The below tuning was written with Forza 2 in mind but the priciples are the same in real life and therefore, apply to Forza 3 as well. Edit: EpicZ

Here's some car tuning tips that I found on the internet.

Forza Motorsport 2 - Tuning Section
In Forza Motorsport 2, driving the car is only half the fun. Once you've driven around all the tracks, you'll notice that some of the computer-controlled cars are just so much faster...time to take advantage of Forzas awesome tuning section.
There are so many tuning adjustments in Forza Motorsport 2 that it can take some time to find that 'perfect' setup. Below we list all of the tuning options and tips on adjusting to benefit your car.

Anti-Roll Bar
The purpose of an anti-roll bar is to control body roll through a corner. A thicker bar equates to less body roll, a thinner bar is more body roll. In general, a thicker bar will make a car more agile, more sensitive to steering inputs. A thinner bar will make a car more lazy, a little more forgiving.

Anti-Roll Bar, Front:
A stiffer bar may take away steering entering a corner, but provide a little better exit steering. Start soft.

Anti-Roll Bar, Rear:
• On the rear, a stiffer bar will allow the car to rotate through the corners better and should square the car up out of the corner. A softer bar will lock the rear end in, even resulting in under steer out of a corner. Start soft.
Use the Anti-Roll Bars as a fine-tuning adjustment instead of a 'crutch' for an ill-handling car.

Camber:
Camber is the inward or outward vertical tilt of the top of the tire. Negative camber is the tilt of the top of the tire towards the center of the vehicle (used often); positive camber is the tilt of the top of the tire away from the center of the vehicle (used VERY rarely). Proper camber adjustments are very critical for achieving maximum cornering speeds.

Camber, Front
• FWD cars: Because a FWD car uses the front wheels for steering and acceleration, camber adjustments must be made in VERY small increments. Start with -.5 to -.7 degrees of camber. Remember, to much camber will affect straight line acceleration.

• 4WD cars: Because of the additional drive to the rear wheels, you can be a little more aggressive with your camber settings than a FWD car. Start with -1 to -1.2 degrees camber. Note: if you have to much front camber you will overheat the front tires. This will cause your car to push more in the corners.

• RWD cars: You can be much more aggressive with your front camber adjustments on a RWD car. Start with -1 to -1.5 degrees.
Be careful not to set your camber to aggressively (above 3 degrees). This will cause the outside tire (in a turn) to roll past the contact patch, reducing steering. You can pull up your Tire Wear Indicator to see how your camber is affecting your tires (green is good, red is bad). If you see red, reduce the front camber setting.

Camber, Rear
• FWD cars: On a FWD car, the rear wheels are only along for the ride. You can start with the rear camber at -.2 to -.5. Depending on the class you are running, you will need to adjust the camber to either free up the car (less negative camber) or lock it in (more negative camber).

• 4WD cars: Less rear camber will allow a 4WD car rotate through corners better. It will also allow a 4WD car to hook up out of a corner, resulting in better acceleration. Less rear camber will also allow you to run more front camber. Start with -.1 to -.5 rear camber.

• RWD cars: Be conservative. There is a fine line when setting rear camber. More rear camber will negatively affect acceleration & braking, but lock it in the corners.

Differential
The differential is a gear assembly located at the rear of the car. It's purpose is to distribute torque to the rear wheels under acceleration.
In some games, you are allowed to change the differential gears, allowing different ratios for different size tracks. In other games, you are only allowed to adjust when the diff 'locks' in either acceleration or deceleration. We'll discuss both briefly.

Gear Adjustment:
• If you can adjust the F.D. (Final Drive) of the differential, remember these key notes:
1. Higher number (ie, 5.5) equals a smaller ratio, or quicker acceleration. This also means, however, less top speed and, in some cases, lower fuel mileage. Used mostly for short tracks or tracks with a lot of low speed turns.
2. Smaller number (ie, 2.5) equals a taller ratio, or higher top speed. This also means slower acceleration. Used on tracks with long straights (or ovals).

