Bicycle racing and road touring is one of Italy’s favourite sports and drivers of cars are used to sharing the road with bikes.
In Tuscany we are not so well organized with many bike lanes in town but there are some help for bikers such as the
Bike park in Florence
Rent a bike services and restaurant for bikers
If you are for a self guided bicycling tour you can find suggested routes on books or ask the local Tourist offices for other itineraries.
Otherwise you can find many information online if you prefer organised and guided tours
Riding a bike is one of the best way to visit Tuscany and cycling is extremely popular here despite Tuscany being mainly very hilly.
For this reason in 2016 in Chianti we are going to have two of the most exciting biking tours:
The Giro d’Italia ( Tour of Italy )on the 15th of May 2016
The Eroica from the 28th of September 28 to the 2nd of October 2016 
Toscana Mia Blog 