BMW M4 Class 1 2021

AMillward said:
Class 1 has waaaay more aero on tap than a GT3, a BTCC or a V8 Supercar and they run stupid low to the ground, as well as being pretty stiff to keep the ride heights stable with the downforce. So going over kerbs is going to mess around with balance, cause grounding and all sorts.

Same way you won’t find an f1 car able to take the sorts of kerb attack that a GT can, because it’s too reliant on aero than mechanical.

see here: not using a lot of kerb. GT3 would be using more of the green stuff that’s a bit higher.
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Pressing issue?
 
Sim_Player said:
When they apply newer tyre knowledge to GT content it would make them little bit more nervous over curbs , bumps etc.(hopefully)
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Not sure what they changed on this BMW tyre model settings, but I find it a improvement in realism.
Hopefully this knowledge can be transferred successfully to other cars.
 
Filip said:
Aren't same tyres used in entire claas, not just BMW?
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This BMW is in a class of its own actually >DTM.
And not according 2021 DTM regulations, which is Simular to GT3 from what I picked up.
Watch the release presentation with the BMW representative.
 
EricW said:
This BMW is in a class of its own actually >DTM.
And not according 2021 DTM regulations, which is Simular to GT3 from what I picked up.
Watch the release presentation with the BMW representative.
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BMW have been also developing a GT3 variant of the same car. I SUSPECT that will be a DLC item at some point. The real car was supposed to have had it's first race this past weekend, but there was a component failure during practice that caused a crash, so the car was withdrawn. Hopefully we'll see the GT3 M4 at one of the new few NLS rounds at the Ring.
 
So first: I have no idea whether the tires on this car are "more realistic" than any other tires on rF2 cars.
Second: I can say I am pretty disappointed in the tires on this car overall, and I'll try to explain why.

The car is extremely stiff. A DTM Class 1 car is an aero car, and so I can understand that. But this feels extreme. And thus, its probably not a good platform to see how tires can be adapted via vehicle dynamicists, to give different results based on the style of driving. The default car setup is extremely stiff in roll both front and rear. It's very sensitive and spins up the rears out of slow corners (where there is little aero impact) and coming off the pit speed limiter. I've tried the car at Nurb GP and Spa. Its terrible at Nurb in just about very slower corner, and in fact, most corners. Its better at Spa. But I basically had to take ARB to 2 up front and 1 in rear to make it any any way shape or form drivable.
You can watch the temps on the in-car display and also look at inner/middle/outer in the setup screens. Having the car that stiff, it slides everywhere, and that makes the tire temps shoot up: I'd had them above 200 and even 240 with the camber settings both front and rear with the stiff setup, and that's without spins. With the ARBs changed, I can make it vary from 140 to 180, and at 180, it'll still grip. Driving in a straight line, you can watch the temps plummet. Now, I feel this is possibly much more accurate to real life, and certainly better than iRacing where once you've got temps up, they never seem to cool down (both surface and core temps). In iRacing once you've fried the tires, they stay fried for a long time, and any attempt to drive at reasonable speeds (i.e. 80% of full effort), they just go back to blancmange again. It's become a bit better over time, but is still way wrong - in real life, you can watch people do spin turns with clouds of smoke and 2 turns later they are back on full throttle charge.

This car has lots in common with the Porsche Cup: way too stiff, and frankly, no joy at all to drive. Changing the stiffness helps (enduro versions of Cup car) but the tradeoffs that should bring, don't seem to ever occur. My personal feeling is, where in general the 'normal' tire model is too forgiving in the GT3 cars, this one is too far the other way. There's very little saving this tire once its gone, you're going to spin - it doesn't seem to generate long slides and then come back. It's there - it's there - it's there - it's not there. Maybe this has eliminated the crazy levels of steering input done by aliens, fixing the fronts, but its now caused more of a problem at the rear on both entry and longer turns like you get several of at Spa.

In my opinion: more work to do. Maybe the tire will work on the other GT cars, but I'm doubting it. But I can add this car to the "not using it" list like the PCup.
 
burgesjl said:
There's very little saving this tire once its gone, you're going to spin - it doesn't seem to generate long slides and then come back. It's there - it's there - it's there - it's not there.
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That sounds kind of realistic for this kind of tire and car. And still not quite true, I have had lots of really big slides with this car that I didn't end spinning out, usually loosing momentum and pace, but few times didn't even loose pace. The only "undrivable" moments I have had was turning on DRS at bad moments.

burgesjl said:
My personal feeling is, where in general the 'normal' tire model is too forgiving in the GT3 cars, this one is too far the other way. There's very little saving this tire once its gone, you're going to spin - it doesn't seem to generate long slides and then come back. It's there - it's there - it's there - it's not there. Maybe this has eliminated the crazy levels of steering input done by aliens, fixing the fronts, but its now caused more of a problem at the rear on both entry and longer turns like you get several of at Spa.

