(part 2 sliced in half to fit on bmw digest)
>In our last episode we discussed how to make the car go faster by improving
>the driver (you!). In this part we'll delve into some technical details about
>suspensions: how and why they make your car go faster.
>
>One of the reasons we bought BMWs in the first place instead of Camaros or
>Corvettes is that handling is important to us. At least, I hope so. And one
>of the things that BMWs do really well is handle. If so, why is it people
>like me and Carl Buckland are forever modifying our suspensions to get
>better handling?
>
>Two reasons: to go faster and to have more fun. While it's true that races
>are won on the straightaways, it's also true that all other things being
>equal, the car that can get through the twisty bits faster will get lower lap
>times. As for fun, many of us like the responsiveness that a taut suspension
>gives our cars. We find them simply more fun to drive.
>
>What's wrong with the stock suspension on my M3, you ask. Good question,
>Bucky. The engineers that designed your car had to factor in many goals in
>their design. First, the car must be safe. Since BMW can't make you pass
>adriving test before you get to buy your shiny M3, they have to assume that
>not all their customers are excellent drivers. Thus they design in some
>understeer so if you get in trouble the car will be more recoverable. Second,
>the car must be comfortable, so relatively soft springs and shocks are fitted
>to keep the ride quality high. Third, the car has to be competitively priced,
>so they have to select a suspension design and components that are
>affordable. Many other factors, from the size of the engine compartment, to
>ground clearance, ease of maintenance, and tire longevity have to be figured
>into the final design. Needless to say, that design, sterling as it is, is a
>compromise.
>
>This year BMW will sell 100,000 cars, and most of them will still be running
>on a stock suspension 10 years from now. So BMW must be doing something
>right. For some of us, however, we want to optimize the design towards some
>specific goals. That's where modifications come in, and that's where it gets
>complicated.
>
>For every modification to your suspension you make to improve handling,
>there's some tradeoff that comes along. Reduce the ride height and there goes
>your ground clearance. Pretty soon you'll rip some overpriced hunk of plastic
>off the bottom of your car as a result. Increase spring rates and ride
>quality goes out the window. Five miles of bad road and your tailbone will