Rank: Racing Permit
#1 Posted : Saturday, October 4, 2014 4:42:34 PM(UTC)
Okay, so let me start off by saying that I have been playing racing games for a long time, but have never really understood anything besides basic upgrading. I know none of the math. But FH2 has gotten me thinkning about tuning, and after reading a bunch on here about how to make a good grip tune, I have a few questions about my 1997 BMW M3. It is the first car I am heavily tuning to make my own, and I think I have a good start.

Can someone give me some pointers on what to change to help certain things? Just some advice on what can help me make a good grip tune on this car. Thank you, and I am absolutely loving the game.

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Rank: Driver's Permit
#2 Posted : Saturday, October 4, 2014 5:46:11 PM(UTC)
Same here i can't find any good tuts :(
Rank: D-Class Racing License
#3 Posted : Sunday, October 5, 2014 12:02:36 AM(UTC)
Its all trial and error really just look up past motorsport tutorials for forza
A
Rank: C-Class Racing License
#4 Posted : Sunday, October 5, 2014 1:10:39 PM(UTC)
Its a difficult question to answer. One size does not fit all. Do you like grip or do you prefer power? Im a grip kinda guy. Tires and weight reduction before engine mods.
Also, what works in forza does not always work in horizon. Race suspension just doesnt work on city streets and dirt roads.

Edited by user Sunday, October 5, 2014 3:31:12 PM(UTC)  | Reason: Not specified

Rank: A-Class Racing License
#5 Posted : Tuesday, October 7, 2014 4:54:37 AM(UTC)
There are some wonderful tuning guides on the FM5 tuning lounge forums. I'm not sure how much the game takes dirt into consideration with the different upgrades added. Surely a car with race tires would not handle good on dirt, but I don't think the game accounts for that. I'm no tuner at all but there are a few things I do know, typically on your telemetry shoot for 32-33.5 psi on your tires at race temp. Diff settings typically go way lower than stock. The tune really depends on the build when you're trying to get the most out of it. Take for example adding adjustable aero creates downforce which creates more load on the springs. Some settings are co-dependant whereas others are stand alone. If you really want the best knowledge available I suggest the FM5 tuning lounge guides.
Rank: Driver's License
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#6 Posted : Wednesday, October 8, 2014 10:03:12 AM(UTC)
The text accompanying the tuning parameters provides a ton of helpful informationbut can be a bit daunting in that it doesn't really guide you you in how or where to start. It's more like crib notes where you know basically what you're doing but just need a reminder of some specifics.

That said, my approach to tuning in this is essentially the same as previous forza games:

Decide on spring constants. I use the simple calculation of (vehicle weight) * (weight bias) / 2. For instance, a 2000 lb car with 60% of its weight in front would start at 2000*0.6/2 = 600 lb/in in front and 2000*(1-0.6)/2 = 400 lb/in the rear. This would mean that the curb weight alone will compress the suspension 1 inch and should limit overall swing to 3-4 inches or less. This is great for a smooth course but can be completely unusable off-road. But because it's based on the car's weight balance, it should be fairly neutral as long as the tire widths aren't very different. For fatter rear tires, you'll want to use a stiffer rear suspension. In Horizon in general, I would drop all the spring values 20-50% from these initial rates and raise the ride height to allow for travel.

Next, I set sway bars to the minimum. They won't stay there. This is only temporary to adjust the shocks. Shocks complement the springs. Without shocks, springs bounce. But where springs provide a force in oppositition to displacement, shocks provide a force in opposition to rate of change. That is, if you squeeze a spring to the same level of compression quickly or slowly, it will push back with the same force. But if you squeeze a shock slowly, it will eventually fully compress and if you punch it hard it might not compress at all. Another way to look at it is that springs store energy while shocks dissipate it. Properly tuned shocks dissipate the energy that would otherwise lead to oscillation in the spring.

