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Project M3 Part 9 - Basic Suspension - Shock And Awe

We give our M3 Project Car some basic suspension tweaks and measure the improvements

By Paul Piola, Photography by Paul Piola

In part 7 of our series (et 1/09) we unleashed a usable 12whp peak with a cat-back, pulleys, throttle body and coils, then we made sure it was running cool in part 8 (et 2/09). This month, we're set to improve the car's handling.

Because our M3 is daily-driven, we initially chose not to make it stiffer or lower. An M3's stance is already fairly aggressive, and with a stock suspension the ride and handling are perfect. In fact, in '97 Car & Driver chose the E36 M3 as the best handling car over $30k, which included exotics costing more than twice as much. So the challenge would be to improve the handling without introducing too many compromises.

Before changing anything, we decided to test the car against a different set of wheels and tires. Our previous setup employed ultra-light 17x8" SSR wheels with inexpensive 235/40 Sumitomo HTR+ tires (et 9/07).

For the last two years the tires have worked well through the changing seasons in Kansas City. But how good were these all-season M+S tires for spirited drives in the warmer months? To find out, we ordered a Racelogic PerformanceBox from VBox USA.

Using GPS technology instead of standard accelerometers, The PerformanceBox accurately measures acceleration times to any distance or speed as well as lateral acceleration. The information can be viewed in real-time or logged onto the supplied memory card for viewing on a laptop. It can also display altitude, calculate wheel and flywheel horsepower, and has compass and velocity readouts as well. We'll be playing more with it as the project progresses...

For our baseline test we performed a series of passes through a 180 turn that could be taken at around 60mph in third gear. We recorded our average G-force through a defined sector as well as peak G-force. Bear in mind, this isn't skidpad testing, which takes the average G-force through a portion by calculating sector time on a flat surface. We're simply looking for the improvement with a new suspension part through this turn only.

As with dyno testing, certain factors were taken into account to maintain accuracy. That said, the same driver tested the unloaded car with the same half tank of fuel, in similar weather (40-43F), with the same tire pressures (37psi cold) on a still day.

Confirming our satisfaction with Project M3's handling, the stock setup provided moderate understeer, making it easy to throw the car around and find the grip limit. We managed to average 0.95G using our PerformanceBox, but our peak registered a spouse-scaring 1.09G

The first order of business was ordering a set of summer tires to maximize the current suspension and get more from future upgrades. For this, we mounted 235/40-17 Continental SportContact2 tires on a set of D-Force semi-forged wheels from UUC Motorwerks. At 17x8.5" they weigh the same 16 lb as our slightly narrower SSRs, and the extra width will help with grip.

Once they were installed, the car felt slightly stiffer because of the stronger sidewalls. At our test turn, the extra grip was instantly apparent, and the higher levels of grip took more testosterone to get the most from them. Keep in mind, the low air temperatures don't favor summer tires at all, and yet the setup averaged 0.99G through the turn, and a peak of 1.12G. Yet we could expect considerably more in warmer weather.

To improve the handling without compromise means not lowering the car, so we looked to stiffen the chassis. In '95, BMW supplied the "X-brace" chassis stiffener in the M3 Lightweight and Z3M to reduce body flex under hard cornering. While regular E36 M3s got a single "I-brace", their subframes were pre-drilled for the X-brace. So we ordered ours from Bavarian Autosport - our one-stop shop for all our factory BMW components.

By Paul Piola
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