What Class Is a Porsche GT3 in NASA TT?

Short answer: a stock 992 GT3 on its factory tires is a TT1 car, with enough ratio headroom that mild modifications don't move it. But the answer changes by variant, and one rule — active aero — flips the whole question for the RS. Here's the family, classed.

The quick table (stock configuration, typical driver weight)

Car	Typical adjusted ratio	Class	The catch
992 GT3 (PDK, Cup 2)	~9.6	TT1 (TT2-legal on numbers)	Cup 2's +2.0 factor does heavy lifting
992 GT3 (manual)	~9.8	TT1/TT2 borderline	No PDK deduction
992 GT3 RS (DRS active)	n/a	TTGT or TTU only	Active aero illegal in TT1–TT6
992 GT3 RS (DRS disabled)	~7.5	TT1	Full worked example
718 GT4 / Spyder	~11.5–12	TT2/TT3 territory	Tire choice decides which
718 GT4 RS	~9.5–10	TT2	High-revving NA averaging works in its favor
GT3 Cup (991/992)	listed race car	TT1/TT2 with listed factors	Factory race cars get Production status per ST 6.5.4

Numbers assume stock power on the factory-fitment tire with a ~180 lb driver; your dyno sheet and scale weight govern. The point of the table is the pattern, not gospel — verify your build in the TT Engineer tool.

The three rules that decide Porsche classing

Active aero (ST 6.1.1). RS models with functioning DRS are excluded from every numbered class. Disable and fix the system to class normally, or run TTGT with everything live and skip the paperwork entirely.

Tire factor dominates. A GT3 on Cup 2s (+2.0) versus the same car on Cup 2 Rs (+0.0) is a two-point swing — often the entire distance between comfortably-TT1 and TT2-legal. For Porsches, tire selection is class selection; the formula article shows the full factor table.

PDK is worth −0.2 in TT1/TT2, −0.5 in TT3/TT4. Small, but on borderline builds it's the difference-maker, and manual cars get nothing.

Which class should you actually run?

If your GT3 is also your street car: class it honestly, run it on 200TW tires, and you're both TT-legal with margin and eligible for the new TT Street overlay — the best value in the 2026 rulebook. If you're chasing hardware: the class-by-class guide and the first-class decision article cover strategy, and the honest answer for most GT Porsches is that TT2 offers better fields-to-pace ratios than TT1 in many regions. Start-to-finish onboarding lives in the complete guide.

FAQ

Does a GT3 Touring class differently than a GT3? No meaningful difference — same drivetrain and power; the wing delete doesn't generate a factor since production-car aero in TT1–TT3 is free within the universal limits.

Where do Cup cars go? Listed factory race cars carry specific factors under ST 6.5.4 (991 Cup: −0.0 in ST1, −0.2 in ST2) and get Production-car status rather than the sports-racer penalty. Practically: TT1, or TT2 with the listed deduction — run the numbers.