Terrific to see you are getting out Nin and putting the awesome bike you built to good use. Top marks!
Here is some info on alpine routes that may be of use to someone:
Parpaillon: very nice, easy to ride and amazing views all around. DF (dificulty factor from 1 to 10, 10 beeing almost impossible) 5 to 6.
Valbelle/Cloch: Less interesting, though still a nice track, do take the track to the viewpoint Belvedere de L'Homme de Pierre. DF 5 with a section (about 1km) of 7.
Moutire: tarmac from St. Dalmas to the intersection, from there it's an easy trail to the Bonette road, or a much less easy trail down to Bayasse, on the road to Cayolle. Great views, nice track to ride. DF 6 to 7.
Tende, the old road on the northside: Loads of hairpins, some not so easy to handle. Great views when the weather's any good. DF 5 to 6.
Via del Sale, also known as Ligurian ridgeroad: an 80km long stonetrail, which is best to start at Col de Tende and its Fort Central. Starts easy, but within a few km's you'll receive the toughest stretch of gravel/stonetrail you've probably ever ridden. From Col de la Boaire to Col des Seigneurs, it's nothing less than hell, but if you make it through, you'll feel king of the world. Going back down the valley using Pass du Tanarel, near Monte Saccarel, might be a bit tricky too, watch out in the woods, the trail might be slippery, since there is no sunlight. Amazing stuff, and probably the most challenging stretch of gravel/dirtroad in the Alps. Make sure you start real early, 'cause it takes an entire day to ride. DF goes from 5 to 9!
Sommet Bucher: A dead end trailroad going up to a 2257m high point of view. Easy to ride, the view is nice. Starts in Chateau Queyras, take the bridge across the river, and take right, into a narrow gorge. DF 3.
Assieta routa di cresta, or ridgeroad: Really nice trail, not difficult, starts in Sestriere, the hardest bit is going up Col Basset, from there it never gets any harder, so no panic. Great views al along the trail, you can even see the track to Fort Jafferau. DF 5 to 6.
Sommeiller: Known from the Stella Alpina, though not many reach the summit then, since the road is most likely to be covered in snow. Some hard parts, which can make you wonder to continue, but do, since it's the highest you'll ever gonna get in the Alps on a bike. Great views along the way, the summit itself is not really special, but still, you can walk to the flagsposts, and you'll be over 3000m high. Just because it's the highest do it anyway, but it's worth more credit than that, it's a real nice trail, which leads you up to the Glacier Sommeiller. DF 6 to 8.
Fort Jafferau: Most beautiful trail in the Alps. Great views all the way up, don’t forgot to go and see Monte Pramand though, scary tunnel section which is never dry, and not so hard to ride. Highly recommended, DF 5 to 7.
Forcella Lavardet: Easy to ride dirt/gravelroad on the northside of this pass. Starts in Campolongo, than a gravelsection, than a tarmacsection with the famous hairpins going up the mountain, than agin it's gravel, and the famous "concrete tunneled bridge" up to the top. Nice and easy to handle, don't go there when there's a rainstorm, 'cause the track is right next to the river. DF 5.
Pla de Beret/Montgari/Allos d'Isil: Easy to ride trail along the river La Noguera Pallaresa. Go up to Pla de Beret, continue straight, and at the last skilifts, the trail starts. About 35Km, great views of the Pyrenees, some watercrossings but nothing to panic. DF 4.