With all the excitement surrounding the arrival of the BMW 135i Coupe in North America, Eurotuner Magazine was fortunate to have a car ahead of its official launch date. Having spent a few weeks getting used to the 300hp twin-turbo RWD pocket-rocket, we decided it was time to see if we could make any improvements with a few well chosen modifications.
To be honest, the car 1-Series Coupe is so new that not many parts exist for this application, but a call to Turner Motorsport in Amesbury, MA had an H&R Street Performance Coilover (part number 50402, suggested retail $1580, pic 3) winging its way to us. This should give us sportier handling and an adjustable ride height.
We used local California BMW specialist Evosport to fit the new parts, since it's more than a DIY task - requiring a lift and coil spring compressor, as well as some experience. So we thought we'd pass on what we learned in this step-by-step how-to guide in case you want to try it yourself and have access to the necessary equipment.
Fitting the Rear Suspension
Evosport's technician, Sam Morin, started at the rear of the car, using an E12 screwdriver bit to release the bottom of the rear damper from the aluminum suspension arm that supports the stock damper and spring. He then used a 16mm socket to undo the top mounts on the dampers inside the trunk, carefully removing the trunk lining to access them.
Using a screw jack under the suspension arm to raise the rear suspension and release the tension on the damper, a 21mm socket was used to undo the bolt that secures the aluminum suspension arm to the brake hub (pic 4). Lowering the jack slowly, you can then remove the damper and spring from one side of the car and then the other (pic 5).
With a 17mm socket, remove the bottom mount from the OE damper and transfer it to the H&R replacement damper (pic 6). You also slide the plastic sleeve and bump-stop from the top of the original equipment (OE) damper and refit these on the H&R.
The next job is to install the adjustable spring perch (pic 7) in the aluminum suspension arm since this will give you the height adjustment. To do this, remove the circlip from the threaded section of the new H&R spring perch and remove the center section of the perch (it screws off the main thread). This center section split into two pieces and you fit one half under and the other half inside the suspension arm (pic 8). Use the supplied H&R C-wrenches to tighten the two halves together, clamping the arm between them (pic 9). You then poke the threaded shaft through the top section and wind its thread into the center section (pic 10). You should now replace the circlip onto the end of the thread. Lubricating oil is supplied to allow the threaded shaft to be screwed on and off more easily.
A top spring perch is also supplied in the H&R kit. This is a simple disc and it pushes into the OE upper spring perch (pic 11). With both perches in place, you can fit the H&R coil spring and its red assister spring (pic 12). The assister simply prevents the shorter H&R black spring from dislocating whenever the car is jacked up.