There are three main types of bike carriers; hitch mounted, strap on and roof mounted. Each comes with its own set of advantages and disadvantages.
These attach to a hitch at the back of the vehicle. There are two types.
• Class I carriers are compatible with a large number of cars and small Sports Utility Vehicles (SUVs). Depending on the design, they can hold up to three bikes.
• Class III carriers are designed for use with pickups and large SUVs. They can hold a larger number of bikes than Class I racks. Unfortunately, they cannot be used on smaller vehicles without expensive modifications.
These carriers are extremely easy to install, and there is generally less chance of accidentally scratching the paint off a vehicle while mounting bikes.
However, without proper installation, they can block rear windows, increasing the possibility of causing accidents while reversing, or cover license plates, which is considered illegal in many jurisdictions.
Strap-on trunk-mounted racks
These carriers are attached with straps to the trunk, rear bumper or hatchback, and carry up to three bicycles. They come with padded or plastic-coated frame supports to protect the bicycles from scratches and other damage.
Strap on racks are cheap and easy to store when not in use. They are also versatile, and can be used on virtually any model, which makes them particularly suitable for leased vehicles.
Unfortunately, like hitch-mounted racks, they can block the rear window if installed poorly. They are also less secure, as it is possible for thieves to untie or cut straps attaching bike racks to the vehicle.
These are attached to the vehicle's upper door frames or rain gutters, or where available, cross bars or roof racks, which is generally cheaper. Depending on the size of the vehicle, up to seven bicycles can be carried. A special case can be added if extra storage space for tools and other equipment is needed. When it is not being used for holding bikes, the rack can be also used for carrying canoes and skis.
While roof-mounted racks guarantee unobstructed view from the rear window, they are more difficult to install. Other disadvantages include increased air resistance, which can lead to increased fuel consumption and wind noise, and the increased likelihood of scratching paint as bikes are lifted onto the vehicle roof.