Changing 23mm tyre to 25mm - considerations? I got a L size Opus Allegro 4.0 (2014) which came with Vittoria Zaffiro tyres 23-622 (700*23c) on an Alloy Shimano Asoo WH-R501 wheelset 622x15c. I'd like to fit a wider tyre to improve my experience and feel when I am on bumpy roads. 

I'd like to know what parameters I should consider when I fit a wider tyre (say a 24 or 25) on the current wheels/innertubes and, what are the limitations of my current set up if I don't want to change all at the same time (i.e., bike frame, etc.)
The two things to consider when increasing tire size are compatibility with the rim width and frame/fork clearance. Inner tubes fit a range of tire sizes. 

15mm rims will easily take 23 or 25mm tires. Check that your frame has sufficient clearance for an extra mm or two on either side (some tires are a bit wider than specified width) at the brake calipers, fork crown and chain stays. I'd be very surprised if the frame does not have clearance for 25mm tires.