Car build DO's and DONT'S?

I approach all of my builds in the following order...

1-suspension, ARB's, brakes, roll cage, transmission, & Diff

2-weight reduction

3-tire compound , width, & rims (including rim size

4-aero

5 motor last

It seems that Forza 4 really likes a grip build more than anything in most cases. The exception to this rule being Lemans & the Nordschleiffe. Grip & acceleration are hat you want to shoot for.

As for the motor part of things, I always use forced induction of some sort of possible before adding other engine upgrades.

Clutches, flywheels, & drive shafts are pretty useless except to get a couple of extra points when nothing else will fit.

Feel free to hit me up if you have more questions or would like to get a few of my tunes to see how I go about diong things.

lift throttle oversteer I'd go with stiffening the decel setting on the differential.

After taking JCotter's 427 Cobra for a spin (A class) I loved how easily it rotated and started trying to make my Corvette GS behave similarly. The biggest change came from dropping the decel on the diff from 60 down to 20, then back to 25 because 20 was a bit too squirrely under braking corner entry situations. Stiffening would have the opposite effect I would think. If you're already fairly stiff there/don't have racing differential, you can try slowing down the weight transfer some by messing with your dampers. Stiffer rear rebound/Stiffer front bump might yield what you're seeking.

I'm still pretty new to the tuning game though, so take my advice with a grain of salt. Follow whatever they say pretty much. Then muck with it anyway to try to prove them wrong. 

Like Voodoo said, bumping the decel setting up a little bit should help with the lift off oversteer.  Another thing to watch out for is some cars have a tendency to spin when downshifting into second gear, and as far as I know the only remedy is to put in a race trans and put in a longer second gear.

What track do you tune for to get a general lobby build?  

I'm using Suzuka West currently, just because I think that it has the best variety of turns (highspeed sweepers, some tight 90's, and a hairpin), has a decently long straight, and is a fairly short track so that I can turn a bunch of laps quickly.  If I need to tune the trans for a specific track, then obviously I'll run that track, take note of my top speed and tune it towards that.

Are there times when you shouldn't equip an aero package?

Generally the Aero is not a bad thing to put on in this game unless at a track that you need a speed build (Lemans, Nurburg, Sebring), but then again Forza aero looks like shit, so I tend to stay away from using it unless I really need to build a bonkers grip car (like pretty much all of my Lotus')

Do you select wheels for looks or performance? 

A little from column A, a little from column B

How do you go about selecting tire width and diameter?

I almost always try to put as much rubber on as I can ( is there a joke in there?)...

Are there times to use "lesser" roll cages?

Usually I slap the full race cage in, just because the P.I. hit is generally very small, but if you're in a pinch to get your car into a certain class you can probably do without.  I always put it into my classic cars though, without exception

Should I place a priority on vehicle weight or horsepower?

The game seems to reward faster accelerating cars over top speed cars, so generally you want to shed weight first.  

Are there certain upgrades to avoid altogether?

Like Cotter said, Clutch, flywheel, driveshaft are useless and should only be used to get an extra PI point or two to get you to the top of the class

Cotter's heirarchy is pretty close to how I build my cars, only I switch 2 and 3 around, but maybe that's why he's faster than me

I'd agree that 2 & 3 on my list are interchangeable. It just depends on the car. If ut's already supr light, go with tires first. If it's super heavey, go for weight reduction 1st. Or try a blend of the 2.

Like cotter said FM4 LOVES grip tunes! minus the ring and lemans i havent found a track a full blown grip tune doesnt compete on

I can usualy be found in d-b class i just started dabbling in the higher classes of late

For me after F class its

Race tires

Suspension, brakes, arbs, roll cage only in fwd cars up to B class than ill add it to rwd for a and up.. I find in some the weight hurts and makes my ass skip

Race reduction

forza areo set the areo to almost zero (sometimes ill do no areo tunes on grippy mid engine cars just cause there already glued to the ground)

the shitty super charger intake...i dont use turbo

If i still have a small amount of pi left ill add some tire width rwd cars i try ti use +1 size width on the back than the front and on fwd cars i use +1 rim size on the rear

basically i add all the handling components that i can within a class.....the key to all this is finding a light weight car with with good accel and decent power and your good to go....the hard part is forza 4 tuning specs are garbage ive built cars with awesome in class stats but run 2 secs slower than lower stat cars?   Iam gonna stop pretending that i know how to tune or know what iam doing.....heres my secret to my best tunes.....grippy light weight cars a really good 0-100 benchmark than give it to an alien to drive lol

AWD - not much experience tuning them for me outside of Drag racing, but  TrackAssassin has good suggestions about default differential settings [read here] that I tried that worked well as a starting point (and ending point mostly but again, I don't do AWD much - RWD swap baby!)... His suggestions are much better than the defaults IMO. I also tend to want to start the bias at 70% to the Rear.

