2009 Audi S8 Wheel Interchange

tl;dr

• OEM baseline for 2009 Audi S8: 20x9 ET45 with 265/35R20.
• Bolt pattern 5x112. Center bore 57.1 mm. Thread M14 x 1.5.
• Backspacing is 6.27 in. Use hub centering on 57.1 mm.
• Use the on-page calculator to compare changes before you buy.
• Confirm torque value and lug seat type in OEM sources.

Recommendation

Start from the factory spec and make small, measured changes. Use the wheelinterchange.com calculator to compare any donor wheel or custom size against your S8. Keep overall tire diameter close to the OEM tire to protect speedometer accuracy and driver aids. Maintain hub centering on 57.1 mm. Verify brake and fender clearance before mounting tires. If anything is unknown, confirm it with the calculator and your OEM documentation.

Impact

Offset and track width

Offset changes move the wheel in or out. More positive ET tucks the wheel inboard. Less positive ET pushes it outward. Inboard moves risk suspension and liner contact under compression. Outboard moves risk fender or arch contact on bumps and turns. The calculator shows these shifts in millimeters so you can visualize the change.

Width and clearance

Wider rims add tire section width and bulge depending on tire choice. Inner clearance to struts and control arms is the usual limit. Outer clearance to the fender lip is the next constraint. The calculator compares inner and outer positions versus OEM, which helps you gauge safe room.

Tire diameter and ride

Tire outside diameter affects speedometer, gearing feel, and ABS stability tuning. The calculator updates tire diameter when you change rim diameter, so you can keep total diameter close to stock. That preserves handling balance and avoids false ABS or stability events.

Hub, bolts, and vibration

Your hub bore is 57.1 mm. Aftermarket wheels with larger bores need 57.1 rings to stay hubcentric. Smaller bores do not fit. Thread size is M14 x 1.5. Lug seat type can vary by wheel, so match the seat to the wheel design. Mismatched seats can loosen and cause vibration.

Risks

• Brake caliper spoke contact from low offset or wrong spoke profile.
• Inner liner or knuckle rub under load with wider setups.
• Outer fender contact on compression or full lock turns.
• Vibration from running lugcentric without proper 57.1 rings.
• Lug seat mismatch causing bolt loosening or damaged seats.
• Incorrect bolt length bottoming in hubs or not engaging enough threads.
• Speedometer error and stability control quirks from big tire diameter changes.
• TPMS compatibility can vary by market and equipment. Confirm on your car.

Next actions

Checklist

• Confirm the baseline below matches your trim and build.
• Open the on-page calculator. Set Installed on to 2009 Audi S8.
• Compare a donor wheel or enter Custom wheel size and Custom tire size.
• Review inner clearance, outer poke, and tire diameter differences.
• Check brake spoke clearance using a straight edge and ruler after a test fit.
• Verify hub bore 57.1 mm. Plan hubcentric rings if the wheel bore is larger.
• Match lug seat type to the wheel. Confirm M14 x 1.5 thread.
• Torque to OEM spec in a star pattern. Recheck after 50–100 miles.

How to confirm unknowns

• Torque spec and lug seat type: owner’s manual or OEM service info.
• Brake clearance: use the calculator, then test fit with no tire, rotate, and inspect.
• Fender clearance: load the suspension and steer to full lock both directions.
• TPMS type: check your cluster, valve stems, or parts catalog for your VIN.

Known OEM fitment for 2009 Audi S8

Gotchas

• Do not force smaller hub bores onto a 57.1 hub. They will not fit.
• Do not rely on lug bolts to center the wheel. Use proper rings if needed.
• Do not guess bolt length or seat type. Verify against your wheel design.
• Spacers and extended hardware require precise measurements and quality parts. Measure first.

Helpful tools

• 1/2 inch drive torque wrench
• Wheel hanger guide pin M14 x 1.5
• Hubcentric rings 57.1 mm
• Digital caliper for measuring bores and bolts

If any value differs by trim or region, use the calculator and OEM sources to confirm before purchase. Small, verified changes reduce risk and keep the S8 driving as intended.