I noticed some residual air pressure in the radiator the day after riding. The radiator hoses seemed slightly stiffer than normal. When I removed the radiator cap, there was a release of some air pressure. I have not noticed this before. Is this normal? Maybe when I recently drained the cooling system and re-filled it, there was some trapped air inside that had not escaped?

 

Could be a possible air bubble that didn't "burp" out. There is usually a bit of residual pressure until the system is totally cold. I wouldn't worry unless it is running extremely hot or blowing coolant into the overflow tube. Just keep an eye on it.