Hello. I had just bought a set of full carbon clincher wheels that measure 20mm (outside to outside). They did not come with tire size recommendation so I am not sure if it is fine to use my Michelin Pro 4 23mm tires or will I have to purchase a narrower tire like a 20mm-22mm? I am just concerned about the safety and the impact the wider tire might have. Thanks to all that can give me advice.

Here are two guides that you can use to select the right tires.

The first relates tire to rim width (inside rim width is what counts, so measure your rims (or subtract 3-5mm from the outside width depending on the thickness of the outside walls. You'll see that anything from about 22mm to 28mm will be fine, assuming the larger tire clears the fork.

This one discusses optimum tire width and pressure based on rider weight. use it to calculate optimum pressure for your weight and riding conditions. I prefer keep 105psi as the pressure ceiling and ride the width that's best at that pressure or less.

Running a 23mm tire on a 20mm rim should be no problem. In general, the limiting factor for tire width is usually frame clearance, not rim width.

thats what i was just thinking. unless you are trying to run the skinniest tires possible then thats determined by the rims inside measurement

700x23 is pretty much the default size for almost all sporting/racing clincher tires. The narrower 20 mm and even 18 mm tires that used to be available have pretty much disappeared from the market. Wider tires like 25mm are used by some fitness riders and even wider ones like 28, 32 and more but are generally used on touring bikes or for rail trail riding.

Thanks to everyone for their input and the usefull information.

I've been running a 42mm wide studded tire on an open pro rim(20mm wide) for years with no issues. I feel as hough these combinations require more care with tire pressure but in your situation my guess is that frame/fork clearance will become an issue way before you need to worry about that.