Peter,
petermmc wrote:By the way, I realise you are an eager car racing photo enthusiast. If you were taking shots of dirt bikes moving how would you set your D70 up for focus. AFC and Dynamic or AFS Single or other variations?
Depends.
One very useful technique is to prefocus on an area where you know the cars/bikes will be going by. Leave the camera on manual focus and prefocus on that spot. When they go through that area, just press that little button.
If you have reasonable weather conditions (meaning consistant lighting conditions) then it also helps to take a meter reading off something that's equivalent to an 18% grey card, and set your exposure to manual, using the settings acquired from that reading.
FWIW, I'd expect that a dirt road would be a rough equivalent of an 18% grey card, so if you have good bright sunlight with little cloud, or lots of cloud with few breaks, that sort of metering should work well.
If you have intermittant cloud cover then that makes it a bit toughr, both from a metering and a WB PoV.
But getting back to your question, if the vehicles are moving towards or across you, you could also try dynamic + continuous AF.
What lens stock do you have in place for this? if there's a travel limiter, such as on the 80-400, be sure to set it, and, of course, at the far end of its range, to limit any hunting and help improve its responsiveness.
And to further help that, before the vehicles come into view, again prefocus on a subject that's a similar distance to tjat which the vehicles will be at before you start to follow them. Then, only start to follow them when the lens already has them in focus as they move within your frame. This is another trick that should help reduce hunting for focus and thus improve the apparent responsiveness of the lens.