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Even though it’s already one of the best compact luxury sedans on the market, the B9 Audi A4 is also a great platform for modification. For a relatively small investment in parts and labor, you turn this amazing sport sedan into something even better. Here are some easy upgrades to get you started.

Larger OEM Audi wheels are an easy bolt-on

Audi's 19-inch "Rotor" wheels are a nice upgrade for the B9 A4
Audi’s 19-inch “Rotor” wheels are a nice upgrade for the B8 and B9 A4 | Christopher Evans/MediaNews Group/Boston Herald via Getty Images

Factory wheel sizes on the B9 chassis range from 17″ to 20″, so there’s a wide range of Audi wheels from other variants like the S4 that will bolt right on. Some wheels from the previous B8 chassis will also fit, provided they are at least 17″ in diameter. In fact, some of them even have a lower offset than the B9 wheels. This can widen the track for a more flush look, without having to use spacers.

Although wheels from the B7 and B6 A4s have the correct 5×112 mm bolt pattern, the hub center bore is too small at 57.1 mm, so they will not fit. With the correct 66.6 mm center bore, the B9 chassis will generally accept wheel offsets in the range of ET35 to ET45 without modification. Many Audi owners sell their stock wheels and tires when upgrading to aftermarket sets. These “take-offs” can be very reasonably priced on the used market.

Exhaust upgrades give the B9 A4 a voice

A B9 Audi S4 displayed at the 2015 Frankfurt Auto Show
A B9 Audi S4 displayed at the 2015 Frankfurt Auto Show | Odd Andersen/AFP via Getty Images

Audi went to great lengths on the B9 A4 to make the cabin a quiet and luxurious place. As a result, the exhaust system has two center resonators and two rear mufflers. Most buyers appreciate the serenity, but enthusiasts may want to hear more exhaust noise.

Thankfully, there are many options to uncork the B9 A4 and give it a bit more character. Aftermarket tuners offer turbo-back and cat-back exhausts that will bolt onto an otherwise stock car. With renowned quality and unique drone-canceling technology, AWE Tuning is a fantastic choice with multiple exhaust configurations.

Rear sway bar is an easy and effective handling mod

Most cars are set up from the factory to understeer at the limit, for safety reasons. Even with AWD, an aggressive driver can bring out the A4’s tendency to push, especially on stock tires. By upgrading to a larger rear sway bar, you can introduce more rear bias and create a more neutral setup. H&R, 034 Motorsport, and ECS Tuning are some of the top manufacturers to consider when looking for an Audi rear sway bar.

Unlike lowering springs, sway bar replacements work well as a standalone upgrade. Most are made to bolt on without additional mods, and you shouldn’t need to have the car realigned afterward. Many are also adjustable, so you can fine-tune the result. Once you install and assess the benefits, you can also lower the car later on using aftermarket springs to gain additional benefits.

With these basic modifications, a B9 Audi A4 will be even more fun to drive while retaining stock-like driveability and luxury. For many, these easy mods will provide a very satisfying result. For others, there’s an entire aftermarket full of more aggressive mods to make the car perform even better.

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