Sorry Dan,
My posts are currently moderated and in the time it’s taken for this post to appear, I’ve discovered the problem – my car comp was offset in time in the main comp – so the wheel animation was actually happening but much later in the comp – duh! Stupid but one of those thing that can take ages to track down. All working now – I love expressions, so cool when you get something relatively (for me!)complicated working 🙂
Many thanks for the reply though 🙂
Paul.