The first thing Tim Johnson remembers hearing from the son who had gone unexpectedly airborne that dreary August afternoon seven years ago in southern Canada, a 12-year-old bucked from his 250cc motorcycle like a clueless bull rider, was that he could not feel his legs.

Michael Johnson could not feel his legs, he later learned, because there was no way of feeling them. At the moment his chest, hurtling toward a wooden fence at almost 80 mph, met the handlebars of a dirt bike that refused to go any farther, the paraplegia was immediate. His back was broken. The T5 and T6 vertebrae, like the panels of the fencing in his wake, were in pieces.

Johnson knew none of that when he found the next few words to say to his father. He knew only that the race was over, and that he had lost, and that half of his body was now failing him.

"But immediately after that," Tim Johnson recalled earlier this week, "he made the comment that he didn't want to quit racing."

Neither father nor son could have known then how possible that dream was, nor could they guess it would ever get much grander. But it was, and it did.

On Tuesday, having signed the last of several dozen autographs as the sun's fading rays splashed across the Baltimore Marriott Waterfront, Johnson sat in his wheelchair and explained what he hoped this weekend's Grand Prix of Baltimore would bring. Of course, there was the possibility of a win today, the first of his USF2000 season and a sure-fire salve to an uneven campaign in the lowest rung of IndyCar's Road to Indy ladder. But a win would only feel good, he knew, if it meant he was one step closer to the Indianapolis 500, a mecca of motorsports and a racetrack no paralyzed IndyCar driver has ever before circled.

"The zone I'd like to be in right now would be a zone where, when we're out on the track and we're waiting for something to happen, the light bulb just clicks and you really get into that rhythm where you're quick in the good laps, you're at podiums, you're winning races," Johnson said. "That's what I'm waiting for right now."

So, how does a teenager forced to trade one two-wheeler, a motorcycle, for another, a wheelchair, end up with aspirations of being the next Mario Andretti?

To start, you can blame what Johnson reverently calls "the cushion." That's biker speak for a deep pea gravel, ideal for flat-course racing, which was what Johnson was doing in Sarnia, Ontario, the day his career plans changed irrevocably.

Racers like "the cushion" because it's fun to drive on, slide on, win on. Rain changes that, however, and when the drenched half-mile horse track Johnson was zipping around on Aug. 13, 2005, began to rebel, Hiawatha Horse Park spit back chunks of dirt and tiny stones that stuck to his helmet visor.

Johnson could see the white flag as he tossed away the last of his debris-splattered tear-offs, a plastic film that covered his visor and allowed for a clean line of sight. He remembers shooting into Turn 4 of that five-lap heat race. He was in third place, he recalls, and he knew he could pass the guy in first with an inside move. But his shield was browning by the second, his vision muddled by the splotches spraying back at him, and so he wiped it one last time.

"I remember this vividly," Johnson said. "Something happened."

He still doesn't know what made his bike break for the hay bales that lined the track's outskirts. It was probably a bad rut, Johnson reasoned Tuesday, or maybe a rear tire wheel. Whatever it was, it forced man and machine into an abrupt 90-degree turn right, and "I just pinged all the way to doom," Johnson said.

He broke his collarbone, right ribs, left ankle and left leg. He bruised his tailbone. A pressure sore he developed soon became infected. It wasn't until after nearly a half dozen surgeries, 20 screws and a year of low-octane rehabilitation that he got the all-clear from his doctor. When he did, he found a pool and went swimming.

A custom-made, green Merlin go-kart arrived on Christmas Eve in 2006, and after the snow cleared and the racing season started around their Mount Morris, Mich., home, Michael and Tim headed for Indiana's Michiana Raceway Park.

"Several of the fathers were making comments to me at the time that they just were amazed at how fast he was driving and were constantly asking me how many years he'd been driving go-karts," Tim said. "My answer back to 'em was, 'Well, I dunno. We've got 10, 15 minutes in it now.'"

Said former coach Grant Maimam: "Racing itself is a series of hurdles that you need to overcome with maximum efficiency. Being in a chair was just another hurdle."

There's a lot more mileage on Johnson's career these days, and a lot more checkered flags, too, after he plowed through lower-tier four-wheel classifications like the Junior SuperCan class, Rotax Junior class in Michigan and, most recently, Skip Barber formula car series.

His reputation grew, and the sponsors he needed to survive in the USF2000 series came before long. A manager, Matthias Czabok, signed on as well. He was also skeptical of the handicapped racecar driver. Not for long.

"He'd seen Michael riding around in his wheelchair … and then, all of a sudden, Michael is strapped into the racecar. And he wasn't paralyzed anymore," Tim Johnson said. "He was a racecar driver."