I've ran 3 9XLs on 5s lipo, geared for 40mph; didnt last more than a few runs each time in my 13lb GorillaMaxx, they just arent that great really ( regardless of specific brand ). Keep an eye out for bargains though as used Neus and CastleNeus pop-up all the time, along with new brands or revived brands like Medusa ( for sale on the Neu website ).