Just a quick story of my experience with a roof mounted bike rack:
I leased a Nissan Leaf when they fist became available and as I ride my road bike most days I thought the roof looked like a good place to haul a bike.
The first issue was the abysmal mileage I was getting with the rack, add the bike I was down to 53 miles a charge but I love the Leaf.
But that's not the worst part I had a ride in up in Sebring Florida (I am in Fort Lauderdale) obviously I cant take the leaf as it is over 200 miles so I was driving in the leaf with the bike on the roof to Fort Lauderdale airport to pick up a rental with
my mate who was going to drive the Leaf back to the office, we drive into the car rental area, as you enter the lane to take you to the car Rentals there is this big bright yellow solid metal girder across the road with big lettering Height restriction 7' or something, whatever it was it was lower than the bike on the roof.
When I hit it I thought I had run over those spikes they use to stop you going the wrong way..... BANG!!!!!
I say oh shi*t I blew my tires, my mate said no mate your bike is on the road behind us.
I had torn the bike along with the roof rack completely off the car.... massive damage to the roof good news the bike was fine as was the roof rack in fact the bike was still attached securely to the roof rack.
Moral of this story:
if your gonna get a roof rack buy an INNO if you want a tough road bike get a Cevelo and remember high restriction means you are to high if you are driving a Leaf with a bike on the roof.
(I got the Eco Hitch for my Tesla)