I know a GRIP of places, the funnest part is just exploring to find your own spots, but a couple id be more than happy to share with everyone include Gilbert rd south of riggs its all farm land and all of the roads are MAINTAINED dirt so you get the pleasure of dirt with the safety of asphalt. Another good one that has been mentioned is South Mountain, BUT slightly modified... on weeks nights at like 2 AM there is no one out including cops and you can drive to the entrance and you'll notice on one side is a gate and the other side is one way road spikes, if you get creative and use your imagination its like having South Mountain as your own personal test track, i wouldnt suggest on weekend because im sure im not the only person in the world whose ever done it and id hate to see someone drive off the side of the mountain. Lastly if your wanting to see how fast your car will go i suggest going on elsworth to pecos the from elsworth east on pecos you have like 1.5 mile road that almost no one uses late at night... The last place and least riskiest and scenic drive i suggest would be the 88 or apache trail to canyon lake, its always a good time and if you continue it turns into a dirt road a few miles after canyon lake. HAVE FUN and be CAREFUL!