I was planning on making the famous TMB, "Tour du Mont Blanc" by bike ? Is it possible ? Is it authorized ? What are your recommandations ?
Yes, possible and doable. You don't need any particular autorization, except for you european id card or passport (just in case you are stopped by police). You can do it with or without a guide, there are several options, you can have mtb tour or a race bike tour for both there are several tracks freely avaliable on the internet and downloadable on gps.
It does need quite a lot of training cause you have around 7-8500metres of total uphill (depending on the tour. It can be divided in 2 to 5 days (or more as needed by the training level). There are reports of people doing it in 1 day but it's more that 300km or 16 hours of travel!! LInk to the tour in 1 day (italian)