Help tuning suspention, McLaren P1/other vehicles with race suspention stock

So I have played every Forza game extensively, I race with only the braking line and no clutch but otherwise everything off, I upgrade and “tune” all my own cars but only ever mess with gearing, aero, differentials and sway bars.

I don’t really understand alignment and springs/dampening
Now to clarify, I totally understand vehicle alignment but I don’t understand where the best settings are for Forza, sometimes I will look at telemetry and see a wheel going into positive camber so I will add some negative but sometime it makes the car weird and I just leave it…Forza doesn’t really seem to translate into real life tho as racecars IRL run 5+ degrees of -camber all the time and Forza doesn’t go that high.

Springs and dampening however I can’t wrap my head around, I get how everything works (tuned my mountain bike fork, air-spring plus highspeed/lowspeed compression and rebound, pretty easy, also bought a car on coil-overs with the dampening maxed on 32/32, turned it down to 16 and the car was bouncy and floaty so I clicked it up till I got to about 24 and it was good, 24-26 so I understand the concept) but I always mess up the front to rear ratio or the spring rate to dampening ratio and it gets all goofy and I don’t know what to do, in most situations the race suspension upgrade is fine but on older race cars that have the adjustable suspension stock or something like the McLaren P1 I have issues.

I wish there was an easy “stiffen it up” setting

Trying to tune the P1 right now (In Motorsport 5) and stock it is way to soft but if I stiffen the springs 200ft-lbs each it goes all weird and if I raise all the dampening like 5 notches it feels better but still not right, after playing around with everything, upping the anti roll bars, reducing the rear spring rate some it still isn’t right so I thought heck and I used the calculator featured here now this seems balanced but to stiff, it doesn’t need to be this stiff, how do I reduce it evenly? Also seems a bit tail happy but maybe just because it’s to stiff overall.

I basically just have trouble with the spring to dampening ratios and rebound to compression ratios and if it’s off it handles all goofy.

I should add, I KNOW when/how to make a small anti-roll bar adjustment by how the car acts in steady state cornering, I KNOW how to tune Aero by how the car handles in fast turns vs slow, differential lock up is a little harder as issues only seem apparent at the extremes, but dampening I don’t really know how to tell what needs changing in isolation, I can’t tell what adjustment is off so I’m just shooting blind.

Also this calculator said to set 61% brake bias, that seems extreme to me? I never have an issue with the rear locking first

Also some times drastic changes are made to 1 anti-roll bar and not the other or to alignment settings and I don’t really understand why, some times the front and rear rebound stiffness are upped and the front bump but the rear bump is left stock, again I don’t understand why.

I haven’t found a good, empirical way to set dampers. Best method I’ve developed is test the car on a bumpy track (ex: Rio National) and on one with a rough surface (ex: Sebring) and try to find settings that work well in both scenarios. Not remotely scientific, and leaves a lot of room for confirmation bias to color your results. Lately I’ve just been setting them at Bound: 4.0 and Rebound: 7.0 and having done with it.

Springs are (usually) a lot easier to set. I have my own formula worked out, but setting the front springs to ((car weight / 2) * weight distribution) and the rear springs to ((car weight / 2) * (1 - weight distribution)) will get you a solid starting point without a whole lot of fuss.

Lastly, I distrust all the calculators I’ve messed with. There’s a ton of misinformation about how things work (reference: in-game description of toe settings), a ton of “gamer voodoo” influencing methodology, and nobody (that I’m aware of, at least) has published any test data to back any of it up.

Really-lastly: 61% brake bias is absolutely asinine in FM. Most cars end up somewhere in the 44-48% range. I suspect (and have not tested, so don’t ask for my test data) that “50% brake bias” in FM really means “factory brake bias”, and we’re adjusting from there. Since most cars have a slight front bias, moving it rearward from “50%” would make sense.