iRacing 2026 Season 4 Adds Four Cars, Three Rebuilt Tracks, and a Physics Overhaul

iRacing's 2026 Season 4 build arrives ahead of an official season start on September 15th at 0000 UTC, bringing one of the service's four annual content drops with it.

What changed

New cars:

• Aston Martin Valkyrie AMR-LMH
• Caterham Academy
• Caterham 420R
• Gen 4 Grand National

Rebuilt tracks (fully replacing older versions):

• Road America
• Mid-Ohio Sports Car Course
• The Milwaukee Mile

Major artwork updates to Summit Point Raceway and Road Atlanta.

Physics and mechanics:

• The physics processing engine has been upgraded to support multi-threading, described as making object interactions more accurate
• Significant vehicle mechanics overhauls for the Global Mazda MX-5 Cup and the Sprint Car, with both said to drive closer to their real-life counterparts

Features and systems:

• Car Rule Sets are now available on dozens more vehicles
• Full UTF-8 character support has been added across the simulation — covering chat, display names, replays, setups, and camera set filenames
• A new Reference Car UI element has been introduced (source text truncates before full detail)
• Dedicated pace cars per class, intended to replicate real-world multiclass race starts, are pending a shakedown in the Week 13 iTested series before joining the IMSA iRacing Series

For regular iRacing subscribers, the multi-threading physics upgrade and the twin MX-5/Sprint Car overhauls are the changes most likely to be felt immediately behind the wheel.