Physics thread

[mister dog]

I am not complaing about you but there were a lot of people on the last pages talking about speed and consistency problems and i also just giving you my opinion everyone should make their FFB as they want to. But what i want to say is dont talk bad about the FFB if you dont understand they way it works and why it is soo light etc. I dont want to offend you just the guys talking about unrealistic FFB and FFB which makes them slower it is just fine as it is. If it doenst fit you you have millions of options which is great

Cheers and sorry for coming off a bit harsh; morning temper

 

[panjandrum]

...power on oversteer yes. Lift off oversteer, no, it should trim the front not get the back stepping out even with quite sudden lifts.

We may be talking somewhat across purposes here. If you look at that video at the turn at 5:30ish, you'll see the car behaving very much as it does in AC actually, a really nice wonderfully controllable lift-off-oversteer that does not require braking or flicking to get it to happen - and that's the key thing that seem to be missing in pcars, where for some reason a brake or a flick is necessary to initiate. As soon as you do that, the wheel grabs, pulls, the car comes around pretty much as it should. It's just that it won't initiate without those! Pretty much anything I drive in that game that is either MR or RR simply plows straight ahead upon throttle-lift. It's just unconvincing and feels terribly wrong to me at this point. We don't have the C4 in pcars unfortunately to try them side-by-side, and I think we both agree that would be a bit useless anyway. You can see by the attitude of the car and the way it moves around the corner that he's simply lifted a bit to let the nose tuck. Anytime you do this it is lift-off-oversteer; not (hopefully not!) snap-oversteer, which you don't ever want to happen accidentally even at lower speeds because once it truly snaps, it's darn near impossible to catch. Mild lift-off? Easy. Aggressive lift-off, harder but very useful if you can do it. Snap? Unless you've used that to purposefully execute a low-speed tight turn you're probably in trouble. So when I say that lift-off-oversteer doesn't seem to be modeled in MR or RR cars properly, I'm not just talking about snap oversteer. (Although that's a very handy way to tell if a sim models lift-off-oversteer well.) Any car with a good chassis and balance will lift-off-oversteer a bit, and this is not a bad thing. If the C4 didn't have any lift-off-oversteer at all it would be an unbalanced and ungainly car to drive, and I doubt that's the case. Driving that car in AC and it feels like the wonderfully balanced machine we keep reading about. I'm drooling over those things for sure! If you are a fan of that car then definitely grab AC and give it a go. It's very rewarding.

I really can't wait for the YB to come out. I can lift-off-oversteer that chassis in my sleep. I'm hoping to be proven wrong here, because I really want to like pcars, but I'm picky-as-heck about a sim modeling this correctly!

 

[mister dog]

So Panjandrum... Have you played around with the diff settings already?

 

[Scaff]

We may be talking somewhat across purposes here. If you look at that video at the turn at 5:30ish, you'll see the car behaving very much as it does in AC actually, a really nice wonderfully controllable lift-off-oversteer that does not require braking or flicking to get it to happen - and that's the key thing that seem to be missing in pcars, where for some reason a brake or a flick is necessary to initiate. As soon as you do that, the wheel grabs, pulls, the car comes around pretty much as it should. It's just that it won't initiate without those! Pretty much anything I drive in that game that is either MR or RR simply plows straight ahead upon throttle-lift. It's just unconvincing and feels terribly wrong to me at this point. We don't have the C4 in pcars unfortunately to try them side-by-side, and I think we both agree that would be a bit useless anyway. You can see by the attitude of the car and the way it moves around the corner that he's simply lifted a bit to let the nose tuck. Anytime you do this it is lift-off-oversteer; not (hopefully not!) snap-oversteer, which you don't every want to happen accidentally even at lower speeds because once it truly snaps, it's darn near impossible to catch. Mild lift-off? Easy. Aggressive lift-off, harder but very useful if you can do it. Snap? Unless you've used that to purposefully execute a low-speed tight turn you're probably in trouble. So when I say that lift-off-oversteer doesn't seem to be modeled in MR or RR cars properly, I'm not just talking about snap oversteer. (Although that's a very handy way to tell if a sim models lift-off-oversteer well.) Any car with a good chassis and balance will lift-off-oversteer a bit, and this is not a bad thing. If the C4 didn't have any lift-off-oversteer at all it would be an unbalanced and ungainly car to drive, and I doubt that's the case. Driving that car in AC and it feels like the wonderfully balanced machine we keep reading about. I'm drooling over those things for sure! If you are a fan of that car then definitely grab AC and give it a go. It's very rewarding.