Limited Slip Adjustment:
• As mentioned before, some games (like Forza Motorsports), allow you to adjust when the rear (or front) differential 'locks'. This creates a posi-traction rear end. Posi-traction rear ends are designed to provide traction when one wheel has more traction than the other. This is what is adjustable…how much wheelspin is needed before the differential 'locks'.

Acceleration, Front: (FWD/4WD)
• Increase this setting to increase under steer, decrease to reduce under steer.

Acceleration Rear: (FWD/4WD/RWD)
• Increase this setting to increase oversteer, decrease to reduce oversteer.

Deceleration Rear: (4WD/RWD)
• Increase this setting to reduce off-throttle oversteer, for instance, entering a corner. Decrease this setting to increase off-throttle oversteer. Set correctly, this setting will help a car rotate though the corner with a small amount of drift.
Center Differential Adjustment:

• Most 4WD car come with a center differential adjustment. When a 4WD car accelerates, weight is shifted to the rear wheels (especially high-powered vehicles). That lightens the load on the front, causing the front wheels to spin, wasting power. The center differential adjustment adjusts the power transfer between the front and rear drive wheels.

Shocks
Shocks are designed to control the suspensions up (bound, or compression) and down (rebound, or droop) movement caused by bumps in the road. They also play a major roll in controlling how quickly weight transfers during acceleration and braking. In general, the stiffer the shock, the less grip that end of the car will have in the corners.

Understanding Bound/Compression and Rebound/Droop is very important to tuning shocks. Basically, Bound/Compression is pushing the shaft into the shock (making it shorter), and Rebound/Droop is pulling the shaft out (making it longer). On the track, when you accelerate, the front of the car raises (rebound) and the rear squats (bound). When you brake, the front dives (bound) and the rear raises (rebound). Now, tuning that to win is another story.

Front:
• More front bound will result in more weight transfer, which will allow the front to dive more into a corner. Remember, too soft will cause the car to bottom out.

• Less front bound will prevent the front from diving quickly, which will reduce steering into a corner.

• More front rebound will help keep the front tires in contact with the ground under acceleration, resulting in better on-power steering.

• Less front rebound will lighten the front end under acceleration, causing a car to under steer out of corners. This may also make a car unstable during acceleration.

Rear:
• More rear bound will result in more weight transfer, which will allow the rear to squat under acceleration. This may cause the car to under steer exiting corners. This will help, however, in straight line acceleration.

• Less rear bound will result in a stiffer rear shock and can cause the car to be unstable under power.

• More rear rebound will help lock the rear end in under braking, possibly to the point of slight under steer.

• Less rear rebound will help the car to rotate in the corners, but at the cost of stability.

Tire Pressure
In all racing, tires are about 80% of a car's setup. The wrong tire can negate an entire setup. In fact, all the setup changes you make to a car are to benefit the tires you are using.

Tire pressure is simply how much air you have in a tire. The hotter a tire gets, the more pressure that tire will have. You can use this to help set your cold-tire pressure. If you know that your tires work best at 30psi, you might set the cold-tire pressure at 25psi. Experimentation here is key.
Tires with to much pressure can become over-inflated. Tires with to little pressure can become under-inflated.

Front:
• Over-inflated tires can cause a lack of grip and induce under steer. They will, however, run cooler, have less drag and allow higher speeds.

• Under-inflated tires will give better grip, but can also result in excessive heat in that tire, causing more wear. They can also reduce speeds to the excess drag.
Also note that lowering the tire pressure also lowers the overall ride height of the car.

Transmission Ratio
The transmission is designed to change transfer engine power to the wheels through a series of gears. Most cars have either an automatic or manual (stick) transmission, and have between 4 and 6 gears (for this discussion, we'll use 6 as our number). In most games, you have not only adjust the ratio of all 6 gears, but the Final Drive (F.D.) ratio also.

