NEW YORK - Regardless of what happens in Saturday's Wood Memorial at Aqueduct and the Santa Anita Derby, the theme of this year's road to the Kentucky Derby will continue to be the road itself - specifically, what that road is made of.\nDerby aspirants are by definition surrounded by questions until the main event, since they are young and developing horses who rarely have tried the distance or lined up against as good or crowded a field as the one they must face on Derby Day. This year, though, that inherent confusion is being amplified by an unprecedented series of questions raised by the surfaces over which they have been running.\nConsider the surface-related issues involving virtually every early favorite for the classics:\n* I Want Revenge, the odds-on Wood favorite, looked like nothing sensational winning 1 of 6 starts on synthetic tracks in California. Switched to dirt for the Gotham Stakes, he posted an explosive 8 1/2-length victory. Was it the switch to dirt, or were those other seemingly slow horses in California a lot better than they look?\n* Quality Road won the Florida Derby over a dirt track that Todd Pletcher, who trains runner-up Dunkirk, called unfairly biased toward front-runners. Did Quality Road move to the head of the class - and possibly deny Dunkirk a Derby starting berth - because he's the better horse or because of the racetrack?\n* Friesan Fire looked like an overachiever clicking off stakes victories against suspect fields in Louisiana, then caught a sloppy track in the Louisiana Derby and looked like a worldbeater scoring by seven lengths in fast time. Was it the slop or his true colors?\n* The Pamplemousse and Pioneerof the Nile, the dominant co-favorites in the Santa Anita Derby, have made a combined 12 career starts - 10 on California synthetics and two on grass. Whatever they do Saturday, what in the world is a horseplayer to make of their chances when they try dirt for the first time in the Derby? The same question will probably apply to next week's synthetic Blue Grass Stakes, where the leading contenders include horses who have either failed against top company on dirt (Hold Me Back) or never tried the natural stuff (Mafaaz).\nWelcome to the ongoing science-fair experiment that American racing has become since the introduction of synthetic tracks, which account for a sliver of the races run in the United States but a greater share of top-class events because Keeneland and Southern California now race on these new surfaces.\nWhen the synthetic tracks were introduced, they were supposed to play just like dirt but be safer and easier to maintain. By my count, they're 0 for 3. They have proven no safer than the best-maintained dirt tracks, they have been an ongoing maintenance nightmare, and no reasonable person can argue that horses show the same form over both surfaces.\nForget about the unpredictable 3-year-olds for a moment - just look at the most recent runnings of the world's most prestigious main-track races. In last year's Breeders' Cup Classic, run for the first time on a synthetic track, European grass milers ran one-two while Curlin, the world's best dirt horse by open lengths, couldn't even hold off Tiago for third. In last week's Dubai World Cup, Well Armed pulled an I Want Revenge, returning to the dirt after 11 in-and-out synthetic-track efforts and crushing an international field of millionaires by 14 lengths.\nThe folksy old racetrack maxim that "a good horse can run on anything" has been further exposed as the hokum it always was. What we're seeing today is the same thing that happened with the proliferation of grass racing over the last two generations. With a few remarkable exceptions like John Henry, good horses are usually much better on one surface or the other. When Cigar went from allowance-race punching bag to Hall of Famer when switched from grass to dirt, it didn't mean that the horses he couldn't beat on the grass now needed to be re-evaluated as potential champions.\nPerhaps that's the way to view a Pioneerof the Nile, who looks and runs like a horse better suited to grass or synthetic rather than dirt racing. The fact that he beat I Want Revenge twice on synthetic doesn't necessarily mean he's on the same planet as that colt when it comes to dirt. If he wins the Santa Anita Derby, though, he will get plenty of support in his dirt debut on Derby Day, primarily because of two victories over I Want Revenge that might as well have happened on the dark side of the moon.