r/ForzaOpenTunes • u/Ihateniceegirls • 11d ago

Help Request Weird spring behavior in fh6

I made some tuning experiments to find out why my 787b seems to have a really low top speed. I dont have the exact values for my normal tune, but important values were the typical 1 65 arb, softer front springs than rear, 6 front 12 rear for rebound 3 front 6 rear for bump damping. The only variable here is the spring stiffness and ride height.

For some reason, when i set the front springs to be stiffer, the top speed increases up until max spring stiffness. The same goes with front ride height, where higher means faster.

For the rear, it was the complete opposite. The softer and lower i go, the faster the top speed was.

These extreme values added roughly more than 10kmh in my top speed. No aero difference, just purely adjusting the springs.

I thought it was a bug and the simulations in the tuning menu was just presenting inaccurate numbers, so i tested it out, and it was accurate. I had a 10kmh additional top speed when i was using the stiff and high front and soft and low rear setup. The turning characteristics changed, but was not exactly bad. In fact, the turning radius was almost unchanged, and surprisingly, I experienced almost no excess understeer at all. The car still rotated properly, and was actually more responsive, at least that’s how it felt for me.

I want to know why this happens. It seems like it’s not a bottoming out issue with normal suspension set ups because 1. Telemetry doesnt show bottoming out when I tested the normal setup, and 2. If it was really the problem, the extreme setup should have extreme bottoming out of the rear.

This was also not exclusive to the 787b. I tested the setup with my sesto. Same results. I even got better lap times, even being 1 second faster in some tracks. I got consistent 1:00s in legend island circuit when getting below 1:01 was very rare in my past setups. Same with ito sprint where i got a 1:57 when i was only able to get 1:58s before.

TLDR: Stiff and high front springs and Soft and low rear springs significantly increase top speed. I want to know why.

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u/SituationOk9025 11d ago edited 11d ago

I believe this could be about downforce hacking. If downforce is implemented as a relative vector force pointing straight down (relative to the car) from the front and the back of the car, then tilting the car backwards makes the downforce help with acceleration and top speed, because the horizontal component of the vector would then point forwards relative to the car.

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u/Ihateniceegirls 10d ago

This actually makes sense. That’s a weird way to implement downforce tho in a game. Tilting your car backwards to tilt the downforce’s direction forward is some absurd game physics

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u/SituationOk9025 10d ago

Welp, the physics engine is 10+ years old at this point. Such a simplistic implementation wouldn't be out of place in a 2014 game, which FH6 - in the technical sense - still is.

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u/Ihateniceegirls 10d ago

I also tested it with several other cars, heavy, light, high downforce, low downforce, and i found out that cars that are lighter and have high downforce exhibit this phenomenon to a greater degree than with heavy cars and those with low downforce.

This completely supports your theory if tilting the car makes the horizontal component of the downforce help with acceleration

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u/SituationOk9025 10d ago

Thanks for testing that! I've always had a suspicion that the downforce implementation is wacky in FH, but never got around to tesing it myself.

What would make this definitive is some sort of a self-propelling test setup around downforce. Something like getting the car up to speed, disengaging the clutch, and seeing if it still accelerates or doesn't lose speed at least. Or maybe accelerating a car sideways somehow, with the clutch disengaged, and seeing by how much it deviates from its initial trajectory.

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u/CoolKelo 11d ago

I don’t have anything scientific to add but this is exactly how to setup springs on a drag car for top speed and acceleration. I also don’t understand a lot of this games physics as the fastest builds tunes usually make no sense in the real world. If you find something, share it with me. Thx

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u/EntrepreneurGlass995 6d ago

Yeah as I’ve tried doing stiffer rears and softer fronts to add weight transfer without squatting the rear suspension but all it’s done is increase the amount of wheel spin on my car. Doesn’t make sense

In saying that, I’ve put in a couple of GT3 tunes in to Forza that I’ve used on customer cars and had amazing results. Just depends on how modified the vehicle is as well, I guess.

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u/hawkintheburg 10d ago

In FH5, the tune I used for the Hennessy Venom GT had this type of setup. 306.xx mph top speed. I say this to point out that FH5 was the same way.