by sending him the wheels and him starting a disbupt, you kinda lose either way because now paypal will think you are the scammer by removing the money or if you didn't, they'll just take it away
the buyer should be able to change his mind especially since you haven't shipped yet. That's what the deposit is for. You having other commitments with the money should not be part of this transaction.
eg. amazon allows you to change your order given that it hasn't shipped yet