Hello, I have Cinelli 2a stem and some Cinelli Pista bars. The bars are great but the angle is too steep for me. I want to get a 100mm 1a and some new bars, probably the giro D'italia. Can you guys enlighten me on the compatibility of these two different set ups? what are the clamp diameters for 1a and 2a and what are the diameters for the pista bars and the road bars? are the road bars (cinelli) all standard in their diameter? also the pista bars just say pista, but the Giro d'Italia say 64-40, i read that the first number indicates that its the model (?), so 64 is all giro d'italia's (?), but what does the second number mean? thanks in advance!

Cinelli 1a stems are hit and miss as far as clamp size, some are 26.4, some 26.0, same as the Giro bars.
The bars will have a warning on center section usually saying 26.0 as most are 26.4.
64 denotes model, 40 is the width.

+1 on this one. Back in the day we reamed the stems to from 26 to 26.4 to play safe, is 2 or 3 turns with the adjustable reamer and ready to go.

U have to measure man, not other way.