I tried putting a Thule roof rack on the car so I could go mountain biking. The car did not like the rack at all. My mileage went down to 45/46 mpg without the bike on the roof, more like 40 mpg with the bike on the roof. And the battery pack would routinely be at 50% which is very rare unless climbing into the hills. So, I got a trailer hitch and a hitch mounted bike rack and my mileage is back to normal with no bike and higher than the roof rack was with the bike. So, yeah, by a trailer hitch for your Civic Hybrid.
The 52cm road bike fits in the back seat with the front wheel off. There is lots of room for a longer bike, but the rub would be the driver's seats - mine are far forward.
I didn't try it in the trunk but I'm sure it would fit with both wheels off.
I am thinking of getting a hitch rack - I'm not going to want to put a dirty cyclocross bike in the back of my new car.
Re: Can you fit a road bike in the 2k6 HCH?
