BMW 135i Coupe Sway Bar Fitting - BMW 135i Project update

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Turner Motorsport (www.turnermotorsport.com) recently sent us the first pair of H&R sway bars in the country for our 135i project. Unfortunately, we hadn't anticipated the need to drop the rear subframe in order to fit them. So we retreated and regrouped for a second attempt (see Blogs at www.eurotuner.com for our first attempt, as well as the July 2008 issue of eurotuner magazine).

This time we visited the experts at BMS in Santa Ana, CA on the recommendation of TMS. The shop specializes in servicing, repair, tuning and race preparation of BMWs old and new. Their huge workshops are impressively equipped, including an area for fabrication and sheet metal work.

The owner of BMS, Chris Welch, handed us off to Chris "Junior" Chapman who would be doing the wrenching on our car. Although they estimate five hours for the job, he was confident of doing it in less if we weren't slowing him down for photos and assuming there were no sheered bolts, etc. While the front anti-roll (sway) bar is relatively simple to install, the rear isn't.

Junior contradicted us by stating, "It's easy. The set-up is just like the BMW 335i. We've done loads of them and you drop the rear subframe about 4" to squeeze it in." However, there's no way you could tackle this on a DIY basis at home. You need a lift, an axle jack, some assistance and a full workshop. Therefore, you should expect to pay a company like BMS around $500 for the installation.

The H&R sway bars (pic 1) retail for $299 front and $189 rear, but Turner Motorsport will discount them to $233 and $147 respectively if you mention eurotuner when you order.

At only 12mm in diameter, the stock rear bar certainly appeared to need upgrading, and so we were expecting great things of the 20mm H&R replacement (part number 70187). However, the stock and aftermarket front bars were identical at 27mm diameter (part number 71187), so we were curious if this would have any affect.

Front First
Fitting the front bar was a cinch. Having raised the car on a lift, Junior started by removing the plastic bellypan under the engine. It was secured by multiple 8mm bolt-head screws (pic 2).

Once the bellypan was gone, he used 16 and 17mm spanners in unison to break the anti-roll bar from its end link (pic 3). You can now undo the 13mm nuts on the sway bar bushing brackets (pic 4). There are two on each bracket, but don't take them all out immediately or the bar will fall on your head!

We placed the stock and H&R bars side-by-side (pic 5) and apart from a few kinks, there's little visual difference between the two. The aftermarket part is supplied with new bushings that are lined to alleviate the need for lubricant. Despite this, Junior lubed the bushings to make it easier to slide them over and along the bar to align them correctly. The stock brackets push over the bushings and the sway bar bolts back into place using the stock bolts (pic 6). Replace the bellypan and the front bar is complete!

Rear Ending
Having warmed up with the easy stuff, it was time to tackle the rear sway bar. As you can see in pic 7, the end links are easily accessible but the bushings are bolted to the top of the axle. This means you have to drop the rear subframe to get a wrench on top of the bar to remove the nuts.

Step one was to crimp the rubber section of the rear brake lines. This prevents fluid draining onto the floor when the lines are disconnected. You need to disconnect the lines to allow the subframe to be lowered. He used a 7/16th line wrench to undo the brake lines and stressed the importance of the correct tool to avoid stripping the threads.

On the suspension, Junior removed the 18mm bolt from the upper link that would allow the axle to drop freely.

Next, he removed 5mm bolts from an underbody trim panel in order to reach the 16mm bolts on the subframe supports (pic 8). At this point, he simply loosened these 16mm bolts so the assembly remained in place.

The exhaust also needs to be lowered, so Junior freed it from its two rear hangers (pic 9). One requires a 10mm star socket to undo the hanger, while the second needs the rubber to be prised off. You'll also need to disconnect the vacuum line (that activates the rear muffler flap to help build back-pressure at low rpm) before you drop the exhaust. The center mounts now support the system.

Step six is to remove the cross-brace from under the car by undoing the 18mm and T50 bolts (pic 10). The brace can be removed at this stage.

Step seven requires you to unclip the ABS sensor cables from the suspension to again allow it to drop without stretching. You can then use 16mm and 16mm Thin wrenches either side of the rear anti-roll bar end links to undo the bolt (pic 11).The final task is to loosen, but not remove, the four E18 subframe bolts (pic 12).

Now comes the tricky part. The axle needs to be supported by a carefully positioned jack (pic 13). Then undo all the bolts that had been loosened, and