As I said yesterday let's talk about tire compound.
Tires are one of the most important parts of a car, and the biggest expense in racing I think because of a flawed performance-durability ratio.
Tires produce grip by:
-coefficient of friction between tire and racing surface;
-suspension design;
-tire construction.

I've been using medium hardness compounds in 1/8th since I started racing 10+ years ago, first because the medium compound was good(Medial Pro tires) and because you couldn't find soft compounds sold here. So I adapted my way of tuning around that medium compound, kind of like you saw in F1 with different tire brands catered to different car/suspension designs.

As suspension design is set by the designer, it can't be easily reverse engineered to understand what level of friction it works the best, but as you may guess is set to a broad spectrum/aimed to what rules state about tire construction. Tire construction is somewhat limited, we have different compounds and tread patterns and that's it. Tire dimensions are pretty much locked and usually there's a insert that works and no one deviates from it. Friction can be changed by chemical additives but I am against them and they are illegal, except in 1/10th scale. That leaves another option to have more friction, increase tire load.
Coefficient of friction is f=F/W, where F is the force needed to make the tire slip and W is the weight exerted by the tire to the racing surface. In simple terms, chemical alterations to tire construction change F and mechanical alterations change W. So if one can't change the compound(chemical) that leaves the mechanical part, most add weight(XB8, MBX7), others add roll(more weight transfer by roll centers/stiffer suspension). As you can guess, adding weight is good to grip but bad to everything else performance wise(if the driver is OK with the loss in engine performance I see no issue). On the other hand, roll centers and suspension tuning have no negative impact in overall performance if tuned to tire construction and grip because if the car grips the same as it would with softer tires it would just roll more and as you can control how quickly and how much weight it transfers performance is the same albeit more difficult to reach.

On the spreadsheet, the harder the tire compound the lower the Suspension Frequency and vice versa. Hope that with more knowledge one can suit tires and setup to available grip and get more life out of tires.

More damper information.
Focused on damping ratio lately, cool stuff but complicated to do. First, the equation is quite advanced and second it requires a shock dyno(unless someone knows the damping coefficient for our shocks with different shock oils and pistons).
The dampers we use on our little cars are linear, there's zero information that supports tapered pistons work and little more can be done than tuning low or high speed damping and the point where the damper "packs". You can tune to most of the track layout and that's what you should do after you filled the spreadsheet and copied the setup to your car, the spreadsheet is just a starting setup(in the right way I hope).
A new version is uploaded, just changed a discrepancy.

Wish everyone a happy new year!

Tip to those buggies that have both short and long arm setup possibilities like the MP9 and THE Car White Edition. When you go to short or long arm change the upper link length to maintain proper camber gain. With the shorter rear arms on the MBX7, the rear upper links were very long(the point were the link attaches on the rear shock tower is inwards than the lower inner hinge pin) causing a very aggressive rear end with low traction. Drivers didn't adjusted the upper link length because they have hardwired that a long upper link always equals more traction. Something like this happens with the MP9, drivers complaining of not enough steering. Move the rear upper link one hole up on the shock tower and see if you now have more steering.
The rear upper link angle is a powerful adjustment, use it and learn what it does to you and your buggy.

Wide chassis vs. Slim chassis.
Manufacturers are pushing one or the other, I believe they can work the same in different conditions.
Wide chassis have more flex, anything that unsettles the car is filtered through both suspension and chassis flex. They also have the components spread a little more than a slim chassis which means when a wheel goes through a bump the suspension has more "inertia" and the bump is absorbed better than similar shock package on a slim chassis.

The slim chassis has less flex inherently and requires a better shock package setup to absorb the bumps as good as a wide chassis. Performance differences between the two types is not night and day, I see the wide chassis as a tuning option because tracks around me aren't that bumpy and jumps are "small".

Tire wear pattern.
Where your car tires wear the most? Inside(towards the center of the car), center or outside(towards the outside of the car)? Do you have to run more camber to balance wear?
Tire wear pattern changes with tire load as you know so when you have a very spread wear pattern starting from the center of the tire you know the suspension is using all the grip the tire has to offer. Again, if you have to run more camber to balance the wear something isn't right, let it roll more.

Very interesting! Thanks for posting!
Keep up the great work!

Thanks for your kind words and glad you liked it.

If all goes well, tomorrow or next Monday will arrive the guide that taught me most of what I know. As soon as it arrives I'll share with you.

*edit* Arrived, and there's nothing more than I already wrote here, I'll check my other literature because there was a topic I wanted to share. *edit*

Camber gain.
One of the most powerful adjustments in a car, it really makes or breaks a car's handling.

The common misconception of longer upper link=more grip is somewhat true, depending of what the driver is trying to achieve the car has more "traction". Let me explain, camber gain affect mainly overall response. If a car has long upper links the car is lazier and is very controllable, also my experience shows that it can be aggressive because the rear doesn't bite well. On the other hand a car with short upper links is more nimble and bites the track harder.
I also tune the length relative to amount of grip available, the more grip the track offers the longer the upper link because there's a point where short links become too twitchy to drive and I go for a step longer.
Like racing on astro, if you use short links the car would traction roll every time you sneezed on the steering wheel or long links on a low traction dirt track, the car would feel like it's dragging a boat anchor.
Now I can't find where I saw a how-to draw camber gain throughout suspension travel but the rule of thumb is to have camber gain on compression and camber loss on extension, achieved with lower inner link position or higher outer position. Also since I had the rear shock piston breakthrough I tend to gravitate towards the outer hole in the inner upper link position(works really well in the TLR22).

