There are a lot of good reasons for having a bike in Bologna, the first of which is convenience. With a bicycle, nothing in Bologna is really more than 15 minutes away from the center, even the Fiera.

Ask at bike shops to find used bikes for sale. See the listing BICICLETTE in the yellow pages:
www.paginegialle.it

You can also check the classified newspapers. You can also check the Piazza Grande association's warehouse of second-hand goods - sometimes it's possible to find reconditioned used bikes.
Piazza Grande
Address: Via Libia 69
Tel. 0039 051/342328

Spend as little as possible for your bike, but buy the best lock you can find in ferramenta (hardware shops) all over the city.

BIKE RENTAL
-STAZIONE FS Piazza Medaglie D'oro 4/a
(inside the railstation, in the moto and bicycle parking)
tel/fax 0039 051/251 401

-TANDEM Strada Maggiore, 90/c
tel. 0039 051/308830 Mon-Fry. 8.30-12.30/15-19; sat-sun. Closed
To getting to: by car, gate n. 11 of tangenziale direction "centro"; by bus line n. 14, 19, 25, 27, C.

-DUE RUOTE Via S. Stefano, 14 4
tel. 0039 051/233337 
fax 0039 051/233337
Mon-Sat. 8.30-12.30/15-19; Thu. - Sun closed.
To getting to: by bus line n. 11, 13, 14, 19, 25, 27, 90, 96,

For more information in English language, look at the page of IAT (Tourist information):
urp.comune.bologna.it/IAT/IAT.nsf/328659196175c4d0c12567fa0054d77e/744cccc1ebca96cdc1256bab002b05c8?OpenDocument