In my opinion: more work to do. Maybe the tire will work on the other GT cars, but I'm doubting it. But I can add this car to the "not using it" list like the PCup.
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This is why this tire logic probably isn't going to fly, doesn't matter if it is realistic (in my opinion it is), there will be lots of people like you, who just aren't going to adapt to it. It is more challenging to drive... thats it, end of story. It would be simply too good if most simracers likes would meet ideally at the same spot where optimal realism is at, but reality is not optimal, it is just how it is. Although car itself is way more challenging too than what is usual, and you are right, it has hell of a stiffness to it, and I would also guess that tire is too slippery, it should perhaps grip harder mechanically. But guess what, it wouldn't make the car any more forgiving, it wouldn't become easier, more driftable and predictable at slides. It would be the opposite, you'd go higher up at performance, and the cut off and drop off over the limit would be more brutal, which sounds to be too brutal to you already as it is. Although IMO you are right car is probably (by default setup) too stiff for how the tires are. I suppose the stiffness of a car is probably realistic, and probably stiffness of tires doesn't match it up and is too low, at least in anything except high rubbered road conditions.

But wake up, if you want a car that is ok with long slides and still can come back smoothly, then you'd probably be better with cars that aren't on slicks and doesn't have lots of downforce. I see there are lots of people around who wants to imitate racing modern high performance race cars, but what they need in their mind are either road cars or classic cars which are the ones that should be alright with big slides and have much lesser natural frequency (i.e. wouldn't demand as much fast and precise driver reactions). But people want everything in one thing: mix of positives of modern race car and road car with drawbacks of either removed, and thats how you get realism of level of ACC.
 
OK, let me try again.

I suspect this car SHOULD have a very stiff setup; because it is very aero dependent. That means you need a stable platform - you can't have ride heights getting changed under braking/acceleration and probably just as important under roll. So the tire should work well with stiff ARBs but - it doesn't. It's constantly sliding, and the temps shoot through the roof. Which will cause a spin eventually. The solution - go softer in roll - should have deleterious effects on aero platform, but yet, there don't appear to be any. The car now grips under normal circumstances with less ARB. But its like there's some sort of temperature cliff: go over it, suddenly the grip is gone. It feels like the tires themselves, there's no actual give in the sidewall or compliance to the road surface - they are rocks, or at least, wood. The tires on a regular GT racer will be designed to be very forgiving, because a lot of the time it will be driven by gentlemen drivers who just can't deal with it (GT3 especially, less so on GTE but there are still AMs racing those). I'm suspecting that, in this race car like in F1, the sidewalls provide a lot of the give, so that the car is not completely binary in its grip/no grip. Don't know, because I don't watch DTM.

To explain further: one of the problems I've always had with sim racing tires especially on iRacing is, they don't seem to adhere to the rules of the traction circle. That is, there is both longitudinal and lateral grip, the total amount of grip is on a "circle" from those two. But I see people who are sliding - have exceeded lateral grip - but yet they are still able to add throttle and drive forward faster, and get better lap times. That shouldn't be possible. The tires seem to be a bit better under braking (into corners) than on acceleration (mid to corner exit). Hence, people floor the throttle and the car drives away even though its already sliding sideways. (I also believe the sim makers believe peak grip happens at way greater slip angles than it actually does, which is due to the sidewalls and carcass flexing and not due to actual slip angle of the rubber itself - so we end up with slip angles of 12 deg still being fast, on a real car 8 deg and you'd be over). So in this specific car, I can be in a longer corner (lots of these at Spa) and maintaining throttle, not adding it or sliding sideways, and suddenly the car will slide. Not a huge amount, but some. I don't believe it should, and the reason is the temps are rising too fast or the grip curve too abrupt. So, my reading of the tires is that they both are heating up and cooling down too fast, and that's why I'm seeing issues in longer corners. I also believe they have tried to "fix" the fronts problem, but in doing so they've made it very susceptible at the rear, again to large temp increases where they shouldn't be happening, under initial turn in. Maybe you can fix that with setup. But now you've got heat in the rears due to that instability, trying to maintain constant throttle, they go over.

