I don't have personal knowledge of MA laws on surge brakes, but they have been variously banned and permitted in many jurisdictions over the past few years as regulators tussle with the issue. Even if they are legal at one point in time, they may not be in the future. Also watch out for the regulations about crossing state lines (DOT doesn't like surge brakes, so there are reportedly issues towing across a state line even if surge brakes are legal in both states - perhaps that won't apply to you). Edit: I found the US federal law, and it was revised to allow surge brakes in 2007. Apparently some states changed their regulations to match that law.

Finally, check what the surge brake trailer weight limit is. There may be additional trailer weight laws that apply to you if you don't have electric brakes.

Surge brakes are great for one time use rental trailers. If I owned a trailer, I would just go ahead and get electric brakes, as they are lower cost, easier to maintain, and work better.

Good luck.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue