To properly fix a flat bicycle tire, you gotta be willing to bleed. That is what Matt Beverley, a mechanic at Horizon Cycles on York Road, told me this week. He said I had to seek out the culprit, the cause of the flat, by running my fingertips along the interior of the punctured tire, exposing myself to potential puncture wounds. This, he said, prevents the thorn or nail from striking again, taking out the replacement tube, a few miles down the road.

"Fixing a flat is like doing a brake job on your car," said Beverley, who has been a bicycle mechanic for 12 years. "If you haven't bled a little, busted your knuckles working on the brakes or pricked your finger looking for what caused the flat, you don't feel like you've done the job."

I sought advice from Beverley because, like a lot of things in our increasingly complicated life, the once straightforward task of fixing a flat bike tire had grown more daunting. At least to me.

Eons ago when I was a kid pedaling a Western Flyer that had a foot brake, repairing a bicycle tire was a job that my dad could knock off in a few minutes. Using nothing more than a screwdriver and crescent wrench, he removed the bad wheel, coaxed the holey inner tube from the tire, pumped in a little air, then plunged the tube into a bucket of water.

A knot of neighborhood kids usually gathered around the bucket, looking for bubbles spurting from the tube, the telltale sign of a leak. Next came the fireworks. A patch was positioned, ignited with matches, and, amid great smoke and drama, the leak was sealed. It was mild excitement on sleepy summer evenings. Because matches were involved, a dad had to preside over the proceedings. But as the summer wore on and flats became more frequent, the responsibility of setting the patch on fire was often passed on to the kid whose bike was undergoing the surgery.

The days of blazing patches are long gone. I suspect that the smoke from those fires probably contained toxic chemicals that are now causing all my midlife anxieties, such as the sweaty palm syndrome I experienced recently when I faced the challenge of fixing a flat on the rear wheel of a family bicycle. This bike, a three-speed Raleigh, wasn't exactly a top-of-the-line number, but compared with my old Western Flyer it seemed like high-tech to me.

Merely getting to the flat tire required negotiating brake clamps, cables and gearing mechanisms. I knew once I dismantled these gizmos, there would be the Humpty-Dumpty problem of putting everything back together again. At first I stalled. Rather than fixing the flat tire, I opted for what I call the "teen-ager's solution" to transportation problems. Namely, if your vehicle stops moving you don't fix it, you abandon it and quickly catch another ride. In my case I switched to another bike, one with two good tires.

Eventually, however, the guilt got to me and I vowed to make a run at fixing the flat. I found a couple of Web sites (totalbike .com and biketune.com) that provided background flat-fixing information and diagrams. Then I called Beverley, the mechanic, who passed along some tips and a philosophical overview.

Getting the rear wheel free of the brake clamps was easy. By turning a tension knob near the brake control on the handlebar, I was able to widen the distance between the two brake clamps, then slip out the wheel. Modern bikes, I am told, have levers to widen this gap.

My bike, which probably was manufactured in England when Winston Churchill was still prime minister, also had a wire-and-chain gizmo on the back wheel. It turned out to be a gearing mechanism named Sturmey-Archer. It looked fragile, but when I put the shifter into third gear and unscrewed the cable from the chain, it came apart without any fuss. I loosened the axle nuts - newer bikes have quick-release mechanisms - and soon the wheel was free of the bike, sitting on a table in my basement. As I prepared for the next step, getting the tire off the wheel rim, I heard Beverley's advice ringing in my ears. He was saying, "Don't muscle it, just Zen it." Rather than hurriedly prying the tire from the wheel by jabbing a screwdriver over the rim - "Never!" Beverley admonished - I took several cleansing breaths and, using the smooth handles of tablespoons, coaxed the tire from the rim. (Beverley said there are plastic devices called tire irons made just for this task.) Working slowly, with the spoon handles holding up freed sections of the tire, I eased the tire off the rim, then pulled out the flattened tube.

I couldn't resist pumping in some air and plunging the tube in a bucket of water. Ah, the sweet bubbles of my youth. Next I figured out where the invader that flattened the tube had penetrated the tire. This is what Beverley called "examining the deceased." The tire interior looked fine to my eyes. But when I gave it the feel test, I pulled my fingertip back in pain as it hit a tiny, virtually invisible metal shard protruding from the interior of the tire. It was the perpetrator. It drew some of my blood before I cast it out with a needle-nose pliers.

After a failed attempt at patching the old tube (I missed the spot), I bought a new tube and slowly put things back together again. The tire held air, the wheel turned without rubbing the brake, Sturmey and Archer went about their appointed rounds in proper, clicking British fashion. As I gave the bike a test ride, I felt a familiar sense of well-being. It was that mixture of accomplishment and wonder that washes over you, whatever your age, like the summer wind when you get your bike back on the road.