2006 Audi S4 — Sedan

The 2006 Audi S4 Sedan came from the factory equipped with 235/40R18 tires. If your vehicle has since been fitted with aftermarket or upsized wheels, your actual tire size may no longer match this factory spec — always confirm against your door placard before buying.

235/40R18

Section width235 mm
Aspect ratio (sidewall height)40% (94 mm)
Rim diameter18"
Overall tire diameter~25.4"
Revolutions per mile~794

Compare prices at:

What this size means for your Audi S4

On the 2006 Audi S4 Sedan, the factory 235/40R18 measures about 25.4″ in overall diameter with a 94 mm (3.7″) sidewall, and completes roughly 794 revolutions per mile. Its 40-series aspect ratio gives a low-profile sidewall tuned for sharper handling, common on sport trims and larger-wheel packages. In tire terms it is a passenger (P-metric / Euro-metric) size.

On a vehicle of this age, the Audi S4 may have been refitted with a slightly different replacement size somewhere in its life, so check the current sidewall — not just the factory spec — before buying.

Other 2006 Audi S4 trims

Audi S4 tire sizes by year

See every Audi S4 year & trim →

How to read a tire size

A tire size like 225/45R17 breaks down into three parts: the first number is the section width in millimeters (the tire's width from sidewall to sidewall), the second is the aspect ratio — the sidewall's height as a percentage of that width — and the number after the "R" is the rim diameter in inches. A letter prefix (P or LT) indicates Passenger or Light Truck construction; its absence usually means Euro-metric sizing.

Some trucks and off-road tires instead use "flotation" sizing, like 37X12.50R17 — here the numbers are the tire's overall diameter and width in inches directly, with the rim diameter last.

Always verify against the tire information placard on your driver's-side door jamb or your owner's manual before purchasing — tire size can vary by factory option package even within the same trim.