I really can't wait for the YB to come out. I can lift-off-oversteer that chassis in my sleep. I'm hoping to be proven wrong here, because I really want to like pcars, but I'm picky-as-heck about a sim modeling this correctly!

Then I'm not sure what is going on in pCars for you, because in terms of using a lift to get the nose tucked in to then allow you to get back on the power and should you wish initiate oversteer then yes the cars do that.

Now as far as the 4C goes I can assure you it doesn't do snapy list off oversteer at all (as is also described in the Evo piece), hell you can use even sudden lifts in one to get the nose in, but it never gets more unbalanced that than.

As far as "Pretty much anything I drive in that game that is either MR or RR simply plows straight ahead upon throttle-lift." I can't agree and certainly that's not what I'm feeling at all

 

[hotak]

about lift-off oversteer, have you tried with the engine braking setting in the setup? It controls how much idle gas you have to compensate for engine braking, i don't remember if you have to increase or decrease it to get more braking

 

[panjandrum]

about lift-off oversteer, have you tried with the engine braking setting in the setup? It controls how much idle gas you have to compensate for engine braking, i don't remember if you have to increase or decrease it to get more braking

OH! That is a good thought! If I'm not getting engine braking that would make a big difference. I guess I will, at some point, play around with things and see what happens. I have very little time to "fix" things that I feel should simply work out of the box.

And no, I haven't played around with diff settings. I guess, in general, I feel that sims should be setup correctly "out of the box", and not need a bunch of tweaking (besides which, there are times when, if the underlying physics are wrong, nothing will make it work correctly, making that an exercise in frustration).

I have found that if even downshift during a turn will often initiate the response I'm looking for. The only problem seems to be that it won't initiate for me in anything other than the most mild of ways when I come off throttle, even if I yank my foot all the way off at high speeds around a turn.

If I can get that resolved I'll probably love pcars. I really enjoy how the cars behave - very little room for error. For example, I find the majority sims (even AC) are far too forgiving to "throttle mashing". Not pcars; it's white knuckle and concentrate concentrate concentrate. Loving that!

I've also posted in the pcars forums asking for help. Maybe there is something in my setup that I'm not aware of making this happen, since others, including Scaff, obviously don't have the same issue.

 

[Scaff]

@panjandrum SMS are on the record as saying that they have set the cars up for mild understeer out of the box, now I have no issue with that for a race ready car (as no 'right' set-up exists here - its down to the driver and the track) but with road cars they should be set-up exactly as the road car is in reality (that however is a potential issue as well - suspension tuning does differ from market to market on some road cars).

I'm also not saying that pCars has got it 100% right either, its the blanket statement that it doesn't exist for MR/RR (and RR is a tricky one, we have two versions of one car that is RR in pCars) that I can't agree with.

Lift off-oversteer, to differing degrees most certainly exists in pCars and does so across numerous drivetrains, that this is the case would indicate that the issue is not with the core physics engine, but rather with another factor. Its also difficult to know, with the cars we have at the moment, which are right. In terms of the ones I have personal experience with they are all FF and FR, and all display around the right levels of lift off oversteer. Now if anyone has an RuF CTR3, RGT8 or F1 and a spare track I could borrow I would be more than willing to put myself forward to ive it a good test.

Given that road cars certainly seem to be the ones that are causing the most concern then it could be down to the aforementioned under steer biased tunes or the data used for the road tyres that they use, or it could be a combination of the two.

 

[mister dog]

And no, I haven't played around with diff settings. I guess, in general, I feel that sims should be setup correctly "out of the box", and not need a bunch of tweaking (besides which, there are times when, if the underlying physics are wrong, nothing will make it work correctly, making that an exercise in frustration).

Well SMS have already said it wouldn't be radical out of the box but toned down for the comfort of the masses, so you can't blame the physics engine if you don't give it a shot at least. That's a bit of a non argument there, and to be honest i doubt any sim will get it 100% right out of the box for everybody that's just impossible.

 

[panjandrum]

OK, with some help on the pcars forum and this forum I'm already getting a bit of a handle on things. I do think that maybe they've just gone for "safe" on the default tunes. I've been able to get a bit more off-throttle rotation on a couple cars already.

Does anyone know if the Brake Mapping feature also works-off throttle? It says it only works during braking, but it was suggested I reduce the Brake Mapping to reduce automatic throttle usage during all deceleration. I only had an hour or so this morning to try these things out, but my first impression is that Brake Mapping does indeed apply throttle "off throttle" and not only during braking.

Most useful so far has been adjusting front and rear sway-bars. Unfortunately, a stiffer rear mean more rotation off-throttle, and more rotation on-throttle; so the rear steps-out more easily, but it is then also harder to recover...

