[PatB]

Once you get in to banked track there are other forces in effect not just the grip level between tyres and track. If it was just down to tyre grip walls of death, the ultimate banked track, would never work

Although, on walls of death, tyre grip is still, apparently, important. I recall an interview with the guy running what was, I think, at the time, the last remaining one in the UK, where he mentioned that spectators spilling drinks down the wall could cause serious problems for the riders.