Cheer up, cheapskate. You've already got all the bikes you'll need to sample the sport. With a few minor alterations, either your mountain bike or your road bike will be suitable for cyclo-cross — though you'll probably want to leave the track bike in the garage.

Which of the others should you use? A doctored road bike will give you more of the "feel" of 'cross, but a mountain bike is easier to set up. However, since 'cross, for most of us, is a sideline — a way to stay fit and build strength for road or mountain biking — consider using whichever bike is your primary racing machine.

Converting a road bike

Get rid of the bottle cages — you're going to be shoving your shoulder through that main triangle for run-ups — and lose the frame pump and saddle bag, too. Remove the pedals and replace them with whatever you're using on your mountain bike. Don't forget your off-road shoes.

At the other end of the bike, swap your corncob for a 12-27 or 11-28 and your slicks for knobbies. Sewups are best, but clinchers will do, if you don't mind the occasional pinch flat (a spare wheelset for the pit is an excellent idea for such occasions). Vittoria Mastercross and Normal Cross are excellent all-conditions fronts, with a file tread pattern; Wolber 28 Cross Extra or Clement Grifo Neve are all-purpose rears, with an arrow-and-block tread. Everyone I've seen on tubies lately is using Tufos, either the real deal or their tubular-clincher, which is said to blend the best of both worlds. If you're going with clinchers, the Vredestein Campo, Michelin Jet and Sprint, and Ritchey SpeedMax are great. I like Continental's Twister Pro, too, but it's a bit heavier than the others.

Your 53/39 crankset will do as is; snug your front derailleur up to the big ring to keep your chain from bouncing off. If you've got $25 to spend on a 48-tooth outer ring, and time to rearrange your front derailleur, replace that 53.

STI and Ergopower are the standard in 'cross, so you're good to go here, unless you're still shifting from the down tube. Cheapskates, Luddites and gram counters can go for bar-end shifters, which are nearly indestructible and feature a friction option when conditions get iffy, and and aero' brake levers.

Consider rearranging your brake cables so that your rear brake is on the left; it's nice to be able to modulate your speed when you're rumbling up to a barrier in a half-dismount, with your left hand on the bars and your right on the top tube. You may also want to add a set of the top-mounted brake levers from Empella, Salsa, Radius or Tektro, which let you brake from the bar tops. Your road pads will probably suffice for dry conditions. And when the going gets gooey, the minimal tire clearance of a road frame is going to set you afoot in short order anyway.

Radically converting a road bike

If you've got a beater bike to experiment with, ask a frame-builder to add cantilever braze-ons front and rear. You'll appreciate the extra braking power cantis provide in foul weather. Don't forget cable hangers and barrel adjusters for your headset and seatpost binder bolt.

While the torch is hot, have your frame-builder move your old brake bridge up a touch for more rubber clearance. Think about clipping the chainstay bridge out while you're at it. Finally, you might add a "brake booster" to minimize any extra flex resulting from your frame surgery.

Converting a mountain bike

Mountain bikes are legal in American 'cross, and this may be the best way to get your feet muddy. Pull off your bottle cages, saddle bag and pump. Do the same with the bar ends, which are illegal pretty much everywhere, no matter whose racing license you carry. Swap the fat rubber for something a little skinnier (26x1.5"-1.7"), which will lower your rolling resistance while increasing your tire clearance.

If you want more of the feel of 'cross, you can reverse your brakes, and trade your straight bar for drops. But you're talking a new stem, bar, shifters and brake levers — big bucks and a ton of work. And that's not why you're reading this, is it?