Changing the diff settings (unfortunately not available in all cars, what a bummer) also helped a LOT.

Thanks for your suggestions! It's already made pcars a lot more fun for me and I really appreciate the help!

 

[Scaff]

OK, with some help on the pcars forum and this forum I'm already getting a bit of a handle on things. I do think that maybe they've just gone for "safe" on the default tunes. I've been able to get a bit more off-throttle rotation on a couple cars already.

Does anyone know if the Brake Mapping feature also works-off throttle? It says it only works during braking, but it was suggested I reduce the Brake Mapping to reduce automatic throttle usage during all deceleration. I only had an hour or so this morning to try these things out, but my first impression is that Brake Mapping does indeed apply throttle "off throttle" and not only during braking.

Most useful so far has been adjusting front and rear sway-bars. Unfortunately, a stiffer rear mean more rotation off-throttle, and more rotation on-throttle; so the rear steps-out more easily, but it is then also harder to recover...

Changing the diff settings (unfortunately not available in all cars, what a bummer) also helped a LOT.

Thanks for your suggestions! It's already made pcars a lot more fun for me and I really appreciate the help!

Glad to help.

In regard to the brake mapping, yes it does seem to make a difference off throttle as well as under braking, it does seem more obvious under braking however. One thing to watch with it however, set it low (so its aggressive) and you have to make sure you match your gear to you road speed, particularly in a long braking zone with multiple downshifts. Get it wrong and you will get a lot of engine braking, potential single side lock up and a trip to the barriers.

 

[mister dog]

It refers to engine braking, so off throttle indeed (asked on the PCARS forum)

 

[panjandrum]

One problem may be that I'm not "feeling" the weight-transfer nearly as much in pcars as I would like in the wheel. I'm used to feeling exactly what the back of my car is doing, both in RL and in AC, GT6, etc. I'm not quite getting the same results with pcars. Any suggestions on FFB settings? (I know that's not directly physics related, but...) I'm using both a G25 and a T500...

 

[mister dog]

One problem may be that I'm not "feeling" the weight-transfer nearly as much in pcars as I would like in the wheel. I'm used to feeling exactly what the back of my car is doing, both in RL and in AC, GT6, etc. I'm not quite getting the same results with pcars. Any suggestions on FFB settings? (I know that's not directly physics related, but...) I'm using both a G25 and a T500...

Up the Mz slider in the car's FFB setting, helps a great deal for my wheel.


ps.I made a thread about those settings which might be helpful:
https://www.gtplanet.net/forum/threads/tune-the-cars-ffb-settings-first-setups-included.329160/

 

[K_Soze]

One problem may be that I'm not "feeling" the weight-transfer nearly as much in pcars as I would like in the wheel. I'm used to feeling exactly what the back of my car is doing, both in RL and in AC, GT6, etc. I'm not quite getting the same results with pcars. Any suggestions on FFB settings? (I know that's not directly physics related, but...) I'm using both a G25 and a T500...

It is totally physics related. When you start to lose the rear, all the car create a big torque on the tires that can be felt in the wheel.

If the pivot was exactly aligned with tires Z axis then you would only feel the Mz but as the contact patch is creating a torque because of the lever then Fx and Fy also create a torque that you can feel.

 

[Johnnypenso]

One problem may be that I'm not "feeling" the weight-transfer nearly as much in pcars as I would like in the wheel. I'm used to feeling exactly what the back of my car is doing, both in RL and in AC, GT6, etc. I'm not quite getting the same results with pcars. Any suggestions on FFB settings? (I know that's not directly physics related, but...) I'm using both a G25 and a T500...

The FFB in PCars is designed mostly around the steering rack or front end of the car. The SoP settings in the FFB menu of each car, is a way to dial in the effects that you want if the above suggestions don't give you waht you desire. The SoP or seat of the pants effect is basically transferring what is happening to the rear of the car onto the wheel, which is a sort of "canned" effect, but can be very effective of course in knowing what is happening with the rear of the car.

 

[panjandrum]

For those of you who don't know, but want to know, "what I'm bangin' on about" when I talk about Rear Engined / Rear Biased cars, I happened to watch a great Chris Harris video today, and he tells it better than I possibly can. All I can say is that, for some people (like myself) there really is nothing quite as sublime as driving an RR layout car properly. Watch the video and you'll see that he does a ton of lift-off-oversteer (he mentions the "delicious" trailing throttle at one point), and a bunch of on-throttle oversteer (I don't get to do this in my cars unless it is wet, or if I'm on dirt, snow, or ice because I don't have enough power to initiate on-throttle oversteer on a dry surface).

