The stock shock absorbers (struts) on your BMW are a compromise between performance (meaning braking, handling, and acceleration) and ride comfort. While the factory setup has a strong performance bias, it’s possible to do better. One way you do this is by installing coilovers.
Swapping the stock struts for coilovers technically could be completed by a talented DIYer, but is best left to professionals. Proper installation, alignment, and tuning of the suspension is all part of the job. The technicians at EurAuto have completed many coilover conversions on BMWs and other European an exotic cars.
Know the Difference
At each corner of your car there’s a spring between the body and wheel. There’s also a damper, called a shock absorber, or just “shock”, that governs how fast the spring moves.
When combined, like they are on the front of a BMW 335i, the spring and shock assembly is termed a strut. A coilover is a type of strut that offers the driver/mechanic much more control over how the assembly performs.
Adjusting Ride Height, Compression and Damping
Ride height is set by a ring around the shock that locates the bottom of the spring. The shock body is threaded so the ring can be screwed up and down. This shortens or elongates the spring and raises or lowers the car body.
Lowering the ride height brings down the center of gravity, which improves handling, and reduces airflow under the vehicle. Plus, some people think a lower vehicle looks better.
The shocks in coilovers have adjustable valves for controlling the rate at which the assembly moves. This softens or stiffens the ride and has a big impact on acceleration, handling and braking. (Stiffer is better for faster track or autocross times.)
The Coilover Installation Process
While the spring and shock arrangement at the rear of a BMW 335i isn’t technically a coil over, the back spring is inboard of the shock, it’s important to upgrade all four wheels and not just the fronts. If you don’t do this you won’t get the adjustability and improved performance which is the reason for doing the job.
At the rear the spring and shock are mounted between body and lower control arms. Each arm is unbolted at the wheel end and lowered to allow removal of the old components. Installation of the new parts is the reverse.
At the front the top of the shock and the spring are located in the strut tower and the bottom of the shock is fixed to the wheel via a sturdy knuckle. Removal starts by undoing the assembly at the strut tower, after which the shock is withdrawn from the knuckle. Installation is the reverse procedure.
Ride Height Adjustment
When installing the coil overs it’s essential to set the ride height the same at each corner. If you don’t do this the vehicle will not sit flat and level and braking and handling will be compromised.
Once the job is complete, ride height can be adjusted again to deliver the setup the driver is looking for.
Having upgraded the suspension, the vehicle must receive a four-wheel alignment. Skipping this step will lead to uneven tire wear and again, compromised handling and braking.
Come to EurAuto For Your BMW Repair Needs
If you’re looking to elevate the already impressive handling of your BMW, replace the factory struts with coilovers. The team at EurAuto is always happy to do performance modifications of any kind to your BMW. To schedule an appointment, call 214-552-4194 or use our online scheduling form.