Shocks offer two adjustments: bound (sometimes called bump or jounce) and rebound (usually called rebound). These settings control how rapidly the suspension can transfer weight in response to road conditions and driver input. Bump is the compression rate and rebound is the extension rate rate. Bump controls how quickly the wheel can be pushed up into the wheel well and rebound controls how quickly (and forcefully) the spring can push it back down into the road. Since bump is acting against the monentum of the whole car (imagine reaching the bottom of a hill or entering loop-de-loop stunt) it will have to be stronger than the rebound, which is acting only against the unsprung wheel/suspension parts. They'll also have to be balanced against the combination of spring stiffness and suspension travel you want. For the initial spring rates above, starting at about 8-9 in front bump is reasonable, with the front rebound about 20% lower, and the rear parts related to the fronts through the weight bias similarly to the springs.

Alignment needs to be set with telemetry. It starts with caster. Caster is analogous to rake on a motorcycle. The reason it is important and should come first is that it makes camber more negatative as the wheel is turned from center to lock. With a good caster setting, the wheels can be almost straight up when car isn't turning but tilt enough to keep the contact patch level through a turn. The real-world penalty is stiffer steering but I don't think this is modeled in Forza. A little negative camber can be a good thing. It can make up up for what caster might not be able to accomplish alone as well as providing a little extra straight line stability. What you need look for is that the tire is heating evenly across its contact patch. You should aim for a difference of 0-5 deg F warmer on the inner edge than the outter edge

Usually, if your caster is good, you won't need much more than about a half or maybe a whole degree negative in the front. On rear wheel drive cars, it is rare to need more than about half your front camber setting on the rear axle. I usually set it to about -0.6 front and -0.3 rear. This is generally reasonable for FR and AWD cars but will need to be adjusted to keep tire temps in line. FF can deal well with ridiculously negative rear camber. MR and RR, I'll admit I don't know well but would try to extrapolate from FR.

Toe is pointing the wheels toward or away from each other and generally shouldn't be needed except for very fine tuning. Toe in can improve straight line stability but decrease a car's turn-in ability. Toe out can improve turn-in to the point the can feel like it "wants to turn" even if its driver doesn't. Some recommend a little front toe out but my own belief is that it's better to get the handling situated by spring/damper/sway bar settings. That is, the suspension is the core of the handling while the alignment refines it slightly, kind of like course/fine knobs. Real world cars generally have slight front toe in to feel stable at highway speeds and because typical drivers are safer dealing with understeer in a panic situation than they are with oversteer. Also, toe-in warms the outer edge of the tire and toe-out warms the inner edge.

This would be enough for a (probably hairy) first test ride. You'll want to note the car's characteristics entering corners, apexing, and exiting corners. Telemetry data would tell us what to do with the tire pressure and alignment. The goal is to keep each tire's cross section evenly heated, to keep all 4 tires at similar temperatures, and for those temperatures to be in the 180-210 F sweet spot for traction. Camber, caster, and toe will all affect the tire temps one edge of the tire while pressure will affect the whole tire cross-section. More pressure generally mean cooler contact patch. At extremes, low pressure will cause both edges to warm and the center to cool while high pressure will cause the center to warm while both edges cool (think of the tire as a balloon and it should make sense why).

Next, we can set about refining the suspension we crudely pieced together above. If the car is completely unmanageable off road, it will need softening all around and possibly increased ride height. The corner entrance characteristics are most affected by front bump and rear rebound (think about what each of those reflects and how a car behaves under braking and it should be clear why). Apex performance is mostly dictated by sway bars. Corner exits are mostly dictated by front rebound and rear bump. Spring rates affect all aspects. For this part, think of understeer as a loss of front traction and oversteer as a loss of rear traction. The parts above can be softened to increase an axle's traction or stiffened to decrease it . And we're talking relatively, so stiffening the front is similar to softening the rear. If the overall suspension is too stiff (or ride height too low), you might have very sudden snappy, fishtailing problems. If it's too soft, it'll feel unresponsive (understeer tuning can also make a car feel unresponsive even if the suspension is otherwise alright).