But watch him swing the butt of that car around both off and on throttle, using the natural rearward weight bias of that car to change attitude almost instantly. That's the joy of driving an RR platform correctly, and that's what I need, need, need to get feeling right in pcars... (If I can't get it right, I'll have to stop driving RR/MR cars in pcars just like I did GT6. GT6 has the RR dynamics so messed up that it was actually having a detrimental effect on my RL motorsports (muscle memory is a powerful thing). I quit driving RR cars in GT6 and got back into proper form by the end of last season. I won't touch anything RR in GT6 again except to check to see if a recent updated happened to fix it.)

(You can search for "polar moment of inertia" for more information about the underlying physics of why all this stuff works the way it does.)

Anyway, this is a really good video, and will give you a good idea of the handling characteristics I'm trying to achieve (in the cars which I think should exhibit at least some of these characteristics):

 

[Scaff]

@panjandrum

Any set-up tweaks you come across for the road cars please feel free to share them.

I'm fine with tuning, but I'm sure many who are not so confident would be appreciative of any tweaks and values you have.

 

[super_gt]

Anyway, this is a really good video, and will give you a good idea of the handling characteristics I'm trying to achieve (in the cars which I think should exhibit at least some of these characteristics):

And another nice video of Ariel Atom 3(Supercharged 300bhp) at Silverstone.

 

[panjandrum]

@panjandrum

Any set-up tweaks you come across for the road cars please feel free to share them.

I'm fine with tuning, but I'm sure many who are not so confident would be appreciative of any tweaks and values you have.

Honestly, I'm good at tuning in real-life, but not so great in sims. I have trouble in sims not being able to feel an entire chassis. So a small change, say to my rear-sway-bar on my 912E in RL I can feel instantly and know whether or not I like it. In ANY sim, figuring out how that same change effects things can take me hours, days, or weeks... And I don't have that much time on my hands usually.

But I'll definitely post some results if I find out anything worth-while.

 

[Johnnypenso]

For those of you who don't know, but want to know, "what I'm bangin' on about" when I talk about Rear Engined / Rear Biased cars, I happened to watch a great Chris Harris video today, and he tells it better than I possibly can. All I can say is that, for some people (like myself) there really is nothing quite as sublime as driving an RR layout car properly. Watch the video and you'll see that he does a ton of lift-off-oversteer (he mentions the "delicious" trailing throttle at one point), and a bunch of on-throttle oversteer (I don't get to do this in my cars unless it is wet, or if I'm on dirt, snow, or ice because I don't have enough power to initiate on-throttle oversteer on a dry surface).

But watch him swing the butt of that car around both off and on throttle, using the natural rearward weight bias of that car to change attitude almost instantly. That's the joy of driving an RR platform correctly, and that's what I need, need, need to get feeling right in pcars... (If I can't get it right, I'll have to stop driving RR/MR cars in pcars just like I did GT6. GT6 has the RR dynamics so messed up that it was actually having a detrimental effect on my RL motorsports (muscle memory is a powerful thing). I quit driving RR cars in GT6 and got back into proper form by the end of last season. I won't touch anything RR in GT6 again except to check to see if a recent updated happened to fix it.)

(You can search for "polar moment of inertia" for more information about the underlying physics of why all this stuff works the way it does.)

Anyway, this is a really good video, and will give you a good idea of the handling characteristics I'm trying to achieve (in the cars which I think should exhibit at least some of these characteristics):

I have briefly played around with the street version RGT-8 and can easily get it to do everything Chris Harris is doing with the exception of pure lift off oversteer on demand. Power on oversteer with massive drift like slides are easy to do, easy to just brush/tap the brakes and induce oversteer on entry as well, especially if you tweak the sway bars and other suspension components to make the car favour that behaviour. On back to back corners it's also easy to induce oversteer in the following corner just with a flick of the wheel and carry it through with the throttle. I did this on the summer tires, didn't really try the others as they seemed more suited to a track day or grip driving. I haven't tried any really unusual tuning setups though to see if it's a setup issue and/or physics. TC and stablity control were off, only ABS on as I assumed you couldn't turn it off on the real car.

The Yellowbird is a different beast to a modern supercar IMO. It was very well done in Assetto Corsa in particular and you could induce oversteer on entry just by thinking about it, but it is quite controllable and a massive amount of fun with some practice. I'm hoping PCars does it justice as well.

 

[panjandrum]

I have briefly played around with the street version RGT-8 and can easily get it to do everything Chris Harris is doing with the exception of pure lift off oversteer on demand.

