Now insert the H&R damper and use the jack to again raise the suspension arm so you can bolt the arm to the hub again (pic 13). Finally, bolt the damper into place top (pic 14) and bottom and refit the trunk liner.
It's suggested you set the lower spring perch in its middle setting, to give you a starting point when its time to adjust the ride height. Although this works in principle, in reality, the rear of our 135i sat really high. We ended up winding the perch all the way down, using a 10mm Allen socket in the bottom of the threaded shaft. This lowered the car 1 3/4" but we may need to raise it when we fit our 19" wheels next week.
Fitting the Front Suspension
Sam started by disconnecting the ABS, brake pad and headlight sensors from the front suspension strut. This is done to prevent them being stretched when the suspension sags during the upgrade process. He also supported the brake hub with a jack to avoid it dropping suddenly when the strut is loosened, causing damage to brake lines or fingers.
The first job is to remove the sway bar end link from the hub using a 16mm socket and an open-ended wrench on either side.
Next, an 18mm socket and open-ended wrench are used to remove the pinch bolt that secures the strut in the hub. Once this bolt is removed, he used a small chisel to gently pry the two sides of the hub apart, allowing the strut to be pulled from the hub.
The limited suspension movement meant the hub wouldn't drop enough to free the strut, so Sam removed the three 13mm nuts that secure the top of the strut into the suspension tower - you can do this without removing the strut tower brace if you use a 13mm open-ended wrench on one of the nuts (pic 15).
This allowed the strut to move more freely, but the suspension still didn't have enough movement to free the strut, so the steering arm linkage was undone. With some more jiggling, the strut finally came loose.
With the strut out, the top mounts are needed for the H&R replacement (although not the plastic sleeve or bump stops). Releasing the top mount is a dangerous task since it holds the coil spring under tension. You must safely compress the coil spring using a spring compressor before you attempt to undo the 21mm top mount nut (pic 16).
The H&R dampers are labeled Left and Right to help you, so place the top mount assembly on the new strut once the red H&R coil spring is in position. The body of the strut is threaded and the spring sits on an anodized perch that can be screwed up or down the body to change the ride height. Again, it's suggested you place the perch in the middle position on the thread. We did this but had to raise the front slightly to get the car where we wanted it once the wheels were fitted.
When refitting the top mount, you don't need to compress the spring again. The 22mm nut supplied by H&R will fix everything into place once it's tightened down (pic 17). However, do ensure the spring is properly seated in the top mount before you proceed. Sam also suggested you align the narrowest portion of the spring with the area adjacent to where the wheel will be. This will give you extra clearance if you opt for wider tires.
While reassembling the H&R coilovers, it was noted that the 135i strut bolts to the dead center of the top mount. On previous BMWs, such as the E46 3-series, the bolts were offset, allowing some degree of negative camber to be added by simply rotating the position of the top mount. However, the 135i will require an additional camber plate in order to gain negative camber for improved cornering ability (although it does increase tire wear).
The OE strut has two locating pins to ensure it's refitted correctly to align with the sway bar, steering, sensors, etc. However, the H&R damper doesn't have these so observe its position before removal (although you are able to rotate it slightly before bolting everything in place).So refit the front strut by inserting the bottom into the hub (pic 18). You may want to lube the strut tube and pry the hub open to help this process. Then use a crowbar to lever the suspension down so the top of the strut clears the fender. The whole assembly now needs to be lifted into the suspension tower (pic 19) so the three nuts can be secured to the top mount (the top mount rotates to ease alignment and there's a locating pin to ensures the mount is in the correct position).
Provided the strut is positioned correctly, you can now attach the sway bar end link, but don't tighten it. Now use a jack to raise the brake hub and ensure the strut is properly seated. Recheck the sway bar link. Now tighten the pinch bolt to hold the strut before tightening the sway bar, refitting all the sensors and reconnecting the steering.