Roof Bike Mounts
Every roof bike mount requires a base roof rack (crossbars running across the roof) already be on the vehicle. Many newer roof bike mounts have ‘universal’ mounting hardware, meaning they will fit just about any crossbar on the market. But a lot of previous generation bike mounts only fit certain types of crossbars – Thule square bars and/or Yakima round bars. So be sure about fit before buying a rack.
Roof bike carriers are great since they’re out of the way, and are usually pretty streamlined. Note that this will require you to lift the bike up onto your roof, so if you have a heavier bike and own a tall SUV or other vehicle, it can be tough getting them off an on.
Hitch Bike Mounts
Every hitch bike rack must have a tow hitch on the vehicle in order to work. Hitch sizes are either 1.25″ or 2″ (larger vehicles more likely to have a 2″ hitch). Hitch racks are recommended for trucks and bigger SUV – since many already come with a hitch – and can also be used on sedans, wagons and hatchbacks after a hitch has been installed. Most common type of bike hitch rack, slightly less expensive than a platform style rack. Decent anti-theft options, makes contact with the frame. Less than ideal for carbon fiber frames. Irregular geometry frame dimensions (step-through, full suspension & children’s bikes) often require a top bar frame adapter for use with this style of rack. Largest models carry up to 5 bikes.
Trunk Bike Mounts
Pros: affordable, easy to get bikes on and off, doesn’t require a hitch or roof rack. Recommended for people with sedans or hatchbacks and who don’t plan to use it all the time. Cons: you can’t access your trunk when the rack is on, and getting all the straps in place can be fiddly (latest models are getting better at this!).