Check out SARIS BONES. Great if you dont have a tow bar. Have used one of these for a few years on various cars and SUV's. Come in 2 or 3 bike versions.

My Treg has the rear wheel on the back so I use a bike rack that mounts onto that at the moment.

 

I use roof mount racks. I've got an older version of this RockyMounts Euro tray for my Specialized and have a second rack that's a really old version of the Thule Big Mouth for my wife or brother's bikes that don't have the quick release front tire.

 

If you are into downhill mtn biking northshoreracks.com makes a nice one for 2-6 bikes and they make it easy to load all sorts of different frame types because of the design. I use a hitch mount Thule That holds 4 and has an integrated lock cable which is very convenient. I'm not a big fan of the roof mount units myself, maybe if i had a nice light road goer. Good luck

 

I purchased a Thule 4-bike carrier...nicely constructed...hitch receiver tightener, integrated locks for the hitch and bike, adaptor for smaller hitches. You need to add carrier bars for women's or kids bikes to provide a level hanging point. A bit pricey, perhaps...400 - 500 all in...but I won't ever buy another. Ever.

sold everywhere...etrailer.com. EMS.com.

Now if spring would ever arrive....

I am actually in an another place...with such a nice hitch, I need to get a nicer bike.

 

To the OP... You don't say if you have a hitch. Keep the bikes OFF the roof if at all possible. Just an annoyance, unless you are well over 6 feet tall, and it will still be annoying.

If you have a hitch, get a rack system that is light, and doesn't require the wheels to be removed. Just lift the bike on and lock the wheel or frame...Done....

I sold my 10 year old Saris Cycle On Pro last year, and bought a 1upUSA with add-on for two bikes. I can carry either one or two bikes. It installs VERY quick about 2 minutes. It holds the bikes by the front and rear wheels, so no problems with frame sizes or shapes. It will also hold road bikes , or DH bikes, tire size or diameter don't matter, and they are aluminum, so no rust (my Saris had steel trays, and they had to be repainted a few times to protect them, and the galvanized springs for the release mechanism rusted out and I had to spend $200 for new arms).

Even though most tray carrier systems cost well over $200, it is worth it considering the ease of getting bikes on and off from a hitch mounted system, no mud on your roof, no driving into a drive through or garage by accident with a bike on top of your vehicle, and most new road and mountain bikes cost well north of $1000 (mine was $6400).

For roof racks, someone already mentioned the Thule Side Arm, I have these as well. They work, but I needed a small step stool to make it happen because of how high on the roof they are. Not easy, but a good solution when towing a camper.

 

Thule bike rack works great. I would not even consider a roof rack. Built in lock, replaceable bike supports and ties. I also use a lockable hitch pin to prevent the entire rack from removal. This rack also folds down for clearance and access to truck if necessary.

 

Check out Arvika at Racks for Cars. I bought one for 2 bikes after seeing similar styles in Europe.

 

Yeah, I probably wouldn't like the roof rack as much if I wasn't 6' tall already. But the roof tray carrier is way cheaper than a hitch mount setup. Plus, I like the park distance system to stay functional. And people are less likely to mess with your bike when it's well over their head vs right at arms reach.

Each has their pros and cons, just need to figure out what will work for you. If you're somewhat forgetful, don't put anything on the roof as mentioned above. If reaching the roof could be a problem, go for the nice hitch mount systems that will hold securely still and move out of the way for rear hatch access.

I've had good experiences with orsracksdirect, of you're looking for online retailers. Check your local craigslist or bike shops too, sometimes they have something used or discounted that will fit your needs and you could save some big bucks.