +1. And worked on alignment. .2/ .4 I figured positive on the rear to help push the car through the turn up the hill?

Am I on the right path or am I heading down a rabbit hole?
I sort of am but I know that it can be a puzzle , and I'm wondering if it was just and alignment issue. Or should I have been doing arbs?


I did a couple of laps with your tune, it turned in too slow for me, but i like my cars soft and loose with quicker turn-in.

Here's a quick tune, i only did a couple of test laps so it will probably need a bit of slight tweaking, i was running 1:52.xxx with no assists on Prague full.

Tuning:
Tires: 29/29
Gearing is stock (n/a)
Chamber f/r -1.7/-1.0
Toe (f/r) = 0.0/-0.2
Caster = 6.0
ARBs (f/r) = 15.02/15.06
Springs (f/r) = 390.0/390.1
Height (f/r) = 3.3 / 4.9
Rebound = 8.1 / 8.3
Bump = 2.5 / 2.0
Aero full = 122/ 337
Brake balance = 53%
Brake pressure = 105%
Diff accel = 40%
Diff decel = 10%

Mash Tuned since 2005 | Youtube






Rank: A-Class Racing License
#111 Posted : Tuesday, April 22, 2014 9:43:04 AM(UTC)
Thanks, Mashed... I gave the setting a go, I wasn't really a fan of it. It was a little soft for my liking. I was having trouble getting to the 152s and I could get 152s in the version above. I appreciate the tune but I was really looking for a what would you do:

You have tune that is good on tracks like the below
As base tunes go the one I have is pretty darned good. Under 250 in S class isn't bad (xbow, F50, acrX)
Leguna, Indy GP, Bathurst, Spa, LeMans (147) all ranked in the 200s or below.

So do I scrap the settings for Prague and I assume alps or is there a process to adapting the setting to the track?

What is the prefered method of tuners... Springs - ARBs - Dampening - Chamber - What order do you work on them and what increments do you use as you are changing settings ---


_____________________________________________________
*I got help from PTG guys:

I have since lowered--- took the original tune above - tried differing castor amounts until I like one (5.5) and then started dropping the spring rates (they are -100), reduce bumps by .5 ( for then because I wanted a little less understeer on throttle heading up the hill and the double left after the tunnel so I soften the front ARB - .3
Changed my Diff accel to 35%....

I'm #111 with a 1:50.273 (there's a sub 50 in there but I was really making it for a 30 lap race, so I'm trying for consistency and I don't want to get use barreling though the chicane and hitting the walls over and over and over,... So a full 2 seconds in suspension and castor.

Edited by user Friday, April 25, 2014 6:36:16 PM(UTC)  | Reason: Not specified

Rank: B-Class Racing License
#112 Posted : Friday, May 2, 2014 3:35:20 PM(UTC)
Can someone tell me what CDF refers to?

I see it in the description of tunes and in the titles of some of the open source tunes. I have been a motorsports fan for a long time but I can't figure out what CDF represents in a tune.

I found the answer. It stands for Championnat De France. The tunes and designs are from the French racing series.

Edited by user Monday, May 12, 2014 9:07:13 AM(UTC)  | Reason: Found the answer


Rank: Driver's Permit
#113 Posted : Sunday, June 22, 2014 12:30:25 PM(UTC)
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Rank: Driver's Permit
#114 Posted : Tuesday, June 24, 2014 3:45:18 PM(UTC)
This is great information thank you
Rank: Racing Permit
#115 Posted : Tuesday, June 24, 2014 9:13:45 PM(UTC)
Could someone give me some advice on tuning an AWD car? Particularly the R35 GTR? I like the stock tune, but it understeers in low speed corners and sweepers.
Rank: Driver's Permit
#116 Posted : Tuesday, July 8, 2014 4:58:04 PM(UTC)
Originally Posted by: BEACHEDAS25 Go to Quoted Post
Ok so advice in hand I made my first attempt at tuning a car. I tried a grip tune. I learnt a lot but it was a terrible first attempt haha. I thought it was pretty good cause I shaved some time off my lap times in test drives while playing with the settings but then went and raced it and I was a good 4 seconds slower than everyone else. Well I will be throwing that tune away haha. I think where I went wrong is my upgrade selections (well the tuning settings as well but first thing to sort out is getting the right upgrades). I choose racing tyres but then it severely limited me on other upgrades that I could add as it put me too close to the class limit. I then could not adjust the gearing, alignment, springs, damping and brakes I gather cause I didn't have the right upgrades (Is that correct?). Also adding Aero dropped the speed rating from 5.2 to 4.9 (not sure if Aero is needed on a D class either). In test drives though having the aero improved my lap times greatly over the stock rating so wasn't too bothered at the time until I really underperformed in an actual race with it.

The car I attempted to tune was the Toyota MR2 SC 1989. Stock its a D350. I wanted to tune it to D class. I added Race tyres, Racing rims which shaved off 25lb, increased rim size to 17 in and increased tyre width (I forget by how much I think it was the 1st selection after stock size cause I was too close to class limit). I added street springs and front and rear anti roll bars. Then added Aero front and rear, a supercharger(trying to compensate for loss of speed from Aero) and race differential. Stock it was S 5.2 H 4.3 A 6.1 L 6.8 B 4.2. After upgrades it was S 4.9 H 5.2 A 6.2 L 7.0 B 5.4. Lap time stock was 2:01.082 On Indy circuit. Lap time after upgrades was 1:51.463. Playing around with the settings I could adjust the lap time was 1:49.875. I think I ended on Tyres 28.5 psi (heat 230 F and psi was about 34 I think) anti roll F 26.24 R 18.26 Aero F 65 R 130 Diff A 90% D 75%. Any advice on what I should have done and should do to improve it would be greatly appreciated.

