2018 Audi S4 Wheel Interchange

2018 Audi S4 Wheel Interchange and Fitment Guide

When you swap wheels on a 2018 Audi S4, the main problem is balancing brake clearance, fender clearance, and correct hardware under real-world constraints. The on-page calculator lets you compare a donor setup against your S4, but you still need safe assumptions and validation. Below is the process I use in the shop to plan, check, and confirm a fit without guesswork.

1. Goal

Define a wheel and tire setup for a 2018 Audi S4 that fits safely, matches critical mounting specs, and passes physical validation on the car using the calculator and basic checks.

2. Prerequisites

• Known OEM baseline for the 2018 Audi S4 (may vary by trim/package):

• Other OEM sizes may exist by trim/package. If your sticker or build sheet shows different sizes, use those as your baseline. You can confirm with the calculator on this page and OEM sources.
• Basic tools: torque wrench, appropriate socket, jack and stands, and a way to measure clearances.
• Optional tools and parts: 1/2 inch torque wrench, M14x1.5 lug bolts, 66.5 hub-centric rings, tread depth gauge.

Seat type for lug bolts can vary by wheel design. Verify with the wheel manufacturer. Do not mix seat types.

3. Step by step

3.1 Establish your baseline

Use the OEM setup above as the “Installed on (your vehicle)” baseline in the calculator. If your door-jamb sticker or build sheet lists a different OEM size, enter that instead.

3.2 Enter the donor wheel or custom size

• If you know the donor vehicle’s wheel specs, select it in “Wheels from (donor vehicle).” Then confirm the exact rim width, diameter, and offset if available.
• If you are planning an aftermarket setup, use “Custom wheel size.” Enter rim diameter, width, and offset. Then enter the “Custom tire size.” Adjust section width and aspect ratio as needed. The calculator updates tire diameter as you change rim diameter.

3.3 Check critical mounting constraints first

• Bolt pattern: your S4 is 5x112. A different PCD is not recommended.
• Center bore: hub is 66.5 mm. Wheels with a larger bore need 66.5 rings. Smaller bore will not fit the hub.
• Thread size: M14x1.5. Match your bolts and seat profile to the wheel design.

3.4 Evaluate clearance changes with the calculator

• Inner clearance: watch the inboard move toward the strut and control arms. More positive offset or wider wheels reduce inner clearance.
• Outer “poke”: watch fender and liner clearance. Lower offset or wider wheels push outward.
• Tire diameter: keep overall diameter close to stock to protect speedometer and driving aids. A small variance is common; use the calculator’s percentage change as your guide.

3.5 Consider practical trade-offs

• Wider tires can improve grip but may rub at full lock or over bumps.
• Lower offset can enhance stance but increases fender risk and steering kickback.
• Larger diameter reduces sidewall and ride comfort. Brake clearance can improve, but bending risk rises with thin sidewalls.

3.6 Plan hardware and accessories

• Hub-centric rings are recommended when wheel bore exceeds 66.5 mm.
• Verify bolt length when using spacers or different wheel pad thickness. The engaged thread length should meet manufacturer guidance.
• TPMS: reuse sensors if compatible, or source compatible units for your wheels.

4. Validation

• Physical test-fit: mount one front and one rear. Spin each by hand and check for contact.
• Brake caliper clearance: confirm at least visible daylight around caliper faces and barrel. Inspect spoke-to-caliper clearance at multiple clock positions.
• Fender and liner clearance: turn lock-to-lock, compress suspension with a jack under the control arm, and recheck.
• Road test: drive at multiple speeds. Feel for vibration, rubbing, or steering pull.
• Torque: tighten lug bolts to the value specified in the Audi owner’s manual, then re-check torque after 50–100 miles.
• Speedometer check: compare GPS speed to the cluster. The calculator’s tire diameter change should match what you observe.

5. Troubleshooting

• Vibration at highway speed:
  • Validation: confirm hub-centric fit. If the wheel bore is larger than 66.5 mm, install proper rings.
  • Action: road-force balance the tires and recheck torque in a star pattern.
• Rubbing on turns or bumps:
  • Validation: review calculator inner/outer shifts versus OEM.
  • Action: consider a slightly higher offset, narrower tire, or adjust camber within spec. Ensure liner clips are intact.
• Bolts bottoming or too few threads engaged:
  • Validation: measure bolt shank versus hub depth and wheel pad.
  • Action: use correct-length M14x1.5 bolts with the proper seat profile for your wheel.
• TPMS warning:
  • Validation: check sensor IDs and battery status.
  • Action: relearn procedure per Audi guidance or install compatible sensors.
• Steering feel changes:
  • Validation: compare scrub radius and track change in the calculator.
  • Action: select an offset closer to OEM, or reduce spacer thickness.

6. Wrap up

Start with the 2018 Audi S4 OEM baseline above, then use the calculator to model any donor or custom setup. Keep the bolt pattern, center bore, and thread size identical. Use offset and tire size changes thoughtfully, with clear validation for brake and fender clearance. When values are unknown or vary by trim, verify them on your vehicle label and with OEM documentation before buying. With careful planning and a methodical check, you can move from uncertainty to a confident, clean fit.