Unless you have a large station wagon or SUV, it's inconvenient to stash your bikes in your vehicle when you want to go for a ride somewhere away from home. And even if you do have a large vehicle, putting your bikes in your car isn't going to work when other people are along for the ride, or when your bike is covered with mud from a mountain bike trail. That's where bike racks come in handy, allowing you to secure your bikes to the outside of your car. Racks come in multiple configurations, including trunk-mounted, roof-mounted and hitch-mounted varieties.
Inspect the straps of the trunk-mounted rack to make sure they're all attached, and that the straps are of a relatively even length. The metal and rubber "hooks" at the ends of the straps should be tightly hooked around the top, side and bottom lips of your trunk or hatchback, though keep in mind that when you put the bikes on the rack, their weight may require you to tighten the straps even more.
Set the horizontal bar of your bike's frame -- stretching between the seat and the handlebars -- into the grooves along the horizontal bars of the rack. The bike should be evenly spaced between the two grooves, so that the bike's weight does not lean on one side or the other.
Wrap the straps near the rack's horizontal supports around the horizontal portion of your bike's frame, thus securing the bike to the rack. The straps may have hook-and-loop enclosure tape or may be made of rubber that needs to hook around a T-shaped piece of plastic, depending on the brand and model of rack you have.
Inspect your straps once you have your bike -- or multiple bikes -- secured to the rack. You may need to grasp the ends of the straps to tighten them, if they've gotten a little loose.
Inspect your rack to determine whether you have the type that requires you to remove the bikes' front wheels. If your rack doesn't have a large curved "hook" near the front of the rack, but instead has a cylindrical, skinny cross bar or a T-shaped apparatus, it means you'll need to remove the front wheel.
Set the bike into the "tray" on top of the car, with the front of the bike facing forward. If you have the type that requires removal of the front wheel, set the grooves at the bottom of the bike's fork into the apparatus at the front of the rack, and then press down on the clamp to secure the fork to the apparatus. If you have the type that doesn't require removal of the front wheel, pull on the curved or U-shaped hook at the front of the rack, and wrap it around the front tire. The hooks are typically spring-loaded so they'll secure tightly to the tire.
Wrap the rubber or hook-and-eye enclosure strap at the back tire around the back tire and tighten it down.
Inspect the rack to determine which type of hitch-mounted rack you have. Some racks have a tray near the bottom, allowing you to set the bike into the tray; others require the bikes to hang from near the top of the rack and be strapped down.
Set the bike's tires into the tray near the bottom of the rack, or set the horizontal portion of the frame into the grooved rests near the top of the rack. The bike should be evenly spaced so that the weight is evenly distributed on both sides of the rack.
Wrap the rubber or hook-and-eye straps around the frame of the bike for a rack with grooved rests at the top. For tray-mounted hitch racks, you may have a curved, spring-loaded hook to wrap around the front tire, and sometimes the back tire as well. Typically, you'll have a strap to wrap around the back tire as well.