When I raced GT3 machinery in real life, half the job had nothing to do with my own lap time. It was mirrors. Faster prototypes arriving with a 30 km/h closing speed, three corners of warning, and one chance to not ruin both our races. The IMSA iRacing Series recreates that exact problem every 45 minutes, and that's why it's the sports car series on iRacing I point everyone toward once they're out of the beginner ranks.

Here's the full picture: what the series is, the three classes, the current schedule, how the open and fixed versions differ, and the strategy that actually wins these races.

What the IMSA iRacing Series is

It's iRacing's flagship multiclass road series: GTP prototypes, LMP2 and GT3 cars sharing the same track, mirroring the real IMSA SportsCar Championship. You race one class and manage the other two.

The key numbers, as of Season 3 2026:

  • License: Class B 4.0 to enter
  • Race length: 45 minutes (open setup) with sessions going off every 2 hours
  • Season: 12 weeks, 4 drop weeks
  • Incidents: hit 25x in a race and you're disqualified on the spot
  • Grid: 16 cars are eligible across the three classes

That 25x DQ rule matters more than people think. In most series you can have a scrappy race and limp home. Here, wall contact plus a couple of unlucky sandwiches in traffic can end your night with zero points. It rewards exactly what real endurance racing rewards: staying out of trouble.

If you're still working up the license ladder, my guide to raising Safety Rating is the fastest route to B class. And it's worth the climb — week in, week out this series pulls some of the biggest multiclass grids on the service, with multiple splits at most timeslots.

The three classes

GTP — five hybrid prototypes

The headline class: Porsche 963 GTP, BMW M Hybrid V8, Cadillac V-Series.R, Acura ARX-06 and Ferrari 499P. The first four are LMDh cars; the Ferrari is the LMH machine from Le Mans, balanced to match. They're the fastest closed-wheel cars in the sim — huge downforce, hybrid deployment, and a cockpit workload that punishes lazy management.

In GTP you are always in traffic. You'll lap the entire GT3 field, often twice. If you've never driven one, I ranked the class in my best iRacing GTP cars post — start there before spending money.

LMP2 — the Dallara P217

One car, one spec class. No hybrid system to manage, less weight, less downforce than GTP. It's the purest race car of the three classes and, honestly, the best classroom in the series: fast enough to catch GT3 traffic constantly, slow enough that GTPs hunt you down. You learn both sides of the mirror in one stint.

GT3 — ten cars, full BoP field

The GT3 class (GTD in real IMSA) runs ten cars: Mercedes-AMG GT3 2020, McLaren 720S GT3 EVO, Ferrari 296 GT3, Aston Martin Vantage GT3 EVO, Acura NSX GT3 EVO 22, BMW M4 GT3 EVO, Lamborghini Huracán GT3 EVO, Chevrolet Corvette Z06 GT3.R, Porsche 911 GT3 R (992) and Ford Mustang GT3. All BoP'd, all running ABS and traction control.

This is where I'd start if you're new to the series — and note that the Season 3 2026 build (June 16) touched the whole GT3 class with aero, mass, power and TC/ABS changes, plus a follow-up TC fix in the July 14 patch. Old setups are baselines now, not gospel. My iRacing GT3 setups hub and the wider setup archive are exactly that: starting points to build from. Not sure which car? Here's my take on the best iRacing GT3 cars.

The Season 3 2026 schedule

Season 3 started June 16 and runs 12 weeks. As I write this we're in week 8 at Fuji:

  1. Watkins Glen International — Boot
  2. Mobility Resort Motegi — Grand Prix
  3. Circuit de Spa-Francorchamps — Grand Prix Pits
  4. Canadian Tire Motorsport Park
  5. Autódromo José Carlos Pace (Interlagos) — Grand Prix
  6. Road America — Full Course
  7. Monza — Grand Prix
  8. Fuji International Speedway
  9. Daytona International Speedway — Road Course
  10. Virginia International Raceway — Full Course
  11. Road Atlanta — Full Course
  12. Circuit des 24 Heures du Mans

That back stretch — Daytona, VIR, Road Atlanta, then a Le Mans finale — is the best run of tracks on any iRacing schedule this season. If you only buy a few weeks, buy those. The Season 4 build lands in September and resets the calendar.