I've just downloaded the Forza droid app on my phone. Will this still work with Forza 5 and is it worth using?

Also by the way what is launch excuse my ignorance but not sure what it is?



In my experience, D class cars don't need aero at all even in a grip build. However, based on my knowledge, I always put a bumper and wing on either way and take out all the downforce, since I'm pretty sure that results in less overall downforce. I usually ignore the performance bars to a certain extent since I find them inaccurate concerning the aero upgrades (might be wrong on that?). Based on the starting point on that car I would recommend street tires at the most, but I would leave them stock, since D class in my experience doesn't require higher compounds. If you're going for a grip build I would recommend just widening the tires, instead of upgrading the compound itself. I would max out everything in the handling section on every car as default (race everything) except the chassis and the weight reduction, as that varies. Based on my experience, I usually lower the differential settings to around 35% and 15-8% front and rear on an RWD car, but I think that may be personal preference. I think part of your troubles is that Indy GP is a speed track, which may not have helped your times. Even though its a grip car, you might not have enough speed parts on it, and/or you might have a inaccurate gear ratio for that track. Hopefully this helped :)

Note - I'm a relatively new tuner, and some of this info might be wrong. If any experienced tuners could make sure I didn't mess anything up, I'd appreciate it. Also, could someone confirm that the bumper and wing actually provide less downforce on the car provided you move the slider all the way to speed? I might have messed up big time on that (I have it on all my cars :/).
Rank: Driver's Permit
#117 Posted : Tuesday, July 29, 2014 6:53:51 AM(UTC)
Simple question Worm. I notice when I'm going through a corner, my outside camber is very slow to change. Usually when I'm finally coming out of a corner the camber will move the closest to positive it will get. Does this mean my suspension is too stiff possibly?
Rank: On the Podium
#118 Posted : Tuesday, July 29, 2014 7:27:19 AM(UTC)
I don't really pay attention to the telemetry readings as I don't find them beneficial to tuning the car. A lot of times going by that will hurt more than it will help.

What is your camber?

Spring setting wise where is the number percentage wise with the furthest left being 0% and the furthest right being 100%. That will give me an idea of where the springs are.
Rank: Driver's Permit
#119 Posted : Sunday, August 3, 2014 4:09:57 AM(UTC)
Originally Posted by: TG Wormburner Go to Quoted Post
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 32-35 degrees 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.

Easier explanation on braking can be found HERE courtesy of gtFOOTw. Have a look. http://forums.forzamotorsport.n...PLAINED.aspx#post_126446



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.

There isn't a ton I can find on differential settings so sorry for being so brief here and it is pretty simple. A higher number creates oversteer and a lower number prevents it.


Rank: Driver's Permit
#120 Posted : Sunday, August 3, 2014 4:15:13 AM(UTC)
that is awesome dude you must be a race ace mechanic sure you are not lewis hamilton. so much detail cannot get my head round all that info, keep up the good work in trying to educate people like me .
Rank: Driver's Permit
#121 Posted : Wednesday, August 20, 2014 10:08:51 PM(UTC)
Well I learned something today

Edited by user Wednesday, August 20, 2014 10:42:09 PM(UTC)  | Reason: Not specified

Rank: Driver's Permit
#122 Posted : Monday, September 8, 2014 3:22:57 AM(UTC)
Just remember this is a basic starting place as every car will respond differently AND no two drivers are the same. You must tune every car to your driving style.
Rank: Driver's Permit
#123 Posted : Saturday, November 1, 2014 2:15:05 PM(UTC)
Originally Posted by: IchII3D Go to Quoted Post


  • AERO -... Your modern Ferrari, Zonda, Lambo etc... really don't need a front splitter and often not even a rear spoiler. Remember this very much depends on the track. Aero does help with braking and acceleration grip, but your car can very easily feel to heavy and sluggish when you simply might not need it with better mechanical grip setup. Good examples of not needing Aero are the Ford GT and F50. .


  • Sorry, this is IMHO the opposite. As well in real races like in Forza 5. Every F50 I saw in the Top 10 leaderboards had a rear wing and especially this cars suck without. Yes, they "feel" different, like you have to much luggage in the trunk, but handling is so much better and the lap times as well. The downforce is the main setting to compensate the low handling rates this cars have compare to cars like the KTM-X-Bow. In real races it's the same. Higher classes have always rear wings. In low classes it's not allowed or not necessary, but in Forza it seems always be a wise choice.
    Rank: B-Class Racing License
    #124 Posted : Monday, November 10, 2014 9:35:33 AM(UTC)
    Thanks for the info
    Rank: Driver's Permit
    #125 Posted : Sunday, November 23, 2014 9:44:47 AM(UTC)
    there is a tune for a 90,camaro iroc z i found one for 289mph and i cant get it cause my file is corrupted if you know the numbers of the tune please reply back to me thanks
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