>> Tow bar mounted racks are very convenient, and keep the crap falling onto
>> the roof of your car, but they make a big dent into your fuel consumption…
> Yes, but no more so (probably less) than having them on the roof.
Nope; a towbar rack provides a significantly more drag than a roof rack. I own both, and the difference between the two is palpable. As a simple exercise to demonstrate why, next time you ford a river with your bike, check the difference between placing the bike in the direction of flow and then across. 🙂