I drove my X yesterday for five hours without a break and I must say she went very well with only one concern; the brakes started to vibrate when hot. I can understand that there will be expansion and contraction but I cannot understand why that would be assymetrical, which it clearly was as I could feel the brake pedal pulsating, and this went away as the brakes cooled.
For the brake pedal to pulse, the shoes must be contacting the rotating drum intermittently, as you noticed. It can be a few things causing this, oval drums possibly caused by heating, but also shoes moving too. If the shoe lining is lopsided, you'll get reactions as the surface contacts the drum, and shoes can vibrate too. Unfortunately if the drum is distorting when getting hot, and the drum thickness is the same, there's not a lot you can do, as I don't know anyone who does a "hot" regrind of a drum.