The Yellowbird is a different beast to a modern supercar IMO. It was very well done in Assetto Corsa in particular and you could induce oversteer on entry just by thinking about it, but it is quite controllable and a massive amount of fun with some practice. I'm hoping PCars does it justice as well.

Yep, that's my experience too. I'm looking for that pure lift-off oversteer on-demand. I use that in RL motorsports every single time I'm in the car, so it's a bit crippling to me not to be able to induce it in pcars, at least in a few of the cars with a rear weight bias.

I agree that the YB in AC is just about as brilliantly modeled as can be. It's nearly identical to what I drive in RL, but is considerably harder to "save" once lift-off is initiated because it's so easy to get the YB's wheels to spin-up in comparison to anything I drive in RL (in mine, to transition back to understeer I can mash the go-pedal all the way to the floor as long as I'm in 2nd gear or higher and zero wheel-spin will occur, just weight-transfer back to the rear. Makes my cars WAY easier to control on-throttle than the YB would in in RL. I get to play like that in the wet, on dirt, etc. But not in the dry).

One problem I'm discovering, as I drive both pcars and AC more, is that pcars sense of weight-distribution and weight-transfer through the wheel are very reduced to any other sim I've played for any length of time. If I discover a sim that doesn't simulate that feeling, which I'm so familiar with in RL, then I invariably stop playing the sim. It's making it hard for me to figure out what's going on with the chassis because I sometimes see the car start to rotate, but don't feel it in the wheel.

I played with the Mclaren F1 and bit and actually got it to rotate quite a bit off-throttle in some situations, but the modifications I made also made it almost impossible to catch once it let go...

I'll figure it out eventually, or just give up and wait for the YB.

 

[panjandrum]

The Jack Spade tweaks have made a HUGE difference for me. I actually prefer set 4 at this point, but I will go back and try them all again when I get time. Definite increase in the feel of understeer, so that's nice, and slightly better sense of weigh-distribution and weight-transfer, so I can feel it slightly better when the back starts to step out just a bit.

For those of you with PCs (or the patience to edit the settings yourself manually), I highly recommend them!

 

[carlosy]

Regarding the RUF RGT-8, just put on UHP tyres, raise pressure to max (at least on the rear) and make the rear stiffer.

 

[panjandrum]

Regarding the RUF RGT-8, just put on UHP tyres, raise pressure to max (at least on the rear) and make the rear stiffer.

Yeah, but unfortunately that doesn't really cover it, because that causes more off-throttle oversteer AND more on-throttle, making it hard to catch when you get back on-throttle. So it's not really a complete solution as what you end up with then is a car that's hard to control. (You should see how far I can adjust the handling in my 912E based solely upon the rear-sway-bar setting. And that's an adjustable model, I don't even have to move to a heavier sway-bar. I can go anywhere from "nice and neutral on-throttle" to "all oversteer all the time" just by sliding the adjusters 3"). You do NOT want an RR car to easily rotate on-throttle, unless you are a professional drifter. You want them to transition back to mild understeer as you squeeze the trigger down. Anyway, I'm not going to pursue it much further until a chassis I actually drive in RL motorsports becomes available in Pcars. It's a very fun product, no doubt.

 

[UkHardcore23]

The Jack Spade tweaks have made a HUGE difference for me. I actually prefer set 4 at this point, but I will go back and try them all again when I get time. Definite increase in the feel of understeer, so that's nice, and slightly better sense of weigh-distribution and weight-transfer, so I can feel it slightly better when the back starts to step out just a bit.

For those of you with PCs (or the patience to edit the settings yourself manually), I highly recommend them!

Your using the bumpy settings?

 

[KSaiyu]

So I was just testing the RGT vs the 1 series to investigate the problem with RR modelling and I noticed something odd: I couldn't spin out from a donut. They are stupidly easy to control in both cars and it's virtually impossible to over-rotate it beyond the point of capture. I tried the Formula A and found the same thing. I thought it might be the game auto-clutching to "save it" for me but even with auto-clutch off it was still way too easy.

Anyone else noticed this?

 

[NLxAROSA]

Did you try with the UHP Summer tires instead of the default grippy tires?

 

[KSaiyu]

Will try tomorrow, but surely you should be able to on normal

 

[Scaff]

Will try tomorrow, but surely you should be able to on normal

Sorry but its not 100% clear - what are you having trouble doing?

Maybe a video would help?

 

[Johnnypenso]

Will try tomorrow, but surely you should be able to on normal

Default tunes are very safe. I did try light tuning and summer tires on the RGT-8 and didn't get lift -off oversteer but could induce oversteer with very light braking and easily with the throttle.