So my point in all this is: the tire may be realistic (i.e. correlating to real world data) on this type of car. But we'd been told this was a "new tire model", with the implication that whatever approach had been taken with these, would be applied to the other cars. I'm praying this won't happen, because the same approach on the GT cars would make them equally as unforgiving, which isn't how they are.

BTW, I run on iRacing typically the IndyCar, a downforce single seater, and the LMP2, also a very aero car. I'm not a fan of their GT cars; so I'd like a good GT car experience on rF2. In general I've always been better in downforce cars, also on ISI sims; and largely because I suspect the extra downforce masks some of my poor technique, but still, I'm able to push hard to get laptimes; though with iRacing, there's always a bit of a sense of you've got to baby it a bit. There have been times with the IndyCar on iRacing that its also been very binary, lateral grip or not, and this feels like those times with this car. Finally, I always used to enjoy the CART mods on rF1 because you could push like hell to get a laptime from the car, wring its neck, which is what I think the drivers have to do in real life. In all sims since, I've not been able to replicate that because the tires are too sensitive, so you end up having to be very precise.
 
Kahel said:
That's true... but it's not wrong to say that rf2 content like gt3, gte and even lmp are too forgiving on curbs and pretty much without consequence even on long endurance...

So, an area where the sim could use some work.
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I don't agree.
We ran the VEC 24 hrs of LeMans as well as the Sebring, Suzuka and Spa events in the 911 GTE. Kerbs were deadly. More deadly than real life kerbs.
 
burgesjl said:
So first: I have no idea whether the tires on this car are "more realistic" than any other tires on rF2 cars.
Second: I can say I am pretty disappointed in the tires on this car overall, and I'll try to explain why.

The car is extremely stiff. A DTM Class 1 car is an aero car, and so I can understand that. But this feels extreme. And thus, its probably not a good platform to see how tires can be adapted via vehicle dynamicists, to give different results based on the style of driving. The default car setup is extremely stiff in roll both front and rear. It's very sensitive and spins up the rears out of slow corners (where there is little aero impact) and coming off the pit speed limiter. I've tried the car at Nurb GP and Spa. Its terrible at Nurb in just about very slower corner, and in fact, most corners. Its better at Spa. But I basically had to take ARB to 2 up front and 1 in rear to make it any any way shape or form drivable.
You can watch the temps on the in-car display and also look at inner/middle/outer in the setup screens. Having the car that stiff, it slides everywhere, and that makes the tire temps shoot up: I'd had them above 200 and even 240 with the camber settings both front and rear with the stiff setup, and that's without spins. With the ARBs changed, I can make it vary from 140 to 180, and at 180, it'll still grip. Driving in a straight line, you can watch the temps plummet. Now, I feel this is possibly much more accurate to real life, and certainly better than iRacing where once you've got temps up, they never seem to cool down (both surface and core temps). In iRacing once you've fried the tires, they stay fried for a long time, and any attempt to drive at reasonable speeds (i.e. 80% of full effort), they just go back to blancmange again. It's become a bit better over time, but is still way wrong - in real life, you can watch people do spin turns with clouds of smoke and 2 turns later they are back on full throttle charge.

This car has lots in common with the Porsche Cup: way too stiff, and frankly, no joy at all to drive. Changing the stiffness helps (enduro versions of Cup car) but the tradeoffs that should bring, don't seem to ever occur. My personal feeling is, where in general the 'normal' tire model is too forgiving in the GT3 cars, this one is too far the other way. There's very little saving this tire once its gone, you're going to spin - it doesn't seem to generate long slides and then come back. It's there - it's there - it's there - it's not there. Maybe this has eliminated the crazy levels of steering input done by aliens, fixing the fronts, but its now caused more of a problem at the rear on both entry and longer turns like you get several of at Spa.

In my opinion: more work to do. Maybe the tire will work on the other GT cars, but I'm doubting it. But I can add this car to the "not using it" list like the PCup.
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Agree with what you wrote about this BMW... you need to drive it like a sunday drive, if you push it he will kill you, i had a bad experience with it aswell! In relation to the Porsche Cup i don't agree, it is a great car to drive IMO...
 
burgesjl said:
But I see people who are sliding - have exceeded lateral grip - but yet they are still able to add throttle and drive forward faster, and get better lap times. That shouldn't be possible.
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I have thought this for a long time. During a slide in rF2, the rear tires have massive longitudinal grip. Floor the throttle mid slide and you get immense forward thrust. This makes it a) harder to drift than it actually is in real life and b) gives you the ability to set fast lap times because exessive slip angle and wheelspin is not punished by losing forward momentum.

