2008 Audi S4 Wheel Fitment Guide

Think of this as a clear, safety-first quick recap for picking wheels and tires that actually fit your 2008 Audi S4. I’m using the known OEM specs below and the on-page calculator at wheelinterchange.com to keep things grounded and easy to verify.

1. Misconception

Any 5x112 Audi wheel will fit a 2008 S4 without issues.

2. Why it seems true

A lot of Audi models share the 5x112 bolt pattern. Listings and forum posts often say “it bolts right on.” Photos look fine from the outside. It’s easy to assume the rest will sort itself out.

3. What is true

Fitment is more than bolt pattern. You need the correct center bore, offset, width, and tire diameter. You also want proper thread engagement on the lug bolts and hub-centric support. Spoke design and brake clearance matter too, and those are not guaranteed by the numbers alone.

If your S4 came with a different factory wheel or tire option, that’s fine. Trims and packages can vary. Use your owner’s manual or the driver-door label to confirm your original size, set that as the baseline in the calculator, and compare from there.

4. Implications

Here’s the working mental model. Offset and width shift where the wheel sits in the arch. Lower ET pushes the wheel outward. Higher ET pulls it inward. A wider wheel adds equally to both sides around the mounting face. That affects fender poke and inner clearance to struts, liners, and control arms.

Center bore needs attention. Your hub is 66.6 mm. A donor wheel with a larger center bore can fit, but you’ll want hub-centric rings to keep things vibration-free. A smaller center bore won’t seat without machining.

Lug bolts must match the thread size and seat style of the wheel. Your car uses M14x1.5 threads. The seat type depends on the wheel design, so match the wheel’s seat profile. If you change to thicker wheel pads or add spacers, you may need longer bolts to maintain safe thread engagement.

Tire diameter changes influence speedometer, ABS behavior, and clearance. As a rule of thumb, keep overall diameter changes modest. The calculator shows the impact instantly, which helps you steer clear of rubbing and calibration issues.

Brake caliper clearance is partly about spoke shape. Two wheels with the same numbers can behave differently. That’s why a physical test fit, or a known template, is worth doing before mounting tires.

5. Quick tests

• Calculator sanity check: Set “Installed on” to 2008 S4 with the OEM baseline above. Compare any donor wheel, or plug in a custom wheel width and offset. Watch inner clearance, outer poke, and tire diameter changes before you buy.
• Centering check: If a donor wheel’s center bore is larger than 66.6 mm, plan on hub-centric rings sized 66.6 mm to the wheel bore. This keeps highway vibrations in check.
• Lug engagement: After a hand install, confirm solid thread engagement for each M14x1.5 bolt. If you used spacers or thick wheel pads, verify bolt length is still adequate.
• Lock-to-lock clearance: With the car on the ground, turn the steering from lock to lock. Listen and look for liner contact, especially with wider wheels or wider tires.
• Compression check: Drive over a speed bump at low speed or load the suspension in a driveway dip. Look for fender or liner contact at the outer edge.
• Brake clearance: Spin the wheel by hand and check spoke-to-caliper spacing. Paper or clay can help reveal tight spots.

Using the Wheel Interchange Calculator

The calculator lets you compare “Wheels from (donor vehicle)” versus “Installed on (your vehicle).” For custom setups, adjust rim diameter, width, and offset, plus tire section width and aspect ratio. When you change rim diameter, the tool updates tire diameter in the comparison so you can keep things balanced.

• Start with the OEM baseline above as your “Installed on” reference.
• Enter a donor wheel or use “Custom wheel size” to try a new width and offset.
• Watch inner clearance and outer position. That’s your quick mental model for rub risk.
• Adjust tire size to keep the overall diameter near stock for a calmer speedometer and ABS feel.

Example change, just to visualize

Say you are comparing 18x8.5 ET35 to the OEM 18x8.0 ET45. Width grows by 0.5 inch, which adds about 6.35 mm to both inner and outer halves. The offset drops by 10 mm, pushing the wheel outward by 10 mm. Net result is roughly 16 mm more outer poke and about 4 mm more inner clearance. That might look great, but still confirm brake clearance and fender room on your car.

Safety-first notes

• Torque your lug bolts in a star pattern using the torque value from your owner’s manual. Recheck after a short drive.
• If you use spacers, pick hub-centric spacers sized to 66.6 mm with proper lip support. Longer, matching-seat lug bolts are often required.
• If any OEM spec on your car is different from the table, set the calculator to your exact baseline before comparing.

Helpful tools

• 1/2 inch drive torque wrench
• 66.6 hub-centric rings
• M14x1.5 lug bolts (match the seat style to your wheel)
• Wheel hanger guide tool M14x1.5

Bottom line

The 2008 S4’s baseline is 18x8.0 ET45 with 235/40R18, 5x112, and a 66.6 mm hub. Use that as your mental model in the calculator. Confirm center bore support, offset and width changes, tire diameter, and bolt engagement. Do a quick on-car test for clearance. That set of checks turns guesswork into confidence.