For everything else, depending on how much PI you have to play with, go grip:

I go full on for tires with race compound, race width and set 17" for cars that are smaller and leave cars with 17" or higher alone) - if not enough PI, juggle the three to get teh best lateral Gs

Wheel - lightest possible to start - will return later and add weight if I pop over target PI. And don't forget that if you change from an upgraded wheel back to stock after you load it with different width, the width will be lost (compund too???) and needs to be added on again! I frequently forget that and cram in HP with all the new found PI. D'oh! 

Full aero (just to get the lat G's - i will tune them all down if it still drives well)

trans - depends but normally at least sport and race if it's a track specific tune since it's better to tweak the gears for each track individually)

diff - race always

save clutch and driveline for PI/weight shaving later

race brakes, arbs, springs, and weight if possible 

roll cage normally race but I have a ton of builds i didnt do anything on in order to keep weight down provided I am happy with the later Gs as is.

once all that is in, then check driveline and shave weight 

check PI - Have PI left? Now go to power... supercharger if available if not, try some forced injection if not, then:

For engine bits, I go for two things first and foremost - what gives most HP with most weight loss and most Acceleration benefit. Accel at this point since you built a grip tune is so important to finalizing that build.

Last chance to check if you can drop weight with driveline, clutch, hood or flywheel so never forget to check. Don't leave any PI or weight on the table and if you aren't on the lightest wheels already, go see if you can go lighter!

That's how I approach things. Not saying its right or wrong or good or bad... It's just what I do. Most tunes I put out are based off that concept. The tunes might change, but the base builds are very important. It's what separates one Leaderboard Spark to another. It's so very rarely soley the tune that is magic. 

Anyway..........

Don't bother with AWD cars unless you're planning on doing a RWD swap. Otherwise, they're completely useless.

You might be surprised with what can be done with AWD cars Cotter.  None will be competitive on the Ring or LeMans, but you can make a decent one that can put down respectable times at most other tracks.  Check out the Toyota MR-S AWD C class car that I put together for Kochino.  I was laying down times at Infineon and a few other tracks that were around 500th on the LB (which is about as good as I can do in any car).  I've put quite a few AWD's together now, and their biggest downside is that the power/weight is considerably less than the RWD's, so generally the top speed is way less but this is offset a bit by being able to get onto the loud pedal much earlier in the corner than you can with the RWD's, you just have to use an extra wide corner entry to combat the initial power on understeer.

Now that being said, yes RWD is generally >AWD, but they can still be fun to tune and drive....in the right circumstances. 

Steeler,

Def use Assasins guide to AWD if you want to build one.  It was like magic just making the changes to the differential.  I now pre-tune all of my AWD's to 25/0, 40/0, and 60 or 65%.  Then from there if the car gets snap oversteer when you let off the gas in the corners, start raising the decel on the rear by 5% at a time until it stops being a bastard.  Everything else is just tuned like normal with your springs, arb's and dampers to control your normal car balance.  

What we need to do is have an AWD night. That way we could get some use out of them.

But I digress. Back on topic now. :)

I up for that any time.  The question is which one of you fuckers is coming in second? 

I highly recommand running the pro-am series on Thursday night, or El Kochino's Tuesday night races. The faster/more experienced drivers are handicapped, thus making for a more competitive field as well as giving the novice drivers a chance to actually keep up with & learn from the faster folks.

I second that as well Cotter.  Both of those series are a ton of fun and highly competetive for all skill levels.  

Try not to get too discouraged though Steeler.  Some of us have spent rediculous amounts of time (years and years) trying to get good at Forza, and 2O4F has a large amount of what I consider to be very fast racers, and even a bunch of aliens as well.  And while I haven't raced much with you, from what I saw last night in garry's lobby, you are right there.  I'm not much of an instructor, but Cotter might be able to help you master trail braking, which will no doubt cut your laptimes compared to just "coasting" through the corners, as you put it.

If  you're interested in breaking free from the tuning calc's, let me know and we can set up a session where I can run down how I go about getting my initial settings, and how I tweak everything after that.  It's really hard for me to explain by typing, so it'd be easier to do through party chat, if you're interested.  Also, check out this website: http://diy-racetuning.net .  I've found that site extremely good at explaining what settings do what to which component.

That was me singing your praises Sarcasmo. You're welcome :)

Honestly though. Rod (sarcasmo) makes muscle cars do fantastic things.  You'll not find better tunes imo.

Gracias amigo...no one loves a good ol' buttering more than me.