Back in the day this is why I found it hard to drift, it was very difficult to keep the rear tires "lit up" through the entire slide, you would need to work the throttle and steering extrememly hard and have perfect amount of momentum to keep the rear tire spinning.

Once the rear tires have exeeded a certain slip angle, the throttle pedal should respond almost as if the car was in neutral - almost reving freely as the rear tires spin with minimal resistance. In my mind, this lack of "rear tires spinning freely once sliding" is one of the fakest things abour rF2. I honestly can't believe that more people aren't talking about it. But I cannot say it's wrong definitively, because maybe on a grippy track, with slicks things are different etc.

Some years ago I made a video using three different cars showing that I think the rear tires have too much "push" when they are spinning. I have a pretty low power car IRL and I can easily do a brakey and the car stays in one place, the grip of the front tires easily overcoming any push from the rears. I have seen many cars do "brakeys" IRL... like, it is not some mystical thing that is hard to achieve. It's a good simple test IMO. But again, with different cars such as the ones shown, I can not be 100% sure because I have never driven them.

 
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This BMW M4 Class 1 is not a GT3 / GTE, there are a few differences between them. To have a reference context: https://www.windingroad.com/articles/reviews/class-one-new-regulations-to-combine-dtm-and-super-gt/ or https://en.wikipedia.org/wiki/Class_One_Touring_Cars
In my opinion it is a car that was born dead and was left in limbo. Aston M, Audi and 3 other Japanese brands also prepared their own Class 1; The idea was to merge the DTMs with the Japanese SuperGTs, but in the end the journey did not come to fruition, I don't know if because of the pandemic, the little interest (at different levels) of the brands involved or some other reason, or all together. ..
These cars began to be designed in 2014, they were not developed or raced for years, as S397 states in its announcement, they only competed 2 seasons, and in the 2nd season only Audi and BMW competed (the 2 seasons were won by Audi). The technical specifications they provide are not very detailed either, what do I care about the measurements of the brakes? = Nothing..., give me the optimal working temperatures, for example ... comparing with a GT3 is illusory. A GT3 weighs at least 240 kg more and has about 100 hp less, I think that this BMW has 19 front and 20 rear wheels, a GT3 has 20 front and 21 rear wheels and the rear ones are wider.
I suppose that due to licenses, contracts and commercial agreements in DTM they ran with Hankook and this Class 1 had signed an agreement to continue using this brand, I suppose, but by changing this year DTM to GT3 (with ABS), they have changed to Michelin; the only question was which tire to use for the whole season, S7, S8 or S9?: https://www.motorsport.com/dtm/news/single-michelin-medium-tyre-gt3-cars/6506631/?nrt=45
I think that in the vast majority of GT3 championships they use Michelin, the Blackpain I think runs with Pirelli, with new GT3-specific tires (they have also released a new GT4-specific model), and I don't know if other brands are used in GT3 championships. Dunlop? I think I've seen Michelin and Bridgestone tires on SuperGT? ... but pretending that other cars in RF2 ride these "Hankook" tires is, in my opinion, ridiculous
As this is a simulation, I could test this car with GT3 or GTE tires ?, or try Hankook tires on GT3 / GTE ?, but I'm afraid "officially" this will never be possible.
As long as there are no other rivals in its class this car stays for one-make cups, although I suppose it could also be used in fictional multiclass races.
As for the new tire model for this car ??????? !!!, will it be the same model as always, with other sizes and with different parameters of: wear, temperatures, grip, slip, etc ... ??. Don't sell me smoke ...
For those who ask about DRS: Drivers can activate it a total of 12 laps when they are 3 seconds behind the driver in front (and not 1 second, as before); In the last 5 laps, it can be used by all drivers except the leader, regardless of the distance between the cars. (2019). The DTM cars also have limited fuel consumption (95 kg / hour) for a 55 minute + 1 lap race, and make a pit stop to change tires.
I tested the car for 3 days with a friend on various circuits and I don't think I need to worry about burning the engine due to the temperatures.
 
green serpent said:
I have thought this for a long time. During a slide in rF2, the rear tires have massive longitudinal grip. Floor the throttle mid slide and you get immense forward thrust. This makes it a) harder to drift than it actually is in real life and b) gives you the ability to set fast lap times because exessive slip angle and wheelspin is not punished by losing forward momentum.

Back in the day this is why I found it hard to drift, it was very difficult to keep the rear tires "lit up" through the entire slide, you would need to work the throttle and steering extrememly hard and have perfect amount of momentum to keep the rear tire spinning.

