Join Date: Feb 2004
Location: St Peters, Missouri
Bikes: Rans Rockst (Retro rocket) Rans Enduro Sport (Retro racket) Catrike 559, Merin Bear Valley (beater bike).
There's lots of different parts to your post.
1. You need to check on your factory roof rack rails. Some aren't attached to the car securely enough to carry bikes.
2. I assume that you're talking about installing aftermarket cross bars, like Thule, to your factory roof racks. That might be possible, but the clips to attach the crossbars might not be the same. If the clips aren't the same or if the bar spacing is different, moving the rack system from car-to-car will be a major project.
3. I used to remove the roof rack system from my Saturn in the fall and store it in the garage over the winter. I removed it whole, crossbars, clips, bike holders and wind fairing all assembled together. I could just manage to do it by myself, but it was a lot easier with a helper. It was only about a 5 minute job.
4. On my Saturn sedan, a dinky little under powered car, the gas mileage penalty with the bare rack on the highway was around 7 MPG. The penalty with bikes was about 10 MPG. I'm told the difference is much less pronoumced on bigger cars with more reserve power.