I'm currently car-free, but on occasion I will rent a car and take my bike on a road-trip.
My only option has been a trunk mounted bike rack. I bought an Allen Sports rack which works great.
But I have a few questions to those with experience with trunk-mounted racks.

1. When driving with my bicycle mounted on the trunk-rack , it is essential that I lock my front wheel to the bike frame (with my cable lock) to keep the handle bar and front wheel from turning from the vehicle's motion, as the wheel can often hit and rub against the paint of the rear bumper. The problem with this solution is that the force from the cable lock on my spokes from the vehicle's motion has bent one of my spokes. Is there another method of keeping the handle bar/front wheel straight while driving without the potential of damaging the wheel or spokes?

2. On many of the cars I have rented, it is nearly impossible to position the rack where the rack itself or the bicycle is not covering the visibility of the license plate.
I'm concerned about getting pulled over by a cop or even getting a ticket for this. I drive mostly in California, Oregon and Washington state.
Has anyone else been pulled-over for their bicycle or rack obscuring the visibility of their license plate? How did you handle the situation?
Is there any solution for this?

3. I'm wondering how a bicycle mounted to a trunk-rack impacts highway fuel economy of a compact or midsize car.
I have no means of testing this, as I often rent different vehicles and have no way to compare trips with and without my bicycle mounted to the car.
Part of one of my wheels does stick out and I'm sure that the aerodynamic wake is effected by the bicycle mounted behind the trunk.
I'm wondering if anyone has done any testing on impact to fuel economy with a trunk-mounted rack.

4. On my road trips, I often leave my trunk-mounted rack attached the trunk when I remove my bicycle to take a bike ride.
I am always sure to lock the rack to the car's tow hook using the same long cable that I use to secure my bicycle to my car.
I'm wondering if anyone has has their trunk-mounted rack stolen or vandalized when they left it on their car.

I use a Saris Bones rack. I use a bungie cord (the kind with a ball on the end) looped through the wheel and around the downtube to keep the wheel steady. I don't worry too much about blocking the license plate, never been ticketed for it and I have been driving for over 35 years. It will impact the economy but I have no clue how much, I would be surprised if it were more than a couple of MPG. I have never had a rack stolen or vandalized, but I did have the whole car stolen once with the bike rack in the trunk...

Aaron

1. I use a bungee cord to hold the wheel straight if needed.

2. Many miles and no issues with the cops. Same deal with the hitch rack I use. I'm more concerned with safety issues due to obstructing taillights and turn signals.

3. Not enough to worry about unless your driving thousands of miles. Even then, why worry?

4. There is no doubt that somebody somewhere has had their rack stolen or vandalized, but I haven't.

1. Often it's just easier to remove the front wheel.

2. Mine covers the plate also. I just don't drive around with the rack mounted sans bike.

3. Yes, roughly 2 MPG in my Mustang.

4. I'm not going to jinx myself with an answer.

Brad

As for fuel economy, I can give you a resounding "Don't worry about it." The whole mpg thing is ridiculous anyway. Consider this:

• If you get 30mpg and your fuel economy drops to 25mpg, that's a rise from 7.84L/100km to 9.41L/100km, 1.57 L/100km more
• If you get 10mpg and your fuel economy drops to 5mpg, that's a rise from 23.5L/100km to 47.0L/100km, 23.5L/km more.

Notice that fuel "economy" has nothing to do with fuel "consumption"? The whole miles-per-gallon thing is pretty bad at measuring this.

Point is if you're driving a 10mpg monster truck, you probably won't experience a 5mpg drop, or even a 1mpg drop; and it'll likely be much less of a drop in consumption than driving i.e. a Prius or a Porsche.

Besides, you don't even own a car. Don't think you're contributing anything even remotely significant, especially since you probably drive down greenified highways (trees planted everywhere) or down small roads through the woods.

1. I use a bungee cord to secure the wheels together and the bike to the rack.

2. I think cops realize this is something that it's difficult to do anything about; I've never been bothered.

3. On a trip last summer of about 4000 miles, I would say the bike + rack cost us about 3 mpg, from 29-30 to 26-27 ('03 Ford Taurus).

4. I know people who leave the rack on all the time; it's not anything that attracts attentions.