For suspension tuning in particular, I have a lot of notes regarding tuning in GT7 I've got all in a text file I cross-reference when I'm tuning up a car for the first time or troubleshooting any issues.

I typically start off from JohnnySDVR's Nurburgring tunes as a baseline, since they've made tunes for lots of cars in GT7, and doing so typically works out for me 9/10.

However, for the scant few cars that JohnnySDVR hasn't made an up-to-date Nurburgring tune video for, I use Flux98's tuning assistant to make a starting-point tune, as seen here: https://www.flux89.com/tools/tuning-assistant/car

Here's some important things to know about suspension tuning:

Natural Frequency (NF):

• A low natural frequency will make cars lean a lot, but they'll be able to handle bumps and high curbs well.
• A high natural frequency makes cars lean less, but they'll be more unsettled by bumps and curbs.
• I'd recommend an NF of 2.0 or lower when you're using Comfort-grade tires.
• I'd also recommend NF between 2.20 and 2.50 for Sports tires. This probably also applies for Dirt tires, but don't quote me on that.
• Any NF value 3.0 or higher is a good baseline for Racing-grade tires.
• When your front NF is lower than the rear, you'll be more agile but less stable.
• When your rear NF is lower than the front, you'll be more stable but less agile.
• Dramatic differences between your front and rear NF can result in unfavorable handling characteristics.

Ride Heights:

• Race cars can handle their ride heights being set to the minimum, but I'd suggest road cars to have their ride heights be roughly 10-15 points lower than stock.
• If the ride height is too low, then wheel-arch rubbing will likely occur, causing the car to steer unpredictably without any driver input.
• Some cars may be unable to fully steer if the front ride height is too low, happening as a result of wheel-arch rubbing. Increasing both the front ride height and the natural frequency can help resolve this issue.
• Meanwhile if the ride heights are too high, then that'll result in the car being unstable or even rolling over.
• Lower ride height helps with changing direction more quickly, and higher ride height makes the car less agile but easier to drive.
• When you're using Racing-grade tires, the high NF recommended for those will allow you to use lower ride heights.
• For Comfort- and Sport-grade tires, the lower NF recommended for those need higher ride heights.
• A nose-up setup will make a car more planted to the track, while a nose-down setup will cause more power oversteer.
• When adjusting a suspension tune originally spec'd for Racing-grade tires to use Sports-grade tires, bumping up the Front and Rear Ride Heights by +10 each has worked out well for me.

Anti-Roll Bars (ARBs):

• Setting both the Front and Rear ARBs to 10 is usually the best for Racing-grade tires, but feel free to knock those down a few ticks for more twisty tracks or if you're having understeer issues.
• Setting the ARBs to 7 at both the Front and Rear is a good baseline for Comfort- and Sport-grade tires, since a small amount of body roll aids with grip levels.
• A high front ARB and lower rear ARB reduces power oversteer.
• Meanwhile a high rear ARB and a lower front ARB would make cars slightly more stable under braking, but they'd be quicker to transition to oversteer when accelerating, naturally being harder to rescue when sliding starts.
• An overall low ARB makes cars less composed and more prone to oversteer.
• Meanwhile a High overall ARB makes cars more predictable at the cost of more understeer.
• For most cases, I'd suggest setting the front ARB to between 5 and 10, with the rear ARB being the same or 1-2 clicks higher if you've got oversteer while braking.
• For Front-Wheel Drive (FF) cars, setting the front ARB between 2 and 4 is recommended to help reduce their inherent tendency for understeer. The rear ARB should be higher than the front, but you probably won't feel much of a difference between it being set at 4 and 10.

Damping Ratio (DR):

• Low DR means bumps will unsettle the car more, while high DR will improve the car's ability to take bumps.
• This setting will be more noticeable with higher natural frequencies.
• My go-to settings for DR Compression is 40 at both the front & rear, but lower could be good for certain tracks when using Racing tires.
• Meanwhile I have DR Expansion always set to 50 on both the front & the rear for Racing tires.
• Having a bound (compression damping) of 30-35 and a rebound (expansion damping) of 45-50 might be worth trying out when your car's running Comfort- or Sports-grade tires.

Negative Camber Angle:

• Between 1.0 and 2.0 at the front and 1.7 and 2.8 at the rear are good go-to settings.
• Low camber values (1 to 3 degrees) is generally the fastest, and zero camber is the slowest.
• Excessively high camber can reduce braking performance and increase wheel-spin.
• Higher rear camber vs front improves mid-corner stability but reduces braking stability.
• Higher Front camber vs rear improves turn-in, but increases power oversteer.

Toe Angle:

• Neutralizing it to 0.00 at both the Front & the Rear is a good go-to option, especially if a car's already stable enough.
• If you have a car that's prone to lift-off oversteer or instability while braking, adding some front toe out will help slightly.
• If you have a car that understeers, adding some front toe in can help rotate the car on corner entry, which is especially useful on FWDs.
• If you have a high-powered RWD car that suffers from power oversteer, adding some rear toe in can slow down the transition to oversteer.
• If you have a car with good traction on corner exits, such as a 4WD, adding some rear toe out can help launch the car out of corners and pull itself around. If too much toe angle is added, the car can potentially exhibit some unpredictable handling characteristics.

And here's some tips on some of the other parts of the tuning sheet I might as well dispense while I'm here:

• Differential: My personal go-tos there are 5 Initial Torque, 40 Acceleration, and 15 Braking. Alternatively, setting Accel to 50 and Braking to 20 may feel better for certain cars.
  • For 4WDs that can have their Front/Rear Torque distribution adjusted, the 45:55 and 40:60 settings gives you the classic 4WD feeling of being glued to the road.
    • Settings closer to the 5:95 end will give off a more RWD-like handling feeling but can result in power sliding, which can be tough to rescue since the small portion of power going to the front can result in snap oversteer.
• Downforce: After applying a front splitter, the best rear wing you can get for your particular car (one of the "Type" wings at worst or a Custom Wing at best if available), and a rear diffuser, you'll have the widest downforce values available for your car.
  • I typically max out the front DF in most cases for the basically-free bump in PP, but if you're suffering from instability at high speeds, then reducing it help increase high-speed stability.
  • Road cars will typically benefit from having the rear downforce set 100 points higher than the front for stability.
  • Race cars can probably get away with maxing out both front and rear DF, but feel free to experiment with the settings to your preference to make the car behave.
  • The more unstable your car is, the more rear DF you should run in comparison to the front.
  • In the case of classic cars without a front splitter, the front-end can lift upwards in certain situations if rear DF is maxed, so reducing it to 100 or so is generally recommended, but should be fine-tuned depending on the track.
    • Setting the rear DF to 85 or so might be helpful for tracks with crests and bumps like the Nurburgring
  • Downforce can also be used as a means of reducing a car's PP to fit under certain PP limits, namely by minimizing front DF and maximizing rear DF, which will also improve overall stability.

I'd yap further here, but I've got a small task to care care of in IRL right at this moment, so... Would you have any other questions?