a bike helmet would be fine for track, its only if your in a team you must have full car spec helmets OMP do them but there just black with a like yellow OMP sticker at the back i believe no quite a few people who just buy black helmets and put a little sticker on them lol. The ones for cars are made differently oddly they are stronger then bike ones and i think use flame proof material. All makes of helmets have different fitments your better of going to a bike shop and trying them on.....there is a good on in GY call rob speeds as well depending on the foam you might find a slightly smaller one better as if its soft foam after a few wears it will start to move above helmets should always be snug at first