Once the rear tires have exeeded a certain slip angle, the throttle pedal should respond almost as if the car was in neutral - almost reving freely as the rear tires spin with minimal resistance. In my mind, this lack of "rear tires spinning freely once sliding" is one of the fakest things abour rF2. I honestly can't believe that more people aren't talking about it. But I cannot say it's wrong definitively, because maybe on a grippy track, with slicks things are different etc.

Some years ago I made a video using three different cars showing that I think the rear tires have too much "push" when they are spinning. I have a pretty low power car IRL and I can easily do a brakey and the car stays in one place, the grip of the front tires easily overcoming any push from the rears. I have seen many cars do "brakeys" IRL... like, it is not some mystical thing that is hard to achieve. It's a good simple test IMO. But again, with different cars such as the ones shown, I can not be 100% sure because I have never driven them.

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Well, this definelty tied to the way alien drive faster, so if right it should be given more awareness.
 
green serpent said:
I have thought this for a long time. During a slide in rF2, the rear tires have massive longitudinal grip. Floor the throttle mid slide and you get immense forward thrust. This makes it a) harder to drift than it actually is in real life and b) gives you the ability to set fast lap times because exessive slip angle and wheelspin is not punished by losing forward momentum.

Back in the day this is why I found it hard to drift, it was very difficult to keep the rear tires "lit up" through the entire slide, you would need to work the throttle and steering extrememly hard and have perfect amount of momentum to keep the rear tire spinning.

Once the rear tires have exeeded a certain slip angle, the throttle pedal should respond almost as if the car was in neutral - almost reving freely as the rear tires spin with minimal resistance. In my mind, this lack of "rear tires spinning freely once sliding" is one of the fakest things abour rF2. I honestly can't believe that more people aren't talking about it. But I cannot say it's wrong definitively, because maybe on a grippy track, with slicks things are different etc.

Some years ago I made a video using three different cars showing that I think the rear tires have too much "push" when they are spinning. I have a pretty low power car IRL and I can easily do a brakey and the car stays in one place, the grip of the front tires easily overcoming any push from the rears. I have seen many cars do "brakeys" IRL... like, it is not some mystical thing that is hard to achieve. It's a good simple test IMO. But again, with different cars such as the ones shown, I can not be 100% sure because I have never driven them.

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Thats interesting. I bet it could be tweaked out by manipulating three things: sliding friction coefficient, friction loss due to heat and abrasive tire wear. Some of these must be too good to have tires capable of this propulsion eve nwith such a massive wheelspin for such a massive long time with front brakes totally locking the front wheels. I assume it is most likely either too low abrasive wear at very high temps, or too low grip drop due to such high temps or combination of two. All of these are real time parameters of the tires.
 
mantasisg said:
Thats interesting. I bet it could be tweaked out by manipulating three things: sliding friction coefficient, friction loss due to heat and abrasive tire wear. Some of these must be too good to have tires capable of this propulsion eve nwith such a massive wheelspin for such a massive long time with front brakes totally locking the front wheels. I assume it is most likely either too low abrasive wear at very high temps, or too low grip drop due to such high temps or combination of two. All of these are real time parameters of the tires.
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One should do some tests with some of the S397 cars and see if this also happens. If you think about how aliens drive the cars with crazy understeer inducing and then using throtle to rotate the car while rears are on the edge or already sliding, goes a long way to explain why the car doesn't get out of control much more easily when it seems one has the benefits of a AWD rally car "pushing" the car forward to get out of a drift... and this with a RWD car.
 
Yes, interesting would be to try this with the new BMW.

I know I'll try it with cars I am doing too :D We need more physics evaluation tests like this. Would be great idea to get more of test like these and compile and document them. Worth noticing that tires, surfaces and cars themselves are all different and probably different results should be expected.

Older bias ply tires or some hard compound street tires could possibly keep more grip at such wild grip, than some semislicks that are oriented at much smaller performance window:

Wonder what tires are these:

I watched some more burnout videos, didn't see one with front wheel locked and car still pushing it while performing a burnout. I'd be interested to see one like that, it might as well don't exist, unless front wheels are on bananas.

I think it is simply down to fact that sliding friction is lower than static friction, and it only will go lower as tire overheats. On top of that even more so if it car has more load on front wheels, then it has more grip there to begin with. On the other hand if tires has some aggressive thread and hard rubber, and tarmac is rough, there might be a lot of mechanical keying that will work like perpendicular surfaces to launch tire forward, but then again these could accelerate tire shredding dramatically.
 
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