from Newquay down all roads are like a magic carpet of bends and coastal  100mph straights 
  
  ( not that we ever do officer ;) ), ah actually if you just follow the coast road to st.ives its a good mix of twisties and a bit of A30, b ut be warned, it can be a bit muddy at this time of year, the full coast road from St. Ives to Lands End is hit and mix,get it on a good day with no coaches, O.A.P's, tractors and mud and its a great mix of 90 deg. bends and twisters, but meet any of the above either way and it becomes a boring slow slog. Better to head out of St. Ives on the Penzance road and then head down to Lands end that way, inland but just as twisty  and two lane all the way 

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Again when you head away from Lands End, head back towards Penzance and then choose your route, the south coast road is a good clear twisty road, but is peppered with speed limits, coppers with speed guns, O.A.P's etc, get it on the right day and time its a fun ride though. Otherwise head inland from the Penzance to Helston road, there are a variety of roads to take, B3280 to Camorne or carry on to Redruth, B3302 to B3303 to Camborne, B3297 to Redruth. To be honest pick up a visitors map of Cornwall and just pick out some roads, they are all a mix of twisted, two way but narrow roads. Or stick to the main roads and hope its a quiet day. Depends how long you've got and you can head back and forth across the county on a variety of roads, the choice gets wider as you head North, 
  
   as the county gets wider ;)