Building A Better Bimmer - Tuner Tech

Even BMW recognizes Southern California's infamous Mulholland Drive as an excellent road - well, BMW's bike division does. While we seriously doubt the manufacturer would approve of us fine-tuning our latest Bimmer buildup on a road that BMWMotorcycles.com recommends, we're going to do it anyway.

There is a point, though, to our spirited driving on public roads, and it's to transform our lethargic E46 323i into something it should have been originally. We're doing that by dialing in two parts of the car the factory forgot about: the suspension and the brakes. In the August '04 issue we rectified most of the car's suspension issues with UUC Motorwerks' Stage 3 shocks and springs and doubled those with forged 19x8-inch DPE R16 wheels and a set of 245/35 Kumho Ecsta MX tires.

Granted, those upgrades cost over $4,400, but our 323i's torpid demeanor was transformed into something with more verve. The next problem was stopping.

In case you don't grasp the connection between better suspension and the need for upgraded brakes when no more power has been added, let us explain. Better suspension means you can drive faster through a turn, carrying more speed onto the next patch of straight road, and consequently obtain a higher velocity by the time you reach the next series of turns. To navigate the upcoming turns, you need to slow the car or else you're going to plow off the road. A couple of high-speed corner entries and you'll soon feel the brake pedal soften, pressing closer to the floor with every jab. This phenomenon is called brake fade, and it's something most 3,100-pound sedans suffer from. With our suspension upgrades, the smell of baking brake pads permeated the cabin, so we knew it was time to junk the factory stoppers and bolt up something else.

The Stop Tech Big Brake Kit was chosen for several reasons. Mainly, StopTech goes further than some big brake manufacturers when it comes to caliper-piston sizing. StopTech's kits utilize sequentially sized pistons (meaning the leading piston in the caliper is smaller than the trailing one). This should all but eliminate the nose of the brake pads digging into the rotor when you depress the brake pedal, which leads to even clamping pressure exerted on the pads. That ultimately results in better utilization of the pads, more efficient braking, and longer component life.

StopTech's big brake testing also includes making sure the car isn't receiving too much front or rear braking with its kit installed. While you can dial in front and rear brake bias with a bias valve, most people won't do that. So the company spent time developing its kits for each car, and as it turns out, an E46 323i needs a 30mm leading piston and 36mm trailing one.

The result of all this toil is a car that turns and brakes at an even rate - the front shouldn't wash out and the rear won't lock up.

To add panache to the rear,... 

   

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To add panache to the rear, we installed cross-drilled StopTech units and Axxis pads. You can also upgrade the rear brake lines to stainless steel for $60.

While we were upgrading the front brakes, we tossed on a set of StopTech's cross-drilled rear rotors and Axxis Ultimate High Performance brake pads. Even though it wasn't completely necessary to upgrade the rear, we wanted to match the look of the rotors front to rear.

For the install, we headed to EF1 Motorsports in Signal Hill, California. The crew is familiar with BMWs, old and new, and is pretty good at turning wrenches on them. While a big brake upgrade is some-thing you could probably do at home, we recommend you head to a competent shop if you're nervous about working on the brakes. Remember, they are a vital part of what stops you from plowing into something.

To measure braking distances,... 

   

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To measure braking distances, we used an Escort Passport G Timer GT2 from RadarBusters.com. It requires no setup; just plug 'n' play.

For our tests, we did a series of 60-to-0-mph brake runs measured by an Escort Passport G Timer GT2. The GT2 measures everything from 0-to-60 and quarter-mile times to g-force and peak horsepower, without calibration or hardwiring to your car. The GT2 costs $249.95 from www.radarbusters.com, and with it we were able to test the stock and after-market brakes like anybody could.

The braking numbers reinforced exactly what we already knew about big brakes. The stock system, while good, started to fade after three consecutive 60-to-0 stops. With StopTech's 332x28mm front rotors replacing the puny factory 287x22mm units, the braking distance was reduced by a couple of feet. The major difference came after five brake runs where the StopTech setup didn't show any fade. In fact, the longest run of all five passes was the first, which was probably because the pads were cold - once they entered the ideal heat range, the braking distances were consis-tently around 120 feet.

On canyon roads, the 323i can now dive-bomb turns without the driver concerning himself with brake fade. We've discovered it's nearly impossible to get the StopTechs to fade through canyons - for that we'll have to try the track.

We've spent $6,761.95 getting the suspension and brakes to where we think they should be. That may seem like a lot, but considering the same year's E46 328i cost $6,410 more than the 323i (and this car can now outperform a 328i through the turns), we don't think the cost is as astronomical as it may first appear.

When attaching the brake line...        read full caption When attaching the brake line to the StopTech caliper, make sure the order is 14mm banjo bolt, copper washer, brake line, then copper washer; then tighten to the caliper at about 12 lb-ft.	While installing the front...        read full caption While installing the front rotors, ensure the vanes inside the rotors point toward the back of the car when the rotor is viewed from the top to provide the proper cooling effect.	When installing pads, remove...        read full caption When installing pads, remove the bridge bolts and bridge, slide the pads into place, and reinstall the bridge. Make sure you don't strip the bridge bolts, or you could lose your pads - and that's very bad.
The rear StopTech rotors aren't...        read full caption The rear StopTech rotors aren't directionally vented. EF1 Motorsports recommends you install such cross-drilled rotors so the top half of the spiraling holes curve toward the back of the car. Before you install any rotor, clean it with either soap and water or brake cleaner to remove the rust inhibitor from the rotors.