power assisted steering (PAS) as standard. B6 S4 brakes consisted of radially ventilated disc brakes front and rear. The front discs are sized at in diameter by thick, and are clamped by Continental Teves-ATE FNRG-60 single-piston sliding brake calipers. The rears are by , and again use single-piston sliding calipers, with an integrated cable-operated hand brake mechanism. A Bosch ESP 5.7 Electronic Stability Programme system, complete with Anti-lock Braking System (ABS), Electronic Brakeforce Distribution (EBD), Emergency Brake Assist (EBA), Electronic Differential Lock (EDL) and Anti-Slip Regulation (ASR) - also known as traction control system, coupled with a dual-rate tandem vacuum servo provided the brake actuation. Standard wheels were 'Avus-III' die-cast aluminium alloy, 8.0Jx18H2 ET45 in size, and shod with (eXtra Load) high performance tyres, with factory supplies being either Continental SportContact2 or Michelin PilotSport PS2. B6 body & interior Discrete lower door trims, along with the now trademark Audi 'S' model vertical-emphasis line grille, and solid aluminium (later replaced with plastic covered by aluminium) exterior door mirrors, and S4 badging front and rear are all that visually distinguish the S4 from its related A4 brethren. In the interior, front and rear Recaro seats (fronts fully electric with the option of heated seats), as well as S4 logos in the instrument panel and door sills complete the detail. B7 (Typ 8E/8H, 2005–2009) The Audi B7 platform Audi S4 quattro, based on the Audi B7 A4, debuted in late 2004. Although Audi classifies it as a new car, the differences between it and the outgoing B6 S4 casually appear to be primarily cosmetic, and is still classified by the internal designation: Typ 8E (although with revised sub-designations - saloon: 8EC, Avant: 8ED, and Cabriolet: 8HE). It has the same 4.2-litre V8 engine (identification code: BBK) as the B6 S4, producing a power output of at 7,000 rpm, and torque at 3,500 rpm. There are a few mechanical changes, such as revised springs and dampers and, from model year 2007, an updated Torsen T-3 automatically biasing centre differential, featuring a 'default' asymmetric 40:60 front-rear torque split on manual transmission models, along with the later Bosch ESP 8.0 Electronic Stability Programme and gloss black painted brake calipers. The 'Avus-III' wheels now became an option, and were replaced by a standard offering 8.0Jx18 inch 'S-design' 7-spoke forged alloy wheel. Bose sound system is now standard, whereas it was optional on the B6 S4, and an