Maintaining Your Bike
Flat tires and crappy brakes suck...but they're preventable. Check your bike at the beginning of your ride to avoid mechanical brake-downs (oh, we're so funny). If you can't get your bike working, check out your owner's manual, a maintenance book, or a bike shop. We can't keep emphasizing bike shops; aside from you, they're probably your bike's best friend.
Tires lose a little air every day. Check your tire pressure with a gauge before each ride. If the gauge says that a tire is more than five pounds under the recommended pressure (printed on the side of the tire), add air with a bike pump.
A dry chain can skip, lock up, or break suddenly. If your chain squeaks or hangs up, lubricate it. Oil will do, but it attracts dirt; a greaseless chain lubricant is cleaner. In any case, make sure you lube often, especially after riding in the rain.
Grab the bottom of the chain loosely with a lint-free rag. With the other hand, turn the pedals backward, sliding the chain through the rag. Pedal the chain around twice to remove surface grime.
With one hand, squeeze or spray lubricant onto the chain. With the other hand, pedal the chain backward so it goes completely around once.
Repeat the first step to get the excess lubricant off the chain. Extra lube can attract dirt.
Lift up each wheel and give it a slow spin. Spin the back wheel forward so the pedals don't move. Make sure the wheel doesn't rub against the brake pads, frame, or anything else. If the wheel doesn't spin freely, but it's not rubbing against anything, the problem might be inside the axle. Ask your local bike shop!
Turn each wheel slowly and look for big cuts, bulges, bubbles, or places where you can see the inner casing. If you spot any, replace the tire. Remove glass or other debris. Make sure the tire is seated evenly on the rim. If the valve stem doesn't point straight at the middle of the wheel, the rim might cut it; let the air out and straighten the valve.
Try all of your gears, shifting each gear lever from high to low. You have a problem if the lever sticks, you can't shift to all gears, or if the chain rubs or jumps off the gears. These are usually caused by worn or dirty cables, or gears that need cleaning or adjustment.
Hold the front tire between your legs and try to turn the handlebars. If they're loose, tighten the stem bolt.
You should have your brakes adjusted or replaced if you have any of these problems:
You apply the brake on each wheel, and one or both brake pads don't touch the rim.
You can squeeze your brake lever all the way to the handlebars.
On each wheel, the brake can't stop the tire from moving on dry, clean pavement.
The brake pad doesn't spring back from the rim after releasing the brake lever.
Pick up the bike and shake it hard. Check and fix anything that rattles. Or ask your bike shop to fix it. They're good that way.