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.
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.
Before we started, Sam had measured the height of the car. Once the OE 18" wheels were refitted, the car was lowered and we measured again. At this stage, we could see what needed to be done without measuring. The rear was too high and the front too low.
It's possible to adjust the H&R spring perches without removing the wheels again, so Sam started on the rear. He lowered it by using a 10mm Allen socket in the bottom of the threaded shaft, as we said (pic 21). It's all about trial and error but after a couple of attempts the car was lowered to where we wanted it - which turned out to be the maximum amount the rear spring perches would allow the car to be dropped. After measuring we discovered it was 1 3/4" lower than the stock ride height. It's left the tires nicely tucked under the fenders.
Conversely, the front needed to be raised. This was achieved by turning the adjustable perch on the threaded strut using the C wrenches supplied by H&R (pic 20). Unlike the rear, the thread on the strut is very fine and moving the perch one inch will alter the ride height approximately one inch. So we had Sam raise the car about " so that it now sits 2" lower than a stock 135i. (see before and after pics 1, 2)
At this height, the car looks significantly more dramatic and sporting. And despite the reduction in suspension travel, we're delighted to report the ride quality remains exceptionally good. It certainly doesn't crash into potholes as some aftermarket suspensions can do. It also controls the car in corners more effectively, although we anticipate fitting larger sway bars in the future to replace the thin OE bars.
1 - Stock Height
The only real drawback of lowering the car so drastically is that we're now scraping the front spoiler on steep driveways. And you need to slow down over speed bumps. But otherwise, it simply looks and handles better.Obviously, you don't need to lower the 1-Series as much as we've done here to enjoy the benefits. And that's the advantage of the H&R Street Performance Coilover kit from Turner Motorsport. It gives you the ability to adjust the car where you want it. Contact Turner Motorsport for a special price offer for Eurotuner readers.
2- Lowered Height
And stay tuned for the next update to Eurotuner Magazine's BMW 135i project car. We have custom wheels being built and are talking to several tuners about software and exhaust upgrades.
For those of you who have been unable to get a look at the new 135i, we've also included some interesting photos, such as a look at the flat underside of the car (pic 23), and the rather torturous route the stock exhaust takes (pic 24, 25), plus a look at the electrical equipment under the trunk floor (pic 28). There's also a close up of the axle (pic 25) and those enormous six-piston Brembo-sourced front brakes (pic 26) - the biggest ever fitted on a production BMW - as well as the rear brakes (pic 27).
Our sincere thanks to Evosport (and Sam) for the expert fitting.