JF, Guys,
During the F-35 weight reduction effort all three variants were looking for pounds to lose and the landing gear came under scrutiny. (yes, should have been done during design first time around but LM didn't have a Chief Designer at that time and they took their eyes off the weight ball).
Anyhow, it was found that some conservative assumptions had been made for landing speeds, weights, temperatures, surfaces, runway lengths, repeated landings etc., which had led to fairly chunky wheel and brake units. On further examination, the LM team found some new tyres (I think they were French) that offered good performance with significant weight reductions. I think that they ended up with three tyre types for A B and C, choices driven by conventional landing weights/usage spectra. Brake units were also tailored across the three variants (remember that the F-35A and C had serious weight issues as well).
So, the main balance for F-35B was to provide the best possible conventional landing braking performance (and tyre life) while keeping weight down as much as possible, driven by the need to achieve the mandated Vertical Lift Bring Back (VLBB) figure.
Hope this helps a little
Engines