I will be going with my dad and my brother to Chamonix in the middle of Agust in order to climb Mont Blanc. After that I have about 4 weeks until I have to be back at university and would like to make a 'little' biketrip.

My idea was to cycle to Rome and afterwards stay there a couple of days before catching a flight back home.

According to Google-Earth is is 629 kilometers (390miles) from Chamonix to Rome, but this is if you travel by air. How much longer should I expect the journey to be by road? How difficult is it to find roads which I am allowed to ride on?

I think I can pull off about 100kilometers a day, which is 5 hours @ 20km/hour. Is this a fair estimation? Maybe I can do more?

Thanks a lot for any tips! Even if you don't know the area, any general tips that might help me out are very appreciated!