501 wheels
 

As title says which wheels fit - the set on the car don't have tamiya logo's on but my rear TRF201 wheels do fit on the back end 'pins' but the front end has a hex?

I think you can use the same as for the 502X:
51320 DB01 White Dish Wheels (Front/White)
51321 DB01 White Dish Wheels (Rear/White)
51304 DB01 Black Dish Wheels (Front)
51305 DB01 Black Dish Wheels (Rear)
53985 TRF501X Front Dish Wheel (Yellow/2pcs.)
53986 TRF501X Rear Dish Wheel (Yellow/2pcs.)
54282 DB01 Front Dish Wheels (Pink)
54280 DN-01 Rear Dish Wheels (Pink)

And yes, the front wheels has a hex.

Best regards

You can also use the Losi XXX-4 wheels (front and rear) as well.

They were what I used to run on my DB-01 (same shallow hex wheel fitting as the 501 on the front and pin drive rear) as they were easier to get hold of in the UK.