Final Drive (F.D.):
• The F.D. can be adjusted to scale up (or down) all 6 gears together as a group. All together, you can tune your transmission for acceleration or top speed. The lower the F.D. number (ie, 2.50), the less torque but more top speed, good for tracks with long straights or ovals. The higher the F.D. number (ie, 6.50), the more torque, but less top speed. Use this for tight, winding tracks.

Gears, 1st - 6th:
• As well as the F.D., you can fine tune your gearing though the individual gears. For tighter tracks, you might lower the F.D. ratio (remember, higher number) for more torque, but up the 4th, 5th or 6th individual gear to get a little more top end. For longer tracks, you might raise the F.D. ratio (lower number) for more top end, but lower the 1st, 2nd or 3rd individual gear to get a little more rip out of the slower corners. This is trial and error.

One more thing on Gearing. Your F.D. and individual gear setting will depend on the power you car has. If it is a lower-powered car, tuning for more speed will significantly hurt your bottom end. It may also not be able to hit the speeds you want because the motor doesn't have the power (or torque) to pull it through the gears. Gearing on lower-powered cars is a lot more crucial than higher-powered vehicles.

Again, awsome advise and education Tom!

Thanks i need to learn how to tune a car properly. This should help me lots.

Im not so sure the shock function is correctly explained here.

My understanding is that the value represented in the tune settings of FM3 is the shock's resistance. Low Bump means that weight will transfer FASTER to that shock. Low Rebound means that weight will transfer FASTER away from that shock. The amount of weight is dependent on spring rate.

Maybe Im completely wrong, but a lower front bump will result in more front squat, not less like the above says.

Ive typically got the following article beside me when tuning. It breaks everything down into different phases and explains how to fix that stage, and what other stages that adjustment also effects. This is real world stuff.
http://www.smithees-racetech.com.au/theory/shocktune1.html

If anyone disagrees, Id love to hear it. I was recently corrected to the thinking I have now and things seem to make much more sense when tuning shocks now.

Very nice TomCat7 :-)

So, I'm a tad confused. You say increasing the bound or rebound works the exact opposite of how it works in real cars? Normally a higher setting for bound will make the dampener stiffer. So less weight transfer. And this seems to be the case in FM3. Rebound, normally a higher setting mean stiffer resulting in slower expansion and weight lifting off the tires more slowly. Again, that is what I have noticed in FM3 as well.

Camber I'm also a bit miffed by. I tune camber just like I do on my real car. Temp inside to out. I want about a 10-15 degree F spread from edge to edge if possible. I've been doing this in FM3 and it works great. Even wear in long races and more consistent cornering. Granted you can not always do this. Especially with very powerful cars. Some times the added camber will cost to much straight line traction. I have noticed camber is way less than real life. Figure my Hoosier A6 slicks I use for autox recommend a front camber of -3 to -4 degrees on front drive cars. The R6 track slicks drop to -2.5 to -3.5. A race car out side of P1-P2 it's almost unheard of to have -1 or less camber. The only reason the really high level ones don't need it in real life is because of all the down force. As far as FM3 goes, I have noticed most cars vary from track to track but I can run any where from -.8 to -1.8 with only a few breaking out of that. My main goal with camber is keep the temps in check. Then adjust suspension to control the car. Camber is meant to maximize the contact patch in corners. As long as you keep the tires in the 10-15 degree sweet spot, you know you are using all of the tire.

I'm no master tuner, but that's what I do in a nut shell. But I base this off real world practice and learning. And on PC sims since they seem to be more like real life.

On the plus side, FM3 uses a "fake" generic suspension model for all cars so you don't have to adjust your tuning for varied suspension style and axles. All cars use full independent suspensions and have the exact same camber curve. Makes tuning a bit jacked up for some cars, like Golfs and classics with solid axles.

I'm not trying to call you out or anything. Just noticing things that are not exactly the same from what I have seen to what you posted. Most everything looks good to me, but the dampeners and camber are very different from my experience. And camber is very different from real cars.

