Will a suspension seatpost screw up my biking geometry?

A: Doesn't alter seatpost height at all, Preston. A suspended post is simply a replacement for the stock, spine-buckling seatpost. You install it on the bike, adjust it to your normal riding height, and off you go. The only time the seatpost yields an "abnormal" seat height is when you've hit something big and hard and the post compresses. But that's only for a split-second, of course.

I've used suspended seatposts for three or four years and am a big advocate of them. Most (not all) of the advantages of a true dualie, but they're lighter, cost less, and are easy to upgrade. I've used the U.S.E. post, now called the U.S.E Alien ($139). It combines a spring with a rubber bumper for good bump-absorbing capability and fast return. Heavy or light riders can replace the bumper with one better suited to their riding style and weight. Installation is easy-it's just like replacing a regular seatpost, the only difference being that you'll probably also need a plastic shim that goes inside the seat tube.

Rockshox also makes a good suspended post that sells for only $70, though it lacks the spring of the U.S.E. post and is rubber-only. Still, it's an inexpensive, worthwhile upgrade.