Sway bars or Anti Roll bars.
As the name implies they hamper roll, equalizing both sides. We use them mainly to keep roll centers from migrating too much outside of the best working positions(they move when the car rolls). Now the thing that I found today looking at the cars I have with sway bars is that only two(Kyosho ZX5 and Mugen MBX5R) keep the rear bar mounting balls perpendicular to rear arms when the suspension works, all of them keep the front bar mounting balls almost perpendicular throughout suspension travel.
I'm going to think more about this, just found it a couple hours ago and want to know if this is supposed to happen, maybe not because the bar works by forces twisting itself, if the ball end is pushed back then the force the bar exerts towards the arm is somewhat lost, causing inconsistency in handling.

Later this evening, radio adjustments.

Part 2, radio adjustments.
Personally have 2 profiles, Mellow(or Main) and Aggressive(or Qualifying) to use in different situations in a race. They are a bit different to each other, I know most just change steering D/R or ATL but mine also have different expo values. So, during practice I test the fastest profile and make changes to both the car and radio until I'm satisfied with the speed and feel, that will be my Aggressive setup. Then I back out throttle EPA or add throttle exponential, use less D/R or steering exponential until I'm satisfied with consistency and pace and save that profile as Mellow.
That way my nerves don't get in the way the first laps and if I need more aggressiveness once I pit for fuel I change the profile. This is easy to do on the hacked GT3B, the M8 and CRX are not so easy, I use mainly ATL and D/R on those radios because those buttons are easy to reach.

P.S.:BTW I've driven lots of 1/8th buggies with Futaba S3003 and 4.8v Rx packs, for roughly half an hour they do OK on the track then the battery packs drops bellow usable voltage. It helps that my local track is wide(13ft lanes) and not tight at all, but at least newbies aren't in a rush to upgrade servos. The S3003 work not so bad with voltages upwards of 6v
Also my servo recommendation is:
for 1/8th buggy- ST/TB at least 8kg and .15s, personally anything above 12kg and below .1s is too expensive for the performance provided. If you feel otherwise maybe your car understeers

Okay back to my main PC! Old spreadsheets are back for those that like certain layouts(v2.2, v2.7).
Working on some small additions.

Version 2.9 is up. Expanded the load transfer equations and shuffled things a bit.

And now v3.0 is up.
See how the front tires have less load transfer than the rear tires? Crucial to make a good setup and not gain steering by running a loose rear end or gain traction by removing grip from the front. You can tune that with roll centers and roll bars, being these the most effective setup options for 4WD cars.

I've been busy testing my cars at the track, I've made changes on the JQ that I didn't like (and I have a better understanding of the spreadsheet results) and the TLR 22 Mid motor is very loose on the dirt track (shorter rear camber links are in order).
The changes I've made on the JQ was using the mid hole in the rear arm to attack the shock. Lost a great deal of on power traction but gained nimbleness, steering response and turn in speed compared to using the outer hole to attach the shock. While the turn in is a result of increased rear droop the change in Motion Ratio was counter intuitive right? That's what I'm trying to know today at the track.
Luckily that messes with the roll stiffness and that equation is not right. Got to check that later tonight.

V3.2 uploaded, improved the roll stiffness equation and shock piston starting setup equation. See how my setup is balanced front to back Still haven't got to the track but hope to be there in one hour.
Found others explaining that softening one end of the car lessens weight transfer, so when I went for the mid hole in the rear arm for the shock my JQ transferred less weight side to side and that's why I gained steering, as I said before tire load is very important and it should be what we should be after and not straight to softening front or rear springs.

Fresh from the track, it was back to how it was I can't believe how much difference that change did to on power traction, now it almost pushes on power and has actual good traction, using the outer hole in the rear arm -a higher suspension frequency- a complete opposite of what you read around here.
That's why most setups and complaints are easy to debunk. Racers complaint that X car has no traction on/off power/doesn't steer, that the front/rear suspension was softened and it doesn't work so the car is a POS. Well, there it is, make the car press the tire down, increase tire load not decrease it.
Another thing I want to address:
-Springs and pistons control chassis up and down movements, roll centers and ARBs control roll and kick-up and anti-squat control front to back and vice-versa weight transfer. If you do suspension tuning by tuning roll with springs/shock oil like 95% of racers out there then your car will always look "bad" on track. For example, ever see a MP9 with the stock setup going around a track? Looks like a pillow and has a reputation for being the King of rutted tracks. It has the total package, years of R&D, comprehension and understanding of what's going on the track and almost every buggy out there "can" be tuned to perform as good as it is but racers are lost in the shock and roll centers voodoo and mumbo jumbo. My Programming teacher told me to break a big problem into smaller ones. The car doesn't soak the bumps? Thinner shock oil, still too much then softer springs front and back to maintain balance. Doesn't grip? Induce more weight transfer by ARB or roll centers. Roll too much? Less weight transfer... Don't change shock package to control roll.

Motion Ratio(MR) again:
They don't have to be equal front to back, if the shock package is balanced front to back its all it matters. With that said, a good approach would be to run a setup that doesn't require an out of this world shock oil/piston combo, see the spreadsheet for a recommendation, and desired droop.

I'm happy when I see more and more setups with different front and rear shock pistons and racers trying to think outside the box. That's why I do this, to make everyone go fast and have fun.

New version is up, mind you the roll angle calculation doesn't account for roll bars. But with that data you can guess what combination is suitable, as you can see the front needs less than half the weight transfer to roll as much as the rear and I'm running a 2.5mm bar at the front and a 2.8mm at the rear and the front still rolls visibly more than the rear, it's ok because I'm happy with track manners.

Thank you all, combining both thread's views are a little more than 3000 and it means a lot to me. Any question or difficulty while filling the spreadsheet let me know, also any setup question or if you want to question my method is OK.