iRacing Dynamic Track Guide And Resources

Dynamic Track

Welcome to my iRacing Dynamic Track Guide.  In this guide, I will describe the iRacing Dynamic Track and provide updates and information relating to the track with updates as time goes on.

What Is The iRacing Dynamic Track

The dynamic track within iRacing is iRacing’s way of making the race circuit come “alive” so to speak.  The track simulates, track temp, rubber going down from the cars and marble build up.

iRacing does all of this by simulating the rubber going down from the number of cars on the race circuit.  Just like in the real world.  As the cars go around the circuit they transfer heat and rubber to the surface.  As this builds up the track will rubber in and a dark groove will form.  Once the track has a good amount of rubber down, marbles will start to show.

Another feature that iRacing has implemented in the last 12 months is a day to night transition and a dynamic sky.  As you can imagine cloud cover around various parts of the circuit can affect the temperature of the road below, as can the cooling from going to day to night.

How The iRacing Dynamic Track Is Put Together

Daniel G (iRacing staff) post (10.09.15):

There are a couple of relationships going on that will hopefully help explain why something may not meet one’s first expectations with regards to track rubber and marbles. First, track rubber…


The rate at which the track will accept rubber from the tires is inversely related to the amount of rubber already there.

Say what? Simply put… a clean track will increase in rubber more quickly than a track that already has rubber. The rate at which rubber will be added tapers off and eventually reaches zero when the track is effectively saturated with usable rubber (at least it helps to think of it this way).


The rate at which marbles are created is directly related to the amount of rubber on the track.

Meaning, a clean track is going to produce very, very few marbles, but if there is a lot of track rubber, marbles will be produced at a healthy rate.


Think of your tire as losing rubber as it goes, much more so when it is working hard. On a green track that rubber will help rubber in the track; on a track already pretty full of rubber, most of it will go towards marble production instead. On a track with moderate usage, some go towards rubbering in the track, some goes towards marbles, it all depends!

This is why if you play with usage percentages in testing, you’ll see that going from 0% to 50% mostly puts down track rubber, but 50% to 100% might widen the groove more than it darkens the heavily-used parts, but the marbles (if left on track) really start showing up!

iRacing Dynamic Track Information

What Effect Does The Track State Slider Have?

iracing dynamic track

Daniel G (iRacing staff) post (9.10.15):
The usage slider controls the amount of prior activity, but no heat from those simulated sessions are put into the track. It determines the amount of rubber and marbles. The other factors such as the angle of the sun, how well the track is the surface is facing the sun, clouds, temperature characteristics of the surface, and shadows determine the temperature at a particular spot on the track. But a track with more rubber will be darker, so yes the racing line will be a bit warmer as a result of solar energy.

You could argue for a second slider perhaps, “Time since [end of] prior session” that would potentially leave some heat from prior running.

But to address the topic of the OP (Does track starting state effect lap times and grip?): it should be clear there are many variables involved here. If you put the sun up high in the sky with no clouds on a concrete track, a bunch of rubber is going to probably hurt lap times compared to a clean track. If you put the sun low and make it overcast on dark asphalt, more rubber should improve lap times. Until you are on a short track with 43 cars all running the same line for 40 laps

another Post:
Currently, there is no elevation factor but I could add one, that seems reasonable… and perhaps counter it with an air-quality factor per track as well, if that data is available.  There’s almost no end to the level of detail in which you can model something, just ask DK about tires sometimes.

Visual Graphics Settings To Consider

iracing dynamic track

Dave G (iRacing staff) post (11.09.15):
Soft particles allow for a smoother transition when a particle intersects geometry.
It is probably most notable if you burn out and generate a lot of tire smoke.
Without soft particles, you will see a distinct line where the smoke intersects the track and car.

Dave G post:
The only difference at the moment is High Detail enables soft particles.
Going forward this setting will control more aspects of the particle system.

Dave G post:
The other thing to try is turning Particle quality down to Medium Detail.
At High, it enables “soft particles” which requires a bit more rendering.

