Buy 2009 Audi S5 Steering Knuckle. A4, S4; Left. A5, S5; Left. From 08/13/2008 to 10/31/2009, from 08 - OEM Audi Part # 8K0407253R (8K0-407-253-R, 8K0407253G)

Housing. Steering knuckle.
A knuckle used on a Steering axle that has no additional components attached.

Steering Knuckle

Fits A4, A5, Q5, S4, S5

A4, S4; Left. A5, S5; Left. From 08/13/2008 to 10/31/2009, from 08/13/2008 to 10/31/2009. From 12/9/2008 to 10/2009, Cobapress. Q5; Left. TO 10/2009, Cobapress.
Steering Knuckle - Repair or Replace
The steering knuckle in your 2009 Audi S5 may need to be replaced if it has become damaged or rusty, which will usually be determined during a related repair.