At all the tracks that I race at in the UK, they have always been clockwise orientated, so the outside tyres will be the left hand side of the chassis. I run a set of tyres per heat and final, so that's 5 sets. They get rotated from left to right depending on which tyre out of the pair are bigger or smaller diameter. We don't get much time between heats so the first thing I do after a heat is to change tyres, get additive on them, change cells (forgot to do that a couple of times in the past!) and then check for repairs/setup changes. Do like the technical side of RC racing though, hence questions like this have an intrest to me, haha! Cheers, Chris.