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2018 Porsche 911 GT3 Wheels & Rims: Bolt Pattern, Offset & Sizes
Fitting Porsche 911 GT3 wheels? This page gives the 2018 Porsche 911 GT3 bolt pattern, centre bore, factory rim size and the offset range for aftermarket and forged Porsche 911 GT3 rims: the same spec sheet ANKUSI uses when machining forged wheels for this car.
Porsche 911 GT3 (2018): Porsche centerlock hub, 71.6mm center bore. Factory wheels: F: 20x9J R: 20x12J. Reference fitment ranges.
Bolt PatternCenterlock
Wheel Bolt/NutCentre-lock single nut (600 Nm, 3/4in drive)
Center Bore71.6mm
Wheel Load Rating700–850 kg/wheel (Performance / Sports Car segment reference)
Caliper TypeFixed 6-piston front caliper (OEM, Porsche GT/RS)
Year2018
CategoryTrack Sports Car
Data check: the bolt pattern and center bore on this page have not yet been confirmed by a second independent source. Measure your hub or ask us before ordering. How we verify
Wheel Size & Offset at a Glance
| Configuration | Wheel Size & Offset |
|---|---|
| Flush Fitment | F 20x9J ET45 / R 20x12J ET45 |
| Maximum Aggressive | F 20x9J ET45 / R 20x12J ET45 |
Forged Wheel Designs for the Porsche 911 GT3
Every design below is forged to order, so it can be machined to the Porsche 911 GT3's bolt pattern and 71.6 mm center bore, with the width and offset calculated for your setup.
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How to Read Wheel Offset & Measurements
Use these two references before ordering: the left diagram shows where each spec (PCD, center bore, offset, width and diameter) is measured on the wheel; the right diagram shows how positive, zero and negative offset shift the wheel face relative to the hub centerline.
ANKUSI Engineering Expert Advice
On a track-focused car the factory already spent the unsprung-weight budget carefully, so the aftermarket brief is narrow: same footprint, less mass, more barrel clearance for the brake package. Chasing poke on a car like this usually costs lap time before it buys looks.
The Porsche 911 GT3 runs a Centerlock fitment, 71.6mm center bore, and a F: 20x9J wheel from the factory. Our Flush Fitment reference is F 20x9J ET45 / R 20x12J ET45 - on this car the published aftermarket guidance is that the factory footprint already sits flush. Our Maximum Aggressive reference is F 20x9J ET45 / R 20x12J ET45 - the verified data does not support going wider than the flush spec on this chassis.
Porsche 911 GT3 OE Wheel Specs
The 2018 Porsche 911 GT3 (Track Sports Car) runs a Centerlock hub with a 71.6mm register. Factory wheels are F: 20x9J R: 20x12J.
Why the factory spec works for most owners:
- Keeps unsprung weight low to preserve the factory handling balance
- Matches the wider, performance-oriented tire sizing typical of this platform
- Maintains clearance for the factory brake package and suspension geometry
- Balances grip with ride comfort for daily and spirited driving
ANKUSI builds these wheels — we are the forging factory, not a reseller. For the Porsche 911 GT3 (2018) we cut the centre bore to 71.6mm on our own CNC line, so the wheel hub-centres on the car with no spacer rings, in whatever diameter, width and offset you specify.
Converting these ET figures to backspacing? Use the wheel offset and backspacing calculator.
The figures on this page are part of our open wheel fitment dataset — 10,093 vehicles, free to download, CC BY 4.0.
Real-World Fitment Notes
the aftermarket route is buying centerlock forged wheels directly (Forgeline GT1/GE1/GA1R centerlock, APEX VS-5RS/EC-7RS centerlock, HRE) — NOT a bolt-on adapter conversion centerlock torque spec is critical; brand wheels ship with a matched centerlock nut/spline (data from same 991.2 GT centerlock platform)
Offset & Backspacing Reference
Backspacing is calculated as wheel width (in) ÷ 2 + offset (mm) ÷ 25.4 + 0.5 (flange allowance):
- OE: F 20x9J ET45 → ~6.77″ F backspacing, R 20x12J ET45 → ~8.27″ R backspacing
- Flush: F 20x9J ET45 → ~6.77″ F backspacing, R 20x12J ET45 → ~8.27″ R backspacing
- Max: F 20x9J ET45 → ~6.77″ F backspacing, R 20x12J ET45 → ~8.27″ R backspacing
A Note on Clearance
Final clearance depends on the exact tire model, suspension height, brake package, alignment and vehicle tolerances. A physical test fit is recommended before production.
Want to check a different width or offset before you order? Use our Offset & Backspacing Calculator to solve the numbers yourself, or looking for your exact Porsche spec, or want a wheel built to a custom offset for your Porsche 911 GT3? Contact ANKUSI with your bolt pattern and offset target and we will confirm the correct forged wheel spec for your build.
Frequently Asked Questions
What is the center bore size on the Porsche 911 GT3?
The Porsche 911 GT3's center bore is 71.6mm. If an aftermarket wheel has a larger center bore than this, hub-centric rings are recommended so the wheel centers on the hub itself rather than relying on the lug bolts alone.
What is the biggest wheel size I can fit on my Porsche 911 GT3 without rubbing?
The most aggressive fitment we recommend without fender work is F 20x9J ET45 / R 20x12J ET45. Going beyond this typically causes rubbing under compression unless you roll the fenders or add camber correction.
What does a flush wheel fitment look like on the Porsche 911 GT3?
For a flush look with minimal to no rubbing, we recommend F 20x9J ET45 / R 20x12J ET45 as a starting point on a stock or mildly lowered Porsche 911 GT3.
Do I need wheel spacers for my Porsche 911 GT3?
No. ANKUSI forges each wheel to your exact target offset, including the flush or max specs above, so you get the correct fitment without stacking spacers. Spacers are typically only used to push out an existing OE-offset wheel without replacing it, which isn't necessary when you're ordering a custom-offset forged wheel.
How do I calculate wheel backspacing for my Porsche 911 GT3?
Backspacing (in inches) = wheel width (in) ÷ 2 + offset (mm) ÷ 25.4 + 0.5 (flange allowance). For example, the flush spec above works out to roughly 6.77" backspacing up front and 8.27" in the rear.
What's the difference between wheel offset and backspacing?
Offset is the distance in millimeters from the wheel's true centerline to its mounting face (positive offset pulls the wheel in, negative pushes it out). Backspacing is the distance in inches from the mounting face to the back edge of the wheel barrel. They describe the same fitment from two different reference points, which is why ANKUSI lists both above — some shops and tuning guides quote offset, others quote backspacing.
Can I run staggered wheels (different sizes front and rear) on my Porsche 911 GT3?
Yes — the Porsche 911 GT3's factory and our recommended flush/max fitments already use staggered sizing (different width front and rear), and ANKUSI can forge matching staggered sets to your target offsets.