Racing Line’s Sport Springs are a worldwide best-seller. Little wonder, as with the extensive test and development work that Racing Line invest in each model, your Audi B9 S4 will still ride beautifully yet with a noticeably more dynamic handling edge, plus of course the perfect ride-height. In other words, just how it should have come from the factory. If you use your Audi S4 on a daily basis and are looking to upgrade the suspension, you can't do better than Racing Line’s Sport Springs. They replace the car's four stock springs with re-engineered, progressive-rate and slightly shorter Sport Springs. The springs lower the S4 models by around 20-25 mm in order to preserve the wheel travel needed for perfect ride & handling. Go lower or stiffer than Racing Line’s springs and your car tends to bounce and crash as the dampers are mismatched to spring-rate, and the springs themselves run out of travel. The result? The vehicle's center of gravity is lowered, reducing body roll for better dynamics, whilst maintaining the ride quality and comfort of your car. Meanwhile, the car's appearance is subtly transformed. By getting rid of those nasty wheelarch gaps, it'll look like it always should have from the factory! Many experts consider suspension development to be as much an art as a science. In truth, it's a bit of both. Racing Line’s extensive development program has specified progressive rate springs to preserve the ride quality in normal use, but then stiffen the rates at the ends of the travel. This progressive-rate spring construction means the spring rate in the middle of travel is very similar to standard. It's only towards the end of the spring's travel (so, when braking or cornering hard) that Racing Line have engineered the spring to stiffen up. It's this progressive-rate spring design that is the secret to such good ride quality combined with dynamic performance. The Sport Springs are developed to be fully compatible with cars fitted with Audi’s switchable ACC (adaptive chassis control) dampers. Racing Line’s Sport Springs are high quality, European-made springs, from the same factory that produces many of the OEM springs. This should first upgrade to make to your car; give it the ride-height it deserves!