The 2009 Audi S4 belongs to an era when Audi blended all-weather confidence, understated sport-sedan character, and everyday luxury into one sharply defined package. Buyers looking at this generation often want a tire that preserves that balance rather than chasing a completely different look or feel. For the 2009 Audi S4, the primary fitment is a 235/40R18 radial on an 18-inch rim. Available choices stay within that modern performance-oriented size and focus on blackwall radial options from BFGoodrich and Nitto across several series. The key decision is less about size and more about selecting the right tire character for road use, wheel compatibility, and the way the car is actually driven.
Which Tire Size Is Right for The 2009 Audi S4
The 2009 Audi S4 uses one primary tire size: 235/40R18, a radial fitment for an 18-inch rim. The Cabriolet uses the same size, so the main choice is not between multiple factory fitments but between the available radial tire options, their series, and the wheel-width compatibility that matches your current setup.
A 235/40R18 tire uses a 235-millimeter nominal section width, a 40-series aspect ratio, radial construction, and an 18-inch rim diameter. On the 2009 Audi S4, that format reflects a modern low-profile performance tire rather than a vintage sizing system, so the emphasis is on handling response, wheel fit, and maintaining the intended stance of the car. Available choices in this size include blackwall radials from BFGoodrich and Nitto across the g-Force Comp 2 AS, g-Force Sport Comp 2, g-Force Phenom T/A, and NT555 G2 series. This size is the right starting point when the car still uses the correct 18-inch wheel setup and a performance-oriented tire is the goal.
Sub-model fitment is straightforward for the 2009 Audi S4 covered here. The Cabriolet uses the same 235/40R18 radial size, so tire selection centers on product choice and wheel compatibility rather than sorting between different factory tire dimensions.
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2009 Audi S4 Cabriolet
The 2009 Audi S4 Cabriolet uses the same 235/40R18 radial tire size as the core fitment. That keeps selection simple, with attention shifting to the available blackwall performance tire series and confirming that the current 18-inch wheels still match the tire's intended rim-width range.
The tire sizes listed on this page assume factory-standard vehicle configuration. The following modifications may affect tire fitment and are not reflected in this guide:
Suspension changes (lowering, lift kits, spring replacements)
Body alterations (fender modifications, custom bodywork)
If your vehicle has been modified from factory specifications, verify tire clearance before purchase.
Best 2009 Audi S4 Tires for Sale
Available 235/40R18 choices for the 2009 Audi S4 focus on blackwall radial performance tires from BFGoodrich and Nitto. The product grid is where to compare series character, rim-width compatibility, load figures where stated, and small differences in weight within the same overall fitment.
These FAQs focus on the 2009 Audi S4's 235/40R18 fitment, 18-inch wheel requirements, available radial tire choices, and the practical checks that matter before putting a performance-oriented collector-era Audi back on the road.
Tire Size & Fitment
What tire size fits a 2009 Audi S4?
The 2009 Audi S4 uses a 235/40R18 radial tire. That is the primary fitment for the model covered here, and the 2009 Audi S4 Cabriolet uses the same size as well.
That makes the first step fairly simple: confirm that the car still has the correct 18-inch wheel setup and then choose among the available 235/40R18 radial options. If the car has aftermarket wheels or suspension changes, check wheel width and clearance before assuming any tire in the correct labeled size will behave the same way on the vehicle.
What size rim does a 2009 Audi S4 use?
The 2009 Audi S4 uses an 18-inch rim with its 235/40R18 tire size. The tire size itself confirms the wheel diameter because the final number in the size code is the rim diameter in inches.
Rim diameter is only part of the picture, so it is still worth confirming wheel width before selecting a tire. The available 235/40R18 products are intended for a range around 8.0 to 9.5 inches wide, which matters if the car no longer wears its original wheel setup or has been changed for appearance or performance.
Does the 2009 Audi S4 Cabriolet use the same tire size?
Yes. The 2009 Audi S4 Cabriolet uses the same 235/40R18 radial tire size as the core 2009 Audi S4 fitment covered here. There is no separate primary tire size to sort through for that sub-model.
That consistency means the buying decision shifts away from size identification and toward selecting the right tire series for the way the car is used. Wheel width, current wheel condition, and any modifications still need to be checked, especially on a car that may have seen wheel swaps, suspension changes, or long periods of low annual mileage.
Choosing the Right Tire
What should I consider when choosing a 235/40R18 tire for a 2009 Audi S4?
