Group A Classic DTM tire model issue?

So we started racing the classic DTM series in our private league post V1.6.3 and we've perhaps notice maybe a few quirks with the BMW and Merc tire?

Most of the drivers racing the BMW and Merc have noticed the cars don't like any rear slip angle once the tires warm up get into their operating window (green). There have been several cases where people are suddenly/randomly losing the rear end when the tires are still green and not over heated (yellow). As soon as a slide starts with the BMW or Merc there is no saving it with these cars. The slides aren't starting because people are making sudden inputs and are shocking the rear tires causing it to lose traction. Alot of times they are smoothly and gradually getting on the gas at the limit as the slides start and no amount of throttle or steering modulation can save these slow lazy spins. Most of these guys are currently top 10 on the Nurburgring GP Veedol leaderboard, so they know how to drive. They also happen to be really talented drivers IRL that I know personally. Some were saying this feels like an iRacing tire model.

We have noticed when the tires are cold (blue), they are more forgiving. They get load on them, slide and build up heat. Then as they are building heat they turn light green. In the light green state, the cars are faster and easy to drive. They can be aggressively driven with some amount of yaw when light green. Once they turn green (fully warmed up) then we see this odd behaviour with the tires, usually 3-4 laps in, where you will get these lazy unrecoverable spins. I would expect this sort of behaviour to happen if the tire got overheated and they turn yellow. By the way we also tested them as they got overheated (yellow), it was like driving on ice.

Having driven grippy R-compounds in real life, you usually can drive them with some amount of yaw and modulate the amount of yaw with the throttle. Over do it and you'll pay the price obviously. But it feels like with both the BMW and Merc, once they tires get into their operating temperatures they don't like to be driven with any yaw or you risk a very sudden unrecoverable spin. That being said, I haven't driven these cars IRL and they might be just as treacherous as protrayed in AMS2. Or perhaps the type of tires used on those car did not have a progressive break away characteristic and we more "snappy" at the limit. :shrug:

I understand different tires IRL have different behaviour at the limit as I have experienced that 1st hand. Some tolerate more yaw than others, some are progressive in their break away characteristics, some are more snappy and offer a smaller window to catch the car. I don't consider the BMW or Merc to be high HP cars or car with a lot of aero grip. Which means most of the grip is mechanically generated, which to me also means the loss of traction shouldn't be so sudden and more progressive. So in my head driving these cars at the limit shouldn't be this difficult if you setup your car to be looser. Or maybe I'm wrong and maybe these car are a deadtrap IRL?

Anyway, this has totally also changed my tuning direction with these cars, as it seems setting up these 2 cars to be looser or neutral handling on corner entry and midcorner is just asking for trouble during the middle of a race. And yes I know some folks are going to say you can keep these cars under control if you are super careful and very smooth but that is also very slow and not how I would picture you would race these chassis. Sorry for the long post and thanks for taking the time to read it. Thoughts?

 

I am nowhere those guys in term of pace and never will pretend to be, but I have all my setups on the lazy understeery side for that reason, otherwise you will get that sudden rear loss (that can't be foreseen nor saved) since 1.6. It is less noticeable on modern GT or on formula cars due to the downforce making its thing, but still you will get those sudden grip loss from time to time with a conventional or more overtseery setup. Just jump in random lobbys to convince yourself and see lots of folks just spinning out (they can't all just be "bad", right ?). Most folks will probably tell you this is not an engine problem but a personal skill issue, make what you want of it.

 

I watched some LFM Classic DTM youtube videos when it was beta last year and it did seem like people driving the BMW and Merc were constantly spinning out. So I'm not surprised. It's probably why LFM doesn't host the Classic DTM series anymore. :shrug:

That being said, with V1.5 it was less of an issue and you could drive the cars with a lot of yaw. It's the same Madness physic engine, so I'm guessing some of the parameters defining the tire carcass probably changed enough where the tires have become a bit unpredictable at the limit. It just seems it went a little bit overboard with the Merc and BMW. Only the Devs would truly know. I just hope they get a chance to read this and investigate a bit.