Open vs Fixed

The series runs as a pair, same B 4.0 license for both:

  • IMSA iRacing Series (open): 45-minute races, full garage access. If you enjoy setup work, this is the version — and tech inspection will police whatever you build.
  • IMSA iRacing Series – Fixed: 35-minute races on iRacing's setups, with in-car tweaks essentially limited to brake bias and your cockpit controls. Bigger entry numbers at many timeslots, zero garage homework.

One detail that catches people: the two versions don't always share a layout. This week the open series runs Fuji without the final chicane while Fixed runs the full Grand Prix loop. Check the week's combo before buying a track. I've broken down how the two formats differ across the whole service in my fixed vs open setup series guide — the short version is that fixed racing is a better measure of your driving than most people want to admit.

Strategy: the pit stop decides more than the start

Races start rolling after a short lone qualifying session, and the format is built around a mandatory pit stop. That stop is where midfield finishes turn into podiums.

The tires generally live longer than the fuel window, which opens the classic sports car playbook:

  • Fuel-save from lap one. Every liter you don't burn is time saved at the stop. Short-shifting and lifting 50 meters early costs tenths per lap and wins seconds in the pits.
  • Question every tire change. Fuel-only stops are brutally fast. If you do take rubber, two tires on the loaded side is often the right call — a full set rarely pays back in 45 minutes.
  • Pit into clean air, not just an empty pit lane. In multiclass, rejoining ahead of a GTP train you were about to meet is worth more than a perfect in-lap.

I've written more on the decision-making side in how to make pit decisions in iRacing, and if you're chasing pace before the stop even matters, start with tire pressures.

Traffic is the real skill

Every quick driver in this series can hotlap. The ones who win are the ones who lose nothing in traffic. What I learned doing this for real:

  • Slower class: be boring. Hold your line, stay on the racing line, lift nothing. The GTP behind you has planned his pass around your predictability. The worst thing you can do is "help" by darting offline.
  • Faster class: pass on your terms. Plan the overtake a corner early, use straights, and never arrive at an apex side-by-side with a GT3 who hasn't seen you. If the gap needs their cooperation, it isn't a gap.
  • Use the relative black box constantly. Class colors tell you what's coming long before your mirrors do.

The etiquette is identical to what I wrote in my ACC multiclass racing guide — different sim, same physics of patience.

What it costs

Cars are $12.95, and nearly every track on the IMSA schedule is paid content. Running all 12 weeks from a standing start works out to roughly $200 with one car — but remember the 4 drop weeks: you only need 8 counting scores, so most people buy 8-10 tracks and skip the rest. Full membership math is in my iRacing subscription cost breakdown.

FAQ

What license do I need for the IMSA iRacing Series?

A Class B license at 4.0 Safety Rating or better, for both the open and fixed versions. That's a step down from the A license the series demanded a few years ago, so if you last checked in 2023, it's more accessible now.

How long are IMSA iRacing Series races?

45 minutes in the open-setup series, 35 minutes in the Fixed series, with sessions launching every 2 hours around the clock. Both are built around a pit stop.

Which class should a beginner pick?

GT3. The cars have ABS and TC, the class is the slowest on track, and your only traffic job is staying predictable while being lapped. Move to LMP2 once you're comfortable, and treat GTP as a destination — it's a rolling cockpit-management exam.

Do I have to buy all 12 tracks?

No. With 4 drop weeks, 8 scored weeks count toward the championship. Pick the tracks you already own or actually want, and plan purchases around them.

Is there a team or endurance version?

This series is single-driver sprints. iRacing's separate IMSA Endurance Series and special events like the Daytona 24 cover the long-format side — same classes, longer stints, driver swaps.