The choices of car rack location on your vehicle MAY include one (or more) of the following.  THERE ARE some vehicles to which you cannot safely attach a rack!

FRONT BUMPER RACKS

• More versatile, safer carrying location for both bicycles and cars.
• Can be clamped and locked onto the top of nearly any vehicle.
• The best ones use specially-manufactured clamps and hook attachments to securely custom-fit the rack to your roof.
• Provide a strong platform onto which bicycle (or ski, canoe, cargo box, etc.) carrying attachments can be mounted.
• Protects bikes from scratching each other with wheel trays and clamps that hold bikes upright and separated.
• Carry heavier weights and the largest number of bikes (usually at least 4, and up to 14 depending on vehicle roof size and weight limitations).
• Lock bikes on very securely with all locks even using the same key.
• Bike-carrying attachments may adapt to your vehicle’s manufacturer-installed roof rack, BUT THAT RACK’S WEIGHT-CARRYING CAPACITY IS OFTEN LIMITED. Check your owner’s manual or with your car dealer for limitations.
• Small ladders may be necessary to reach a higher vehicle roof.
• Often cost more (the price of versatility!) than other bike racks.
• If unsure about proper installation, please ask!

• Most frequently used location offering the widest available variety of racks.
• Energy-absorbing car bumpers mostly eliminated use of racks that could be hooked or bolted onto bumpers. Only a few kinds are still available.
• Most racks fasten to the rear of the vehicle using three, four, or six adjustable nylon straps with plastic-covered metal ends (that hook to the top edge of the trunk lid, under the trunk lid or bumper, and sometimes to the sides of the trunk lid).
• Always fasten strap-on racks securely by pulling straps tightly through their buckles and clips. Re-check strap tension after bikes are loaded for any loosening.
• Most strap-on racks carry 2-3 bikes. 4 bike models are available.
• Rear trunk spoilers, soft bumpers, one piece fiberglass rear ends, and large, glass hatch backs can make use of strap-on racks difficult or impossible.
• Strap-on racks are more likely to scratch bikes put too close together. Protect frames by using pieces of foam pipe insulation or foam blocks between bikes.
• Hook-ended bungee cords are handy for fastening bikes to racks.
• Bikes should be secured to rear racks in a manner preventing their: 
• “Flapping” against each other or the car.
• “Bouncing” up and down on the rack.
• Falling off the back of the rack.
• Hanging down so low their tires could bottom-out on the road.
• Tires melting from being too close to hot car exhaust pipes.

• Extremely popular on sport utility vehicles, vans, and vehicles having nowhere else to mount a rack.
• Racks have 1 ¼ inch or 2 inch square mounting posts that insert into a square pipe bolted to the underside, rear of your vehicle
• Easily installed and removed, and most have 2 to 5 bike capacities.
• Most tilt down WITHOUT bicycles on them for use with tailgates and rear doors.
• Models that tilt while LOADED require load-compensating pistons to handle the weight, and are more expensive.
• Some designs make mounting a “lady’s” bike frame difficult.
• Some have mounting trays (similar to roof rack bike mounts) that bikes stand upright in, parallel to the rear of the vehicle

• Either clamp onto a hitch-ball or bolt through the hitch-ball mounting hole on the bumper or hitch tongue.
• Usually can only carry 2 bicycles due to weight capacity limitations.

• Some roof mount racks have adapters to clamp them onto a camper trailer roof to use as you would a conventional roof rack.
• Camper ladder-attached bike racks are available.
• Bolt-on or clamp-on bumper mount racks may fit rear camper bumpers.
• Receiver hitch racks are made that “sleeve” over a camper trailer “tongue” (in the space between the rear of the car and the camper trailer), allowing two “uses” of a receiver hitch at the same time.
• It’s possible to use strap-on rear racks on some campers.
• Some people tie bikes down on their camper roof, but this can dent a camper’s fiberglass or vinyl roof.

• Easy removal of one or both of the quick release wheels on many bikes lets you easily put your bike(s) INSIDE your vehicle, eliminating your need for a bike rack (As long as you aren’t carrying a lot of people or gear inside, too.).
• Bikes transported inside vehicles minimizes their likelihood of damage and/or theft from a rack.
• Rods or bars that mount across the back of a pick-up truck bed with quick release brackets on them to hold a bike’s front fork (once the front wheel’s removed) are available, and usually hold 2 bikes.
• (Inexpensive) quick release mounting brackets are also available that bolt to the floor, sidewalls, or to a piece of lumber laid across the floor of your truck bed. Purchase a bracket for each bike you want to carry.

• Due to strength limitations of the mounts on vehicles that hold spare tires, these racks can only carry 2 bikes.

• Most can be adjusted to "center" your bike load in the middle-rear of your vehicle if your spare tire happens to be mounted to the extreme left or right of your car.  

• Most have folding or collapsible arms so the rack doesn't protrude outward from the back of your vehicle when you don't have bikes loaded on it.

• Some racks hook and strap onto the wheel and tire on the outside back of the vehicle.  These WILL NOT fit many vehicles (like late model Jeep CJ7's) with brake light brackets that stick-up over the spare tire.

• Some racks use a mounting plate that bolts onto the lug bolts to which the spare tire is attached.  These mounting plates have a protruding attachment point into which the bike-carrying part of the rack sleeves, similar to the way a receiver hitch rack works.  These may be your only choice if you have the "light" problem mentioned above.

Here's some links to the most popular bike rack manufacturers