Fair point, I assumed that as it ran along a track it was a type of monorail, but the tyres don't fit that description! I'm usually observant, but can only think that most times I arrived by train and went straight to the shuttle and the gates, or did I check-in in the main terminal ?? Whichever, I didn't really notice the wheels and tyres :-)
I think my first flight from the satellite was an American Airlines 747/DC-10 to DFW in 83 and the last that I can remember was a Dan Air 737-400 in the early 90's, though I must have taken flights from there since then, but too nondescript to remember. I'm not sure when, but at some point there was a bilateral agreement that allowed the main US carriers to fly into/out of LHR , and LGW was abandoned en masse by the major players. Possibly British Airways started flying long-haul scheduled from LGW around the same time, though not from the satellite.