How I've tuned the Lamborghini Aventador is a good example of how I think about tuning a car where the majority of the weight is over the rear axle. My first experience with this was when I raced the Modern GT league with the Dodge Viper, where I had a tune that was prone to snap oversteer. If you watch this race replay from that league you can notice that I struggle with it in the last turn (e.g. on lap 1, 1m 36s into the video), as well as on the last lap I lose 3rd place after the sweeping left hander around the lake (6m 13s) because the car oversteers coming into that turn and I have to slow down to keep control.

When I first tuned that car, I used the approach learned from ForzaTune. If you punch in the numbers for a fully upgraded Viper GTS-R with default downforce, the only suspension setting that is higher for the rear end is the damper rebound. The springs, ARBs, and bump stiffness are all softer. In my experience this tends to create a tune where the car “sits down” on acceleration, giving you lots of grip in that situation. It’s also stable and easy to drive, but with a tail end that’ll snap if it loses grip.

I struggled in the Modern GT league with that Viper for the first few days, then decided to go back to the drawing board. Instead of going with the FT approach, I tuned it based on the weight distribution, inspired by some of Stella Stig’s tuning videos. This means that springs, ARBs, rebound damping, and bump stiffness are all lower in the front and higher in the rear. How much higher/lower depends on the weight distribution, in the Viper it’s fairly even, whereas the Aventador has more of a gap since the weight distribution is 45/65 percent front/rear. With this approach the car doesn’t grip the same way during acceleration and it is perhaps less forgiving, but my experience is that it often results in a tune where throttle and braking inputs allow for subtle changes in control of the car, and that oversteer is much more predictable and controllable.

A couple of more things to note about the Aventador’s tune is the brake balance and center diff balance settings. I’ve moved the brake balance slightly towards the rear. This will often result in some turn-in oversteer if you trail brake, but it also allows you to trail brake quite heavily. For instance coming into the first turn at Lime Rock Park, I can start braking about where the marker cone is on the left side, which seems to be a lot later than many other drivers. However, I’ll then be on the brakes something like halfway through the turn, using that slight oversteer to help the car around the bend.

When it comes to the center diff in the Aventador’s tune, I experimented with decreasing it to 55% towards the rear, and also increasing it to 65%. In both cases I found it to introduce slightly more understeer than where it’s at (60%). Moving more power to the front wheels seemed to make it understeer like a FWD car, whereas going in the opposite direction it appeared to understeer because the rear wheels have a lot of grip and therefore “push” the front wheels to lose grip. I decided to keep it at 60% and have not dialed out all the understeer during acceleration, partly because the way I drive this car is to use the turn-in oversteer to point the car in the right direction and then just hit the “Go” button. It makes for a lot of fun driving, but will fail massively if you go on the throttle too early, unfortunately.

From the tune settings it is also clear that this car is not great for tracks with long straights. The plan was always to have max downforce, but I also found that I could install the sport transmission while staying within the 800 PI limit of the Ultimate GT League. I then altered the final drive ratio to improve the car’s acceleration. For power tracks, I have a Merc SLR that’s similarly tuned but with all engine upgrades and no wings (that tune is shared, as are all the other tunes mentioned in this post).

Should you want a car that’s more well-behaved, experiment with moving the brake balance back towards the front. You might then need to trail brake less, and also try to dial out some more understeer. The car can perhaps also be adapted for other tracks by reducing the downforce and changing the final gear ratio.

Upgrades:
The tune has no drivetrain nor aspiration conversions. Engine has no upgrades. Front & rear tire widths are stock, front & rear rim size is stock. The following upgrades are installed:

• Race front bumper
• Race rear wing
• Race tire compound
• Rims: XD9 or equivalent
• Sport transmission
• Race diff
• Race spring and Dampers
• Race front & rear ARBs
• Sport weight reduction

(edit: changed the topic to reflect that it's a grip tune)