Dave G post (17.09.15):
Why marbles in front of the car look ok, otherwise not:
This is your “Anisotropic Filtering” graphics setting. The marbles are particularly sensitive to it. Setting that value higher will give better-looking marbles in the distance at the cost of some performance (depending on your hardware). Particle settings don’t change the on track marble visuals.


iRacing Dynamic Track In The Release Notes

From 2019 Season 4 release notes

– A new track temperature model has been added to the Simulation!
– – This upgraded model now utilizes multiple layers beneath the ground to track temperature and moisture, as well as simulating three days of weather prior to an event start time for generating the track initialization. This track model also continues to run and generate data that will be used for additional sessions if there is a skip between sessions. The multi-layer approach means that the temperature on the surface will behave more realistically. Also included is a more accurate interaction between water and temperature, which can result in the track being cooler than the ambient air temperature if the conditions are right.
– – The end result compared to the previous Dynamic Track model should be that temperatures will likely be cooler in the morning and early afternoon, and warmer in the late afternoon. With the previous system, as the sun sets, the track temperature cools rapidly with the incoming solar energy gone. With this new model, the heat that is built up (especially if the skies have been clear) in the layers of earth below will work its way back up and warm the surface. Similarly, built-up heat from cars will last longer if a lot of laps have been driven. The layers allow a realistic recording of history that the old model simply could not.
– – Think especially about a very short, mild rain shower — in the old model, the track temperature would plummet and never come back up, even after all the water was gone. With the new model, heat is retained in the lower layers and the surface may regain some of the lost temperatures.
– – Also significant, when a session starts, the track temperatures are no longer calculated using the cloud conditions at the session start time. This meant if a session happened to start with the sun obscured, the track would have been unrealistically cool. In the new model, if the sun is out most of the time leading up to that moment, that will be captured and the track will still be hot but cooling off.

– The effectiveness of using a dirt cushion has been reduced.

From 2019 Season 3 release notes

– The total amount of solar energy allowed to penetrate through clouds and adjust the track surface temperature has been increased. This will cause clouds to have a reduced effect on temperature changes.

– The Track Conditions information on the Info tab of the Session screen has been updated to include all Sessions, and now uses the same Session names as the Race Details area.

From 2019 Season 2 release notes

– The system for calculating track temperature as reported to the user in the Info tab and telemetry has been improved.

From 2018 Season 3 release notes

– The reported track temperature will now be dynamically updated throughout a session.

From 2018 Season 2 release notes

– Some updates have been made to the debris throwing system.
– – The physics for debris now utilizes a new collision system. This should eliminate the ability of thrown particles to slip through walls, making their build-up more accurate.

From 2018 Season 1 release notes

– Improved the method for calculating simulated tire activity during track initialization.

From 2017 Season 4 release notes

– The visuals for marbles have been improved.

– Fixed an issue whereby a Lone Qualifying session would trigger an error that made some parts of the track on a client unable to send all updates to the server in any sessions which followed, such as an attached race.

From 2017 Season 3 release notes

– Fixed a bug that allowed an exploit of joining an event during a lone qualifying session and not inheriting the track state from a prior session. This was especially noticeable in a dirt hosted session with a long practice session before qualifying.

– The rate of conduction and convection of heat from the track has been decreased, which will result in higher track temperatures and quicker buildup of heat due to the running of cars on track.

From 2017 Season 1 release notes

– The marbles texture has been updated to provide more accurate information on marble density.

– Fixed an issue that could allow the server to create track dust when processing client updates.

