Physics discussion thread

I find the FFB in AMS2 has a very strong self correction and that conveys oversteer even when there's just a little slip. Custom FFB files fix this to a large extent for me.

 

Over time the physics and tires in AMS2 have gotten much more believeable. I feel, there are still 2 things that could use a bit of improvement.
1. The sudden snap of extreme oversteer that happens during aggressive corner entry. If that could be toned down a bit it would be appreciated. Any yes, this is after a lot of time has been spent tuning rear diff, shocks and brake bias.
2. Increasing the rear tire spin during launch from a standing start. Anyone that has done motorsports IRL, knows how easy it is to spin the tires at a standing start even with cars that have low whp/wtq. Heck you can spin grippy tires even with a 150whp MX5 pretty easily.

I love how the game has continued to evolve over the years. Keep up the good work Team Reiza!

 

I hadn’t thought about spinning tires from the start but it’s very true. Most sims are way too easy to start. In my IRL car with 400hp the tires will spin like mad if I just mashed the gas pedal. I know they’re not racing slicks but I still wouldn’t be able to just mash the gas.

 

Speaking from experience, it happens on slicks too.

 

One of the most exciting things I remember from the old sim racing days is driving on two wheels.

When you take a corner or hit a curb so hard with certain cars that you almost tip over. (Or actually do tip over.)

In almost all modern simulations, the cars are practically glued to the track. Yes, they rock back and forth, but you can be sure nothing will happen.

I think this physics significantly increases the range of possibilities for how hard you're willing to drive. The risk leads to a rush of speed.

 

You clearly never drove the Porsche Cayman in ACC. That thing lands on its roof if you look at a curb wrong.
Here is a clip of me flipping the car over at Copse:

Happens all the time

 

You're right, I really didn't get to play ACC properly. The counter says 50 hours, but I probably spent 45 hours just tweaking the options.

VR and ACC are like Tom & Jerry.

But flipping a Cayman? That shouldn't happen, right? AMS2 has a lot of classes, there are definitely better examples.
It worked best with LFS, RBR, RF1 & 2...etc...

 

Just tried V1.6.9, the tires on the few cars I tried (GT4 and GT3) are much more relatable and the sudden unpredictable snap during corner entry is gone once the tires are in their operating window. They now behave like in real life, where if you overload the fronts during corner entry you get understeer like you're supposed to, and if you modulate the brake you can induce oversteer depending on how much or little brake pressure you apply.

You can now lean on the tires during cornering and get the car to dance at the limits with some slip angle using the throttle and the brake before going overboard. Tire break away is a bit more progressive and managable. I love it.
Well done! Team Reiza you've worked you magic and done it!

 

Also just got a chance to try out the Nascar stock cars Gen 1, 2 and 3.
They are a pleasure to drive, so much fun. However I did notice the Gen 1s tended to overheat the rear outer tire if driven aggressively with a bit of slip angle.

Finally we have wheelspin from a standing start!!! And you can modulate the throttle to control the level of wheelspin and use it to control your acceleration when launching a car, just like real life.
YES!!!
Between V1.6.9 tire model updates and the update brought us multiplayer enhancements, we're getting an amazing sim that's creeping closer and closer to real life. Personally, this is the best AMS2 has ever felt.

I think the next thing I would like to suggest that could use a bit improvement would be:
1. Shock adjustments. On a lot of cars, it feels like, you have to make wide sweeping changes to the values to get a small change in vehicle dynamics. IRL, with good quality shocks (Ohlins, MCS, KW, Koni) a few clicks of compression or rebound can completely change the attitude of a car going in or coming out of a corner. 2 clicks of rebound can change a car from too much lift throttle oversteer to just the right amount. Adjusting the shocks in AMS2 currently feels like you're adjusting low quality shocks IRL (BC Racing, lower end Tien), meaning their range is so low you have to make massive changes in adjustment to feel a change while driving.

 

I loved the new update and last time i said it's 90 there - now i claim it's 95 %.

I was very impressed with the Audi R8 road car in Nords tourist layout.

The GT3's have improved as well and they require a tad more skill and fitnesse now.

There's still an issue in slow corners - it's super easy to shift the car weight on front and drift controllably thru.
The rear doesn't stay planted even without any pedal input. Feels like four wheel steering / sliding.

 

To me if feels like the tyres have tremendous amounts of flex in the carcass. Visually this is backed up, where on a lot of cars the tyre almost seems Flat when cornering. I am aware that there should be flex, but on a formula 1 car for instance to have the rim almost flex through the floor, it is not accurate. And if that sidewall visual is being represented on the physics side of things as well... It explains a lot of bouncing and stuff.

