Rather than a large breaker bar, you might want to consider a torque multiplier instead. They're compact, lightweight, and with a 16:1 gear ratio, quite effective. Different models are available for different torque requirements. Harbor Freight Tools used to sell the inexpensive one that I carry with me in the RV, but now you have to go to eBay to find it. The only drawbacks are that it is relatively light-duty and that you have to brace the gearbox using an adjacent lug nut, and sometimes that can get awkward.
Inexpensive Torque MultiplierI also have a slightly larger one I keep at home that was purchased from Northern Tools. Although it's a lower ratio at 3:1, it is also heavier duty and can work up to 2,200 ft-lbs.
Heavy Duty Torque MultiplierIts operation is more straightforward and does not require you to brace the tool using an adjacent lug nut.