From 2016 Season 4 release notes

  • Some extensive updates to the Dynamic Track System have also been added that should increase the realism of heat
    mapping and make rubber have a bit more of an impact on your race.
  • Your experience at night tracks has been improved with the new Dynamic Night Shadow Maps system,
    and every vehicle windshield has been improved with realistic reflections.
  • A new character model has taken the driver’s seat and is also positioned in the pits,
    and you should start to see wind-animated flags appearing at race courses.
  • Increased the effective starting usage level, which controls the amount of rubber on the track, for sessions that have a short Practice and an attached Qualifying prior to a Race.
  • Improved the calculations used to conduct heat from the tire into the track, and updated the conduction and convection model for the track surface. This results in lower starting track temperatures, but a significantly more dynamic range when cars interact with the track.
  • The tearing of rubber from the tires versus from the track has been adjusted so that when a tire is not sliding, it is more inclined to pick up track rubber. Also, the calculations for determining the thickness of the track rubber under the contact patch and the rate at which the track will accept rubber have each been improved. The combination of these changes will make the track rubber build-up about three times as fast, and in general, be more dynamic.
  • The Dynamic Track system now assumes there is some residual starting dust on the track even before any simulated running of cars or cleaning for a session is performed. The amount of starting dust is related to how must dirt and gravel are around that track, such that a track like Mazda Raceway Laguna Seca is more prone to being dusty than a track like Talladega Superspeedway.
  • Dust will now be picked up and thrown due to air displacement near moving vehicles.

From 2016 s3 patch 1 release notes
– For sessions using an Automatically Generated track state, the default starting usage will now vary by a percentage based on the following:
– – Session Type = Such that earlier sessions, such as Practice, are cleaner than later sessions, such as Qualifying. This behavior was originally done and this behavior continues with this update.
– – Time of Day = Such that sessions earlier in the day are cleaner than session later in the day, reflecting usual track usage throughout a given day.
– – Weather = Such that the cloud cover affects the likelihood that relatively recent rain may have compromised track time and/or washed away some percentage of the previous track state. Also, for sessions with Realistic Weather, a random factor is also used to account for variation in track usage due to miscellaneous events prior to the session.

From 2016 s3 release notes
We have performed an extensive update to all track surfaces to better model physics collisions, even with tiny particles like sparks, gravel, and marbles.
The dynamic track surface now includes dust and gravel, which is brought onto the racing surface from off-track excursions and affects tire grip.

– Dust and gravel can now be dragged and thrown onto the track by wayward cars, which then interacts with the tires to affect grip and accumulation of debris on the tires.

– The way the iRacing Dynamic Track is stored in a replay has been improved to allow sudden changes in the track surface state to be seen immediately.

2016 Season 1

Source: iRacing release notes.
  • Marbles on the track are now immediately influenced by both the player car and opponent cars to better simulate the effect of following a car closely through debris.
  • Debris will collect on tires of the player car and then be flung off when appropriate. This means tires will continue to emit grass, gravel, dirt, and marbles even after leaving the associated surface.
  • The in-Sim Info tab now displays actual average race-line temperature at the start of the session as the track temperature, to simulate a crew member taking some sample measurements with a temperature gun pointed at the track a few minutes before the session begins.
  • Improved the way the server broadcasts the track state by allowing it to adjust what it sends depending upon the current situation on a per-client basis.
  • Improved performance when the dynamic track is not being rendered by removing some unnecessary code.

Renderer.ini tweak post by Dave G (18 Dec 2015):
iracing Dyamic Track surface decals are the static visuals that sit on top of the track surface itself.
These are things like the graffiti on Nurburgring, or most start/finish lines, static skid marks or discoloration on the track. The dynamic skid marks are controlled by another system.

MaxTrackDecalsInCockpit – This controls the maximum number of primitives (triangles) that will be rendered for decals while driving. A single decal is typically made up of a fair number of triangles so changing this number by small amounts is not really going to show very different results. Lower values mean more culling and better the framerate, but the fewer decals you will see.

MaxTrackDecalsInMirrors – This is similar to the cockpit value and is the number of primitives for decals drawn in mirrors. One thing to keep in mind is that decals only show up in mirrors with the “Higher Detail Mirrors” setting, so if that isn’t set this value will have no effect.



Be the first to comment

Leave a comment

Your email address will not be published.