Hmm. Not sure what the best approach is for this. I assume that the shots are done on a purely speculative basis.
Do you have to send proofs out. This does tend to take the advantage away from you when it comes to selling, and may not yield a high return. Are you sending more than one picture ? Can you pre sell the pictures, That's not easy I know.
If they have more than one picture to choose from you could try making up a montage on a print 5" x 7" . Tell them that's the size of the print they will get and ask them to choose which Pictures they want. Always assume they will want more than one. Also offer a discount if they return the order within say 7 days.
You might be able to do a display at the track, but I suspect the organisers/owners may want some money or percentage for giving you the space. However you might be able to do a contra-deal by providing them with pictures for magazines. It may be worth asking.
The alternative is to sell off a web site, but that may involve costs you are not willing to spend at the moment, without an idea of how successful things may be.