The Problem with Assetto Corsa’s Tire Model

If you have been around the Sim Racing world for a while, you have no doubt heard of the term “Tire Model”. The Tire Model is essentially the system that a Sim Racing title’s developer will employ to simulate tire dynamics, such as flex, torsion, grip, and also tires going flat or blowing out.

Many Sim developers will invest countless hours, trying to ensure that their tire model is the most realistic, due to the fact that tires and wear is a major factor in the real world. They tend to be one of the more publicized elements of Sim Racing titles, because of the sheer importance. However, it’s a tricky situation to get a tire model right, and sometimes there are portions of a tire model that falls through the cracks.

For instance, Assetto Corsa’s tire model has progressed through more than ten different iterations, however, a few issues have come to light in regards to tire wear and blowouts, which seem to cause some issues in regards to the way racing is handled overall in the sim.

In one of my recent live streams, I showcased IndyCar content that was released by VRC Modding Team. I had it set to a 51 lap race around the mod’s version of Texas Motor Speedway, set with authentic fuel and tire wear. I noticed that as I was running the event, my right side tires were going to run of rubber approximately ten laps before the end of the race (as seen at the 1:25:00 mark in my live stream). I had never had a tire blow out on me during a race, so I decided to run out the tires, to see what would happen. However, the tires never went flat, never blew out. I didn’t really even lose too much time due to tire falloff! I was left rather confused, and rather disappointed.

After the Live Stream, I decided to run another experiment. I set up the Dallara DW12 Formula NA 2012 to run around the oval circuit again, and decided to see what would happen if I attempted a full fuel run. I knew the tires were supposed to last approximately 35-40 laps, and the tank in the car would last a little shy of 75 laps. So, it was easy to say that, in theory, the tires should go flat long before the car would actually run out of fuel!

Well, in theory is one thing. In practice is another entirely! While the Assetto Corsa tire app showed that our right side tires “ran out” around lap 40, we were able to go over THIRTY more laps on the “out of grip” tires, with minimal loss in speed. Something was up…

Upon uploading the video evidence to Youtube, there was quite a mixed reception to the news. There seemed to be three main trains of thought regarding the video:

A. Some stated that the evidence was “inaccurate”, accusing the IndyCar mod to be of poor quality.
B. A few comments stated that they were able to “Easily” blow their tires, and this was a “useless experiment”.
C. Some people were genuinely surprised by this discovery.

When I was reading these comments from the community, I noticed an interesting trend, primarily with point “B” on my list. The people who stated that they have encountered tire blowouts stated that they only encountered that when either performing burnouts or drifting. This allowed me to concoct another theory in my head.

For my next experiment, I decided to test out a similar experiment, this time utilizing first-party content, direct from Kunos Simulazioni. For my experiment, I took the Ferrari 488 GT3 race car around the Silverstone GT circuit. This time, I decided to use 3x Tire Wear, so I didn’t have to spend over an hour trying to blow out the tires.

Half a lap into my run, I accidentally spun into Stowe, so I decided to test out the “Burnout” theory. Around 5 seconds later, my left rear tire blew out! So, that at least confirmed the fact regarding blowing tires via burnouts/drifting. However, I was still curious about if you could blow a tire “running down the grip meter”.

I took the Ferrari out for another run, and ran the tires out until the grip meter showed 0%. The tires on the Ferrari were set to last approximately 14 laps (which would be approximately 42 laps, after accounting for tire wear rate). After the tire grip went to 0%, nothing happened. I could feel that the lap time fall-off was more drastic, but that was likely due in part to Silverstone being a flat road course, as opposed to a banked oval. For good measure, I ran an extra lap and a half after the tire wear went down to 0%, and still saw no effects on the tires.

After that experiment ended, I decided to take the Dallara DW12 to Silverstone, and try seeing if I could blow the tires by performing a Burnout. It took less than ten seconds to blow out the right rear tire, so it can be said that this tire issue is not isolated to first or third party content, but was an inherent issue with the tire model itself.

Now some people may be wondering, “What the heck is the point of this experiment?!”. The main point is to expose something that is wrong with the tire model simulation. Part of the responsibility of the Sim Racing community is to bring issues to light, so they can be remedied and resolved in future releases, be it in a patch, or in a future title.

In this case, we are going to be having Assetto Corsa Competizione coming later this year. Unlike Assetto Corsa, which was initially designed for shorter, sprint style events (before support was added for pit stops and longer events), Competizione is being designed with endurance events in mind, such as the 24 Hours of Spa. Having a flaw like this in the sim could open up flaws in the competition model, and racing behavior that could be perceived as unrealistic.

Hopefully, with the physics and tire models being improved in the upcoming release, we will see a more dynamic tire model, that will allow for more improved tire wear, and blowouts due to extended abuse of tires. Time will tell, but hopefully we’ll be able to find out soon enough, when we get our hands on the AC:C Early Access!

So what are your thoughts on the Assetto Corsa tire model? What improvements would you like to see in Assetto Corsa Competizione? Let us know in the comments!

Editor’s Note: In the future, I’m planning on analyzing other sim’s tire models, seeing what they do well, and what they may struggle with.

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