“There are literally dozens of suspension options for the M3, but Dinan has a complete package and its reputation made me comfortable that it would actually improve my car,” Sweetwood says. “It wasn’t the cheapest option, but I’m thrilled with the improvement in street ride and handling on the track. It’s hard to achieve both, but the Dinan suspension does it.”

Indeed it does. The car’s handling is much sharper and more agile than stock, yet it surprises me by feeling more fluid and compliant than my stock E46 wagon over New Jersey’s poorly maintained public roads. Fewer sharp jolts reach the steering wheel or seat bottom, yet body control is impeccable. On real American roads, which are far from Bavarian perfection, the suspension tuning achieved by Dinan or Alpina is vastly preferable to the rather harsh factory settings.

The improvements to both handling and acceleration can be attributed not just to the better suspension components but also to the remarkable reduction in unsprung weight achieved by replacing the stock wheels and brakes with far lighter aftermarket parts. We’ve remarked on this principle many times, most frequently when discussing Dinan BMWs fitted with that company’s lightweight wheels as well as its supple suspension. It applies here, as well, even though Sweetwood opted for a set of TR Motorsports MT1 wheels rather than Dinan’s forged alloys.

At 18 inches in diameter rather than the 19 inches of the Dinan wheels, the 8.5-inch TR fronts weigh just 18.5 lbs. each while the 9.5-inch rears weigh 19.0 lbs., a few pounds per corner less than the stock wheels and at least one pound less than the 20.0-lb. Dinan hoops. Reducing wheel weight by any amount will have a dramatic effect on handling, allowing the car to change direction far more easily—each wheel acts like a gyroscope, remember, and the heavier the gyro the less it wants to vary from its course. It will also aid acceleration, because it takes less power to rotate a lighter wheel than it does a heavier wheel. The reverse is true, as well, with braking similarly improved through the use of lighter wheels.

Pricey prototypes

Of course, to really improve braking requires fitting better brakes. As track junkies know, the factory brake package may be perfectly adequate for street use or even vigorous exercise on canyon roads, but track sessions will quickly bring out its weaknesses. Performance can fade, and rotors can warp and eventually crack.

Help from the aftermarket is required. As with suspension, a bewildering array of braking options is available, all offering an improvement over stock. Sweetwood wanted more than just better braking—he also wanted to reduce unsprung weight beyond the wheels. Toward that end, he engaged StopTech to engineer a carbon ceramic system like the Brembo setup available as an expensive option on Porsche and Ferrari sports cars. (In addition to owning Unique Photo, Sweetwood is a StopTech dealer through his Zeckhausen Racing firm.)

His M3 is running one of two prototypes of the resulting system, which pairs solid-mount multiple piston calipers with carbon ceramic rotors made from continuous fibers that are said to have much greater resistance to cracking than the commonly used chopped fibers in other rotors.

Up front, each 355mm carbon ceramic rotor weighs just 9.6 lbs. where the stock 325mm iron rotor weighs 19.0 lbs. Each six-piston caliper, meanwhile, weighs just 10.0 lbs. where a stock single-piston caliper weighs 17.0, resulting in a massive 32.8-lb. reduction from the front axle.