iRacing Multi-Class Racing Guide

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Multi-class racing—IMSA and endurance series—puts different car classes on track together. LMPs, GTPs, and prototypes share the circuit with GT3s and GT4s. Managing traffic and understanding blue flags is essential for both faster and slower classes.

Blue Flags: What They Mean

Unlike F1, iRacing's blue flag (with yellow diagonal stripe) is informational only. It warns you that a faster car—one or more laps ahead of you—is behind you. The flag appears on screen and your crew chief will announce it, typically when the faster car is within about 2 seconds. It is not a directive to yield; it is a heads-up so you can be aware and predictable.

Blue Flag Etiquette in iRacing

Blue flags are not mandatory. You do not have to pull off-line or brake hard. However, being predictable and cooperative helps everyone. Hold your racing line and allow the faster car to pass safely when it is reasonable to do so. Blocking is still protestable.

When You Are Being Lapped (Slower Car)

Watch the Relative (F3) – Stay aware of closing speed and which side the faster car prefers
Be predictable – Smooth inputs. No sudden lane changes or last-moment moves
Lift on straights – Easing off throttle is often enough. No need to brake hard
In corners – Stay on your normal line. Faster cars will brake earlier; let them choose where to pass
Communicate – Use voice or text ("Pass right", "Lifting") if your league supports it

What Not to Do

Do not fight the lapping car
Do not brake suddenly in the middle of a straight
Do not make unpredictable lane changes
Do not block. Blocking can result in SR penalties and protests

When You Are Lapping (Faster Car)

Be patient – Wait for a safe place to pass. Do not force it in a risky corner
Use flashes sparingly – A quick flash can signal intent, but repeated flashing is poor etiquette
Anticipate their line – Slower cars may not see you until the last moment. Plan your move early
Pass on straights when possible – Cleaner and safer than diving into corners

Tip: In multi-class, the faster class has responsibility to pass safely. The slower class must be predictable. Both sides need to cooperate.

Traffic Strategy

In endurance races, traffic management can decide the result. Lose time by getting stuck behind GTs, or gain time by passing cleanly. Study track maps for passing zones—long straights, wide corners—and plan where you will make your moves. Avoid passing in the middle of a complex section where the slower car cannot easily yield.

Next: explore our Driver Guides hub for the Endurance Guide (coming in Phase 3), or our Braking Techniques Guide for performance.