iRacing 2026 Season 4 is out. The build is 2026.09.09.01, it was released on 9 September 2026, and the season started on 15 September. This is what changed, and what I would do with it.
My sources are the iRacing release article and racinggames.gg from 10 September, plus search summaries of the official notes on support.iracing.com. The notes page did not load for me today, so for the long tail of small fixes read it yourself. I have not driven the build, and where I say what I would do, that is a plan and not a test.
New cars
| Car | What it is |
|---|---|
| Aston Martin Valkyrie AMR-LMH | A modern Le Mans Hypercar prototype, rain ready at launch |
| Caterham 420R | A Caterham Seven, sold as a package with the Academy |
| Caterham Academy | The Academy version of the Seven, rain ready at launch |
| Gen 4 Grand National | A return to the early 2000s stock car |
The article does not list classes. All four new cars are AI enabled at launch, according to racinggames.gg.
The one most people will care about is the Valkyrie. If you drive in the IMSA series or the other GTP races, check my IMSA series guide and the best GTP cars to buy page before spending the money.
Photo of the real car: BouncyCactus, Wikimedia Commons, CC BY-SA 4.0.
Photo of the real car: Calreyn88, Wikimedia Commons, CC BY-SA 4.0.
Tracks
| Track | Change |
|---|---|
| Road America | Rescanned and rebuilt. Four configurations, with two new Short layouts |
| Mid-Ohio Sports Car Course | All five layouts rescanned and rebuilt |
| Milwaukee Mile | Rescanned and rebuilt, with the infield road course as a second layout |
| Summit Point Raceway | Appearance update |
| Michelin Raceway Road Atlanta | Appearance update |
One thing to know. A track rebuilt from a new scan replaces the old one. The bumps, the camber and the kerbs move, so a lap time or a setup from last season at Road America is not a safe reference. Re-learn the braking points on the first session.
Road America. Photo: Michael Barera, Wikimedia Commons, CC BY-SA 4.0.
Mid-Ohio. Photo: redlegsfan21, Wikimedia Commons, CC BY-SA 2.0.
Physics
Two changes are about the cars themselves:
- The Global Mazda MX-5 Cup and the paved Sprint Car got major physics and art updates. iRacing says they should drive closer to their real counterparts.
- The physics engine is multi-threaded, which iRacing calls Physics Islands. The company says it can cut CPU physics overhead by 50% or more in large grids and heavy traffic. It also lays the ground for faster physics tick rates and higher force feedback update rates later. That is a plan, not a feature you can switch on today.
If you race the MX-5 or the Sprint Car, your old setup is a starting point, not an answer. My Sprint Cars list has the cars. Do your usual quick test: five laps on a track you know, change one thing.
Interface
- Pit Summary widget for all vehicles, and a Car Damage widget for selected vehicles.
- A Reference Car UI in Time Trial, Time Attack and Test Drive.
- A Minimal or Pinned UI mode.
- Track map updates and an improved Fuel Calculator widget.
Multiclass starts
iRacing plans class specific pace cars so multiclass starts look more like the real ones. The reports I found say the feature has to pass a shakedown in Week 13 of the iTested series before it joins the IMSA series, and they disagree on how wide the rollout is in Season 4. I would not plan a race around it. Check the official notes for the scope.
What I would do first
- Read the official notes once, top to bottom. Five minutes.
- Run a practice session at Road America or Mid-Ohio in a car you know, to learn the new scan.
- If you race the MX-5 or the Sprint Car, redo your setup from the baseline.
- Wait a week before buying the Valkyrie. The first patches often change the balance of new cars.
FAQ
When did iRacing 2026 Season 4 start?
The build, 2026.09.09.01, was released on 9 September 2026. The competitive season started on 15 September.
What new cars are in iRacing 2026 Season 4?
The Aston Martin Valkyrie AMR-LMH, the Caterham 420R, the Caterham Academy and the Gen 4 Grand National.
Which tracks changed in iRacing 2026 Season 4?
Road America, Mid-Ohio and the Milwaukee Mile were rebuilt from new scans. Summit Point and Road Atlanta got appearance updates.
Did the physics change in Season 4?
Yes, for the Global Mazda MX-5 Cup and the paved Sprint Car. The physics engine also moved to multi-threading.
Is the new Valkyrie rain ready?
Yes. The Valkyrie and both Caterhams are listed as rain enabled at launch.
Do my old setups still work?
For rebuilt tracks and the two cars with new physics, treat them as a starting point only.