Braking usually isn't worth adjusting. Generally biasing forward causes understeer under heavy braking (binds front wheels) and oversteer with rear bias (binds rears). With telemetry, it can be tuned to lock all wheels together (which maximizes braking efficiency).

Differentials can be tricky but are straightforward. On AWD, setting the center diff controls how much the car acts like FWD or RWD, and is usually set to 60-80% rear on most real world cars (more FWD translates to understeer and getting beyond about 85% rear just begs the question of why not just go RWD full time). On actual FWD or RWD, you use accel to try to maximize traction on the drive axle during throttle-on. You'll know you have enough when burnouts stop leaving a single skidmark. You might have too much if the drive axle loses traction on throttle through corner (this also happens by applying too much throttle). Decel setting can alter a car's balance under braking or just lift-throttle conditions. The default settings for both tend be a bit higher than necessary.

Oh, and I almost forgot gearing. It's easy. Tweak the final drive until you find the best top speed. This will set both the final drive and top gear ratio. Then, fiddle with first (and maybe second) to optimize 0-60 time. Then space the gears somewhat evenly, with the higher gears maybe a little closer together. Take note of the peak torque and power of your engine and verify that you're remaining in a desirable rev window with a test drive.

Anyway, that's the basics. I'm sure errors and omissions will be pointed out. This isn't meant as the be-all end-all but rather a primer and a jumping point for discussion of theory.

Edited by user Thursday, October 9, 2014 2:42:16 PM(UTC)  | Reason: Not specified

Rank: D-Class Racing License
#7 Posted : Wednesday, October 8, 2014 10:43:40 AM(UTC)
As others have pointed out, there is a wealth of resources buried in the FM5 and FM4 forums... ExaltedDuck laid the basics out pretty well too, so I'm not going to post a long drawn-out intro.... I will point you to a pretty good read online. It should help you further your understanding of tuning....

http://www.rapid-racer.com/suspension-tuning.php

Cheers!
Rank: Driver's License
#8 Posted : Wednesday, October 8, 2014 11:12:19 AM(UTC)
And for those who just need a little help you can use a tuning calculator. I used them all the time in previous Forza games. They are not an end all be all, but they can put you at a great starting point where you can mess with little things from what it gives you to get a pretty good tune going:
http://forzatuninglabs.com/about.php

There is also a phone app called ForzaTune one both iPhone and Android.

Rank: Driver's License
#9 Posted : Thursday, October 9, 2014 9:20:44 AM(UTC)
Just wanted to drop a reply to say I edited the above post. I was wrong about the telemetry mode. Apparently there is one but I missed it. So I edited out my bitter references to its absence and fixed a few typos while I was at it.
Rank: Racing Permit
#10 Posted : Thursday, October 9, 2014 1:09:56 PM(UTC)
Originally Posted by: ExaltedDuck Go to Quoted Post
Just wanted to drop a reply to say I edited the above post. I was wrong about the telemetry mode. Apparently there is one but I missed it. So I edited out my bitter references to its absence and fixed a few typos while I was at it.


Wanted to say thanks - big thanks. I don't know how much time it took to write, but that intro was a *great* post. Easily among the best of the many I've read on the subject.

It's strange how the same topics can be discussed in so many different ways, yet some of those ways can make those same topics so much more approachable. I'm big on analogies and explanations that paint pictures in my mind. You have a lot of talent when it comes to painting those pictures. I could "see" and "feel" what you were describing.

This was also very generous of you. It can be disheartening to see the negative posts on this board, but then you see one like this and it reminds you how amazing the community can be.

And if we see a pinned tutorials thread around here, I think your post should absolutely be included. I've clipped it and saved it to Evernote so that I'll never lose it, no matter how buried in other threads it might become.

Really. It's awesome that you put in that much effort to help us out. Very, very cool. Thank you.

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