Tire Thermal Degradation. Does it work ?

We had a 1000km race in modded Brianza (1966 version with chicanes). After finishing my solo drive in 5hours endurance race, I have to say that tires performance remained much better than I have anticipated. I did drive a car that is less hard on tires, and I also put effort to save them. Although I spent on average at least 4-6degrees above tire heat degradation activation temp. This would make total heat history 18000s*4deg=72 000, a step value on those tires is set to 6850, so in total at least 10 degradation steps would have been taken, which should have resulted in about 3% of grip loss. I think it is fair to say that it should have perceivable difference on car handling and laptimes. But I was able to drive just as fast, apart fuel saving.

As I still had doubts about thermal degradation working/not working, I attempted to do some tests in devmode with extreme values. Unfortunately I haven't seen specific indicator available for thermal degradation, just usual abrasive wear. I set degradation history step to be just one degree, and just for rear tires. And went out for several laps beign rough on rear tires, and I couldn't tell a difference in 3-4laps, while I should have had more than 7% of grip loss within first lap or two.

I want to ask, am I doing something wrong, looking at some wrong thing ? Maybe I don't understand how it works ? I suppose tire bristle temperature is equal to tire surface temperature ? Does it work ?

Code:

DegradationCurveParameters = (<activation_temperature_K>,<heat_history_step_Ks>) where heat
history is essentially a linear progression of temperature over activation point multiplied by time. i.e.
if the tyre bristle is 30 degrees over the activation temperature, for 30 seconds, the result is a heat
history of 900 Ks

 

In short, yes it works.
If you've ever driven any official GT3 car (before the updated tyre model) you could see how the thermal deg was so aggressive that it just killed the tyre performance after 1-3 laps. Abrasion wear is generally not causing any grip loss until you reach the very end of the %, or if the physical tread becomes too thin. Grip loss from abrasion wear can of course vary from content to content, but from what I've noticed all official content follows the same pattern.

Thermal deg isn't shown anywhere, so the easiest thing to do is implement the calculation into MoTeC so you can visualize and follow the thermal steps. If you have the tyre physics file you can set it up and test some extreme grip loss values.

The only thoughts I've had regarding the thermal deg is which layer it reads from. Surface, rubber, or carcass -- but now when I see the explanation involving tyre bristle it has to be something dynamic. Whether it would follow surface temp with 100% accuracy I don't know as some heat from the bristle surely has to be distributed to other areas?

 

It doesn't help that it is not possible to take a look at official cars physics.

Yes there are some questions to be asked. I wonder if temperature readouts seen in garage menu is actual core temps, because to me it is a bit suspicious, those could be just surface temps frozen from the last moments before escaping the track. That window is a bit wonky anyway, it shows tire loads as Kg, but annotated as N.

It is not impossible that due to something my own tires just stays relatively cool at the core, and I just don't know. I like how they works though, driving is nice. Also I wonder if there are several thermal layers in physics, or just surface and core.

Maybe these params are also in effect for thermal deg, I mean non directly they surely are because they affect fluctuations, how quickly tire gets hot and hotw quickly cools off. But perhaps directly it also somehow accounts to thermal deg.

Code:

ThermalDepthAtSurface = The depth of the temperature sample layer used for contact properties
(i.e. grip and wear); if provisional second layer is disabled, tread will never be allowed to get thinner
than this value. Not recommended to push below the default value of 0.0001, as the accuracy of the
thermal conduction may suffer. Higher values will reduce temperature fluctuations felt in tyre
surface temperatures which are used for contact properties. Lower values would increase the
conductance, increasing fluctuations but as stated may create accuracy problems if the rate of
conductance is too quick for the physics sampling rate.

ThermalDepthBelowSurface = (if provisional code enabled) the depth of the second layer; value
should be >= surface layer but not too big; tread will never be allowed to get thinner than these two
layers.

edit:
It seems like it could be indeed that garage shows surface temps. It could be coincidence from my single check, but it appears that average of IMO temperatures from garage screen fits temperature readout of tire hud in game. I used to think that game hud shows max temp point of tire... So, no way to know core temps ?

 

You can see a pattern in the official cars. You generally have good grip for the first 1-3 laps, then you lose a big chunk of time, and then another, and another. After that drop-off, it stabilizes. This points towards aggressive thermal drop-off in the first steps and then a more linear reduction that's so small that the reduced mass from less fuel is beneficial to lap time.

The carcass and rubber temp will be quite a bit hotter than the surface, and much, much less dynamic. You can't affect the bulk temp that much from driving, which is where I slightly disagree with the game as I feel there should be some point where you drive too hard and overheat the bulk, and have to drive smoother/slower to regain the grip. Then again, the whole thermodynamics model seems to be a bit wonky in rF2.

Just use MoTeC and DAMPlugin for tyre temps, mate. There you get three measuring points on the surface, rubber, and a single measuring point of the carcass.

I think ThermalDepthAtSurface, ThermalDepthBelowSurface will affect temps slightly, but not by a lot. I've played around with them a bit but I didn't see or feel a lot of difference in the data. I would guess that the largest difference will be from the physical tread wear.

 

The garage has always shown the surface temps, and the HUD has always been the average*. And I am sometimes surprised by things you say given your history of car modding.

*in rF2 I think the HUD temp at least may be weighted towards the contact patch, as if you do a good lockup and then drive slowly you can see the temps fluctuating

 

Thank you for confirming that this detail is true.

Yes, I still have many things to learn, from most basic like what tire temps are shown in garage menu, to how thermal degradation actually works in rF2, and if it does.