- 11,329
- Marin County
I did some testing with the telemetry on. As stock, as soon as the outside front tire friction value gets close to 100% the same side rear tire does as well, and it's especially pronounced at high speed. I started to guess it might be an aero issue more than anything. I found a post over at the Forza forums that claims to have the stock downforce values of all the cars based on dev information, and the rear downforce of the 996 GT3 is only 105 which is quite a bit less (if the units are the same) than the "race wing" on it's lowest downforce setting (notably, it's also about on par with many cars with no real aero at all...maybe a T10 oversight). So I tried putting the race wing on it's lowest downforce setting and all else being equal, it was a noticeable improvement. Turn the downforce to the middle of the scale and the problem almost goes away. Turn it up to 3/4 or higher and the car handles like I would expect - the front pushes wide unless you really provoke the car's rearward momentum. I verified this by doing high speed lane changes on the highway with the telemetry up. The front tires would always go "red" on the friction indicator and that was it, the rears would stay planted. Moral of the story, if you want to drive the 996 GT3, do so only with the race wing. (I should mention that I also have the widest rear tires and suspension settings copied from the 997 GT3, but that stuff doesn't seem to matter near as much as the downforce). The way those stock downforce tables read makes it look like they are basically arbitrary multipliers used to tweak how much grip the cars have, based on performance data. Why does a normal Huracan have a value of 247? Why does a 1980 Fiat 124 have any downforce?
By a high level observation, the 996 seems to have a higher proportion of front downforce compared to rear downforce than many or most cars in that table, it's about a 2/3 ratio whereas most cars seem to be 1/2 or less. If this is what is causing the problem, I would expect it to be present in other cars with similar ratios. The ones I noticed-TVR Sagaris 62 / 97 [0.639] (I remember this car being almost undriveable in FM4, wonder if the values have been the same since that game...I'll have to give it a try in FH4)
-991 Turbo S 84 /132 [0.636] AWD so maybe less of a problem. I'll try it later
-Peugeot 205 S16 15 / 24 [0.625] With such a short wheelbase, this seems like it could be a total clown car at higher speeds. I'll test it.
-Silvia Ks 1998 51 / 79 [0.646] Very high ratio. I'm guessing this was a design choice by T10 to make it extra drifty
-Lotus Esprit 2002 63 / 99 [0.636] Haven't driven this car much, seems like a contender to have high speed instability like the 996 GT3
I will say that the F50 has the same ratio [0.63x] and that car feels pretty planted, so I don't think it's the only thing causing the instability. Maybe it's just that the Porsche is a somewhat narrow, rear engined car. Whatever the case, there is something contrived-feeling going on. It's like T10/PG started with the characteristics they think the car should have and tweaked various values to achieve it. Mid engine and rear engined cars throughout that list seem to have front to rear downforce ratios of around 0.63, as do the "slidey" FR cars. It's like they wanted the mid engine cars to behave more luridly...which is kind of a shame because my real life experience tells me that an MR car will feel more planted than almost any other setup in almost every situation.
Ok I'll stop dragging everyone through the weeds now.
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