I don't know if you're still struggling with the NASCAR event, but here are my two cents:
The NASCAR event in GT5 is just like cross country skiing: There's no point in going up in the lead unless you have a good chance to get a gap and to keep that gap until the end of the race. All you will end up doing is acting as a rabbit for the rest of the pack to hunt down (and sometimes even kill).
It's better to lay low for a while, watch how the race is developing and then when there's a good opportunity to make a move you go for it. If you don't get a good opportunity, just lay low until the final lap and try to have a good position within the pack, then right before the last corner you use the slipstream to get up in the lead to cross the finish line as the winner.
Hi thanks for taking the time out to assist me, I have tried this nascar one so so many times staying low staying high holding back I just don't think I am good enough to do it if I am honest. I tried the holding back was in forth if memory serves me right overtook on the last bend and got smashed off by an ai which nudged me in the rear I had two ai cars behind me one to my left one to my right so I tried to block the quicker car , I thought at the time that nudge would not normally knock me off track but it did, Oh well some races I had to quit and give a miss and the nascar race is one of those races. Not been on this race since that grand failure, doubt I will go on it again as my outlook on gt5 now is have fun and enjoy it. Nascar isn't fun to me so best I avoid it. Thanks again bud.