Incidentally this might also be why the classic stuff handles so great in AMS2, as the tyres are soft, almost cross ply...

I have done the same R8 and Nords combo you have and I actually DID have the rim through the floor on replay. Again IDK if the visuals match the physics, but if they do it certainly explains the behaviour (and also validates several proffessional drivers opinions as well on some aspects of AMS2 handling - tyre wise).

 

I did notice GT4s and GT3s were able to better adsorb bumps using the same pre-V1.6.9 setup. I suspect this might because tire sidewalls might slightly be softer after this update? Usually the side walls being slightly softer (at least in real life) makes the break away at the limit of traction more progressive and less snappy. So I wonder if that is what Reiza has done with the new model.

Honestly for production chassis based cars, I think this balance they have struck is almost perfect. The few cars that I have tested, drive so naturally compared to my amatuer experience in real life. Personally I could careless how much they flex visually from outside as long as the driving feels natural from the driver's seat.

 

What’s this rubbish about tyres flexing… every armchair sim physics expert knows they are solid, stable, and you only need 3 points of reference to be realistic.

 

Hello community! I finally registered so I can chat =)

Thanks to the developers for the free camera, I hope they improve it =)
In the meantime, I have some questions about tires...

Is that how they work??

In the video the tire pressure is 1.50.
I checked the tires with 1.8, but the situation is typical.
This is some kind of exaggerated realism... A tire with such inertia of movement will not spring as much, in addition, the jumps are very sharp, the reaction range is very low, which is why the reaction to compression is huge.

It's the same on other cars, for example on Kart X.

 

Couldn't tell exactly if its softer or stiffer based off this update, but it is definetly different. Softer sidewalls do usually give more feedback and a more progressive breakaway, until a point when they hit their "maximum" then it goes. I suspect in a simplified way, this "point" is whats been tweaked in the new update?

Visually I could care less either honestly, its just the only definitive way of knowing whats happening, so if it matches the physics great. But on the formula cars and prototypes it really does seem to flex too much, at least on the vertical axis. Oddly the horizontal seems fine, which does seem to fit in with some of the racier cars being "bouncy" in some areas, to me at least.

It seems very springy IDK if thats accurate for the tyre or not, but looks to match some feelings?

 

It's impossible to say outside knowing the code on how well the replay / visual representation matches the driving physics. I have seen cars going backwards from standstill on flat surface without tires moving... so I personally don't trust it that much.

 

You can get objective data about carcass flex by analyzing the “Tyre Height Above Ground” channel in telemetry, running SimHub or Motec (don't know about other apps)

PS: Data default is in meters

 

I don't feel it. It doesn't affect the FFB. Today I'm riding the Valkyrie, and I can feel the tire deforming horizontally; I never felt that before. But there's a vertical effect here.

While messing around with the camera, I noticed the car squatting oddly and then lifting on two axes when freewheeling. I could have dismissed this as body roll and weight balance, but this squatting and lifting effect occurs even at low pressure, where these effects are minimal. The tires shouldn't deform like that, and this odd squatting is also a factor. Out of curiosity, I looked at Project Cars 2; it has the same effect, only it affects the body and suspension more. Visually, the tires in PC2 seem to be working correctly.

Am I correct in assuming that with such a light load, the tire should simply ride in the same compressed position as it would at rest? This could be a bug in the update, as a lot of work is being done to improve traction.

This is weird!

I also noticed an interesting solution for optimizing the game!
The low-poly tire model doesn't rotate, but its texture, brake disc, and wheel rim do. For example, in BeamNg, the low-poly model rotates, and every vertex of the model affects the suspension in the XD car. That's great for AMS2!

Do the developers read the forum?

 

I wouldn’t get too hung up on the visuals.
While attempting to give an immersive experience in replays to closely match what the core behaviours of the car in motion represent. They are not going to be 1 to 1 with the physics of the tyre and suspension.

A example of that is the occasional build of a car model that has its tyre clip through the body work ( something you probably haven’t experienced yet being newer) , this is obviously not physically happening as if it was, the guards would be ripped apart and the tyre shredded.
It’s just a visual misalignment or too pronounced movement that usually gets tidied up eventually.

 

One thing I noticed in last update is that the revisions made make car contacts in wheel to wheel battles now are much more - but really much more - realistic. And spins too.