bigfred 

Your 23mm tires are undersized for your weight. This results in you needing to inflate them to abnormally high pressure if you are going to avoid pinch flats and a reduction in ride quality, traction and an increased probability of punctions.

For your weight 28mm tires really are more appropriate. However, some frames and/or forks don't provide sufficient clearance for such tires, even though they are once again becoming more popular in the pro peleton. Your frame or fork may limit you to 25mm at either end. Keep in mind that not all tire manufacturers measure their tires identically and some are commonly known to run a bit large. Michelin's 25mm tires in particular are well known to run in the 26-27.5mm range on standard 19mm wide rims. Where Continentals are know to run true to size or a little under with their 25s usually measuring very close to that and their 28s running just a touch under. Rim width also has an influence on the profile of an inflated tire as does inflation pressure and how old a tire is or how long it's been inflated at pressure.

One of the concerns with underinflated 23mm tires is the likelihood of pinch flats. Which can be identified by their characteristic snake bite pattern of a "pair of little holes at the same point on the tube" caused by the tube being pinched between the rim and whatever object you've collided with (stone, pot hole, pavement seem, etc.).