The folks who like to point out a skills issue are usually trolling on Reddit. Luckily this forum is a lot more civilized and helpful. People here are also more receptive to genuine critiques and concerns. I've been visiting these forums long enough to know that.

 

I am not versed in car setups but noticed that issue for that sudden spins for the hotcar fusca. Easily reproducable on taruma on the fast turn after the finish line. I tried to find a fix through the setup but was not able to.

 

its a Swing axle car . they aren’t easy .
if you are unfamiliar with them and what what that means , it’s a great time to do some googling and follow the path of education about cars that Ams2 can lead too.

 

I know that they are difficult to drive and love to drive them to the limit in AMS1 but in AMS2 something makes them undrivable for me which fits the explanation of the issue here.

 

It could be an issue of HUD calibration showing wrong colours, and tyres being actually overheating when they are full green. It would require numbers and some knowledge of working temperature range of the real life tyres to get this out of the way and find the root cause.

 

Yea I thought that too initially, but it's definitely not a tempurature range color issue. The way you overheat a tire is if you "shock" them harder while driving and put a lot of load through them suddenly. The smoother you are the more load you can get away with and the slower the traction loss starts to happen. This also has the benefit of not adversely wearing or overheating them.

The current problem is this behaviour is happening even when the car is being driven smoothly without shocking the tires, but gradually putting load on them through a corner and they start a lazy slide that is basically unrecoverable giving you no window to catch the slide. That IMHO, is unrealistic. From the sound of things, it's impacting other cars too like the Copa Fusca which is basically a VW Beetle from the 60s and 70s. If anyone has driven one of those cars IRL, they are low HP fun little cars you can toss around and drive hard.

 

Understood. Tbh I raced the M3 and 190E at a couple different tracks and race lengths (between 15 and 30 minutes) and never found said issues. If you could please specify a combo with exact conditions where this problem is exposed more clearly, I'm willing to give it a go.

 

Fusca 1 Hot Cars on Taruma. Happens when entering T1 that the rears unaturally oversteer way to much. On AMS1 it is not like and you can push it a lot better on the limit, while it is still difficult to drive.

 

ok . I tried this combo, and it’s indeed very tricky .
Not as a remember it driving last time I tried it at some point during Beta .
It almost feels like there’s no engine braking acting on the drive line or something else mechanical effecting the car adversely. , and maybe it’s just my mind playing tricks on me , but it kinda feels to be easier to unsettle the car turning left more than right …

I don’t find it underivable, but it takes very precise inputs and a little patience to be able to get confident with . Not a car that can be abused and mistreated while staying on track .

 

Also tried it yesterday, and found that holding always a bit of throttle make it way more manageable. Not necessarily due to engine braking, maybe also the diff overracting on coast and well the suspension type is not helping either with that. Regardless, in that case I do not think we are looking at a tyre model issue, unlike what has been hinted at for the GrA cars.

 

Maintenance throttle has always been important in this type of car , and delayed downshifting . But it’s not having as much impact as it should .

 

On AMS1 I manage to push the car to 1:16 lap times and the car never spin out on T1 as it does on AMS2. Its a very stange behaivor I even dont feel when then rear starts to come out and its quite impossible to catch/counter it with pedal applicaiton/steering.
(Both on timetrail mode)

But it might be another issue not connected to the initial poster issue. Sorry if that is the case.

 

Thanks, it's the BMW or Mrec at Jacarepagua 2005 in the following conditions with the following setup running lap times in the mid 1:58s to low 1:59s, Mostly happens on turn 6 or the final turn as you get on the gas coming out of the corner.

Using the following setup.




Thanks for looking into it.

 

The setup? The laptimes? Or the throttle application? lol
Either way, thanks for looking into it.

 

To help dial in some understeer and improve stability while trail braking under corner entry.