Start with the correct size and construction: 235/40R18 radial on an 18-inch wheel. From there, compare tire series, load figures where stated, weight, and the wheel-width range each product is designed to work with.
The right choice depends on how the S4 is actually used. A car driven mainly on fair-weather weekend outings may lead to a different preference than one that sees more regular street miles, but either way the tire should match the wheel dimensions already on the car and preserve proper clearance at full steering lock and suspension movement.
What sidewall styles are available for 2009 Audi S4 tires?
The available 235/40R18 tire options for the 2009 Audi S4 use a blackwall sidewall style. That keeps the appearance clean and contemporary, which suits the understated performance character of the car.
Since the visible sidewall treatment does not vary here, the more meaningful appearance and selection differences come from the tire series themselves rather than from whitewalls, raised letters, or vintage striping. Buyers who want to keep the look cohesive should focus on correct size, proportional profile, and a tire design that complements the car's factory-era sport-luxury presentation.
What brands offer tires for the 2009 Audi S4?
BFGoodrich and Nitto both offer tires in the 235/40R18 size for the 2009 Audi S4. BFGoodrich options include multiple g-Force series, while Nitto is represented by the NT555 G2.
Brand alone should not be the only filter. It is worth comparing the specific series within the correct size, along with wheel-width compatibility, stated load capacity where shown, and the way the tire's intended character aligns with the car's use. That approach usually tells more than simply choosing by name when several modern performance radials share the same fitment.
Restoration & Appearance
Which tire should I choose for a period-style 2009 Audi S4?
A period-style choice for a 2009 Audi S4 starts with staying in the correct 235/40R18 radial size and keeping the car on an 18-inch wheel. Because the available options are blackwall performance radials, the overall look remains in line with the modern sport-sedan and sport-cabriolet character of the era.
For an appearance-focused car, the goal is usually visual proportion and restraint rather than vintage sidewall ornament. A tire that maintains the intended profile and sits properly on the wheel will do more for the car's presentation than chasing an aggressive look that changes stance or draws attention away from the S4's original design language.
Does correct tire fitment matter for a 2009 Audi S4 restoration?
Yes, correct tire fitment matters on a 2009 Audi S4 restoration because size, profile, and wheel relationship all affect the way the finished car looks and sits. The proper starting point is the 235/40R18 radial fitment on an 18-inch rim.
Even on a driver-level restoration, the wrong profile or a wheel outside the intended width range can change the car's visual balance and alter clearance. Anyone chasing exact historical presentation should also compare the current wheel and tire setup against marque-specific references, especially if the car has passed through multiple owners and may no longer wear its original-style wheel package.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 2009 Audi S4?
Yes. A 2009 Audi S4 may still use the correct 235/40R18 size on paper, but aftermarket wheels, altered wheel offsets, suspension changes, or body modifications can all affect actual fitment. Clearance is influenced by more than the sidewall label alone.
A modified car should be checked at the wheel, not just at the catalog level. Verify the wheel's true diameter and width, look for rubbing marks, and inspect clearance at steering lock and under compression. That matters just as much on the Cabriolet as on any other S4 configuration when the goal is predictable road behavior without fender or suspension interference.
What should I inspect before driving a 2009 Audi S4 on new tires?
Before driving a 2009 Audi S4 on new tires, inspect wheel condition, confirm the 18-inch rim and wheel width are appropriate, and make sure the tires are mounted and inflated correctly. It is also smart to look over suspension and steering components that can influence tire wear and stability.
A short shakedown drive should include listening for rubbing, feeling for vibration, and rechecking inflation afterward. Cars that sit for long periods deserve extra attention because old alignment issues, worn bushings, or uneven wheel condition may only become obvious once fresh tires are installed and the car is driven at normal road speeds again.
How should 235/40R18 tires on a collector-era 2009 Audi S4 be maintained?
235/40R18 tires on a 2009 Audi S4 should be kept at appropriate pressure, inspected regularly for cuts, bulges, cracking, and uneven wear, and checked for air loss if the car spends long periods parked. A low-mileage performance car can age tires out before it wears them out.
Storage conditions matter as much as mileage on a car like this. Keeping the S4 away from prolonged sunlight, excess heat, and ozone sources helps protect the sidewalls, while periodic movement can reduce flat-spotting concerns. Owners planning a longer drive should also inspect tread condition and overall tire age rather than relying only on appearance at a glance.