I agree with all points you posted Prophet. Im not really sure some of the info Tom posted is accurate either. Especially the shock function.

Oh, couple more things I did not think about before.

On AWD and front drive cars, mostly front drive, bumping decel on the front diff you will minimize off throttle oversteer. Works very well for getting squirly front drives under control. Or for high speed off trhottle turns like the long right hand sweeper on Iberian.

Also for tires, the sweet spot for pressure seems to be 31-32 psi hot. So after 4-5 laps the tires should be up to temp and in most cases you want to try and keep pressure at around 31-32 psi in the telemitry screen. This can be tweaked for feel. But in genral that seems to work best. Supposedly the tire just below the race tire works best at around 42psi, but I'm not sure that is true. I don't use them much but that seems high. I only use pressures like that for Autox. Not track use.

After reading the part about bound and re-bound, it dosn't make too much sence.

This info was for Forza 2 and I will try to find where I got it from. lol

LOL, yeah, this is oiver a year old. Maybe we should lock it, and update it with the new FM3 info............

I can help the main tuners here come up with a guide.

I think the main problem here is that it is hard to come to an agreement on what works and what doesnt in game. Its easy to sit back and apply realworld info (I autoX as well, with limited tuning options..). But I dont really think 100% of real world info applies.

There is the IFCA guide that covers alot of stuff, but that same issue remains. It really seems like some real world stuff is overlooked. I wonder if its because it was written for what the game wants, not real life.

Any help ANYONE is willing to give for tuning is more than appreciated.

Prophet, we really dont have a main tuner. We sort of all just help out each other. There were some guys that held that title, but they are no longer with us.

Well, in taht case, I can toss my two cents in when needed.

I will go as far as to say the physical simulation of suspensions and tires is a total joke compared to real good PC sims like Live For Speed, rFactor, or the SIM BIN family. They do a really good job faking that feel, but because the cars do not tune like real cars it shows how off the modle really is. Not that the PC sims are perfect. Just better. Forza is fun but really not a true sim. I'm not sure if it's system limitaions or lazy programmers, or just Microsoft putting impossible dead lines in forcing them to make short cuts. I'm pretty usre the reason the modle is funk is the same reason things like active aero parts don't exist and things like 3D models for brakes not changing with upgrades like FM2. I think it all ties togethor in a round about way.

Fun game, janky modling.

Thanks for the offer.

I agree that things dont make sense sometimes because the physics/suspension model isnt quite right. And it doesnt help when you try to mix the real info in with the FM3 info.

Rez, we can certainly do something with this thread. The problem is...what info do we put in here to make it more accurate? I know I certainly dont understand it all enough to put it on paper or post it. And my consistency (or lack thereof) doesnt help me to figure out what really works and what doesnt.

I was thinking about deleting my entry and finding something that is closer to Forza 3 Tuning.

I think more tuning logic rather than settings. Regardless of how you set up a car, all the parts will do the same thing for every one. It's more of how you use them. Srings are springs, dampeners are dampeners. We may go about how we use the tools in differnet ways but in the end making something stiffer will do the same thing for every one.

Different tunes also work for different styles too. Stock Car is a perfect example. Chuck, Tom and myself all tune our Stock Cars pretty good for ourselves. When we go to share them, they are all VERY different from each other.

stock cars are sort of a whole different animal. But the same does hold true with some of the "normal" cars. Ive been adapting to Epic's tunes and he's been adapting to mine. We've sort of met in the middle. And when he sends me a tune, I adjust brake pressure and test drive. And most of the time, alot our settings are really close to each other.

We will probably lock down this thread. No need to delete anything.

We can archive it. Just say the word or use the the control at the bottom left of the page if you are an admin user.

here's a link Ive refered to a time or 2. written for the nissan se-r, but some good info in between all the autox and se-r stuff.

http://www.se-r.net/car_info/suspension_tuning.html