The off the shelf spring specs on the BC Racing BR Series Coilover BMW 3 Series 2006-2013 (I-18-BR) are:
Front spring rate: 8kg
Rear spring rate: 12kg
The BC Racing BR Series is our most popular suspension package. Equally at home on street and track the BR Series offers the best of both worlds with ride height and damping adjustability. Damping is adjusted simultaneously and height is adjusted independently of piston and spring stroke. The BR Series offers a minimum 2 inch drop* as well as 30 levels of damping adjustment. Assembled by hand in our facility, each application undergoes stringent quality control protocols to deliver the best possible suspension product to the consumer. Our most added value to our customers is the option to customize spring and damping rates to your to your individual preference. The BR Series is not meant as an entry level suspension setup but as a versatile setup that excels across a number of automotive disciplines.
*Extreme drop separate