Associated springs for me, as they have a good range and they fit better than Losi one's. I will be getting an ally chassis on release, as I prefer a more rigid chassis set up.
Tungsten balls come with the diff and they are ultra smooth, just tighten the diff up and let them bed in. My MR diff hasn't been rebuilt all year and its still ultra smooth. Last year I put ceramic balls in my old B-Max2, ran them a little looser but not slipping and they lasted two meeting before needing a rebuild, went back